Advertisement

Increased Central Auditory Gain and Decreased Parvalbumin-Positive Cortical Interneuron Density in the Df1/+ Mouse Model of Schizophrenia Correlate With Hearing Impairment

  • Fhatarah A. Zinnamon
    Affiliations
    Ear Institute, University College London, London, United Kingdom

    Unit on Neural Circuits and Adaptive Behaviors, Clinical and Translational Neuroscience Branch, National Institute of Mental Health, Bethesda, Maryland
    Search for articles by this author
  • Freya G. Harrison
    Affiliations
    Ear Institute, University College London, London, United Kingdom

    Department of Neuroscience, Physiology & Pharmacology, University College London, London, United Kingdom
    Search for articles by this author
  • Sandra S. Wenas
    Affiliations
    Ear Institute, University College London, London, United Kingdom
    Search for articles by this author
  • Qing Liu
    Affiliations
    Unit on Neural Circuits and Adaptive Behaviors, Clinical and Translational Neuroscience Branch, National Institute of Mental Health, Bethesda, Maryland
    Search for articles by this author
  • Kuan Hong Wang
    Correspondence
    Kuan Hong Wang, Ph.D.
    Affiliations
    Unit on Neural Circuits and Adaptive Behaviors, Clinical and Translational Neuroscience Branch, National Institute of Mental Health, Bethesda, Maryland

    Department of Neuroscience, Del Monte Institute for Neuroscience, University of Rochester Medical Center, Rochester, New York
    Search for articles by this author
  • Jennifer F. Linden
    Correspondence
    Address correspondence to Jennifer F. Linden, Ph.D.
    Affiliations
    Ear Institute, University College London, London, United Kingdom

    Department of Neuroscience, Physiology & Pharmacology, University College London, London, United Kingdom
    Search for articles by this author
Open AccessPublished:March 16, 2022DOI:https://doi.org/10.1016/j.bpsgos.2022.03.007

      Abstract

      Background

      Hearing impairment is a risk factor for schizophrenia. Patients with 22q11.2 deletion syndrome have a 25% to 30% risk of schizophrenia, and up to 60% also have varying degrees of hearing impairment, primarily from middle-ear inflammation. The Df1/+ mouse model of 22q11.2 deletion syndrome recapitulates many features of the human syndrome, including schizophrenia-relevant brain abnormalities and high interindividual variation in hearing ability. However, the relationship between brain abnormalities and hearing impairment in Df1/+ mice has not been examined.

      Methods

      We measured auditory brainstem responses, cortical auditory evoked potentials, and/or cortical parvalbumin-positive (PV+) interneuron density in over 70 adult mice (32 Df1/+, 39 wild-type). We also performed longitudinal auditory brainstem response measurements in an additional 20 animals (13 Df1/+, 7 wild-type) from 3 weeks of age.

      Results

      Electrophysiological markers of central auditory excitability were elevated in Df1/+ mice. PV+ interneurons, which are implicated in schizophrenia pathology, were reduced in density in the auditory cortex but not the secondary motor cortex. Both auditory brain abnormalities correlated with hearing impairment, which affected approximately 60% of adult Df1/+ mice and typically emerged before 6 weeks of age.

      Conclusions

      In the Df1/+ mouse model of 22q11.2 deletion syndrome, abnormalities in central auditory excitability and auditory cortical PV+ immunoreactivity correlate with hearing impairment. This is the first demonstration of cortical PV+ interneuron abnormalities correlating with hearing impairment in a mouse model of either schizophrenia or middle-ear inflammation.

      Keywords

      The multigene deletion that causes 22q11.2 deletion syndrome (22q11.2DS) is the strongest known cytogenetic risk factor for schizophrenia in humans (
      • McDonald-McGinn D.M.
      • Sullivan K.E.
      • Marino B.
      • Philip N.
      • Swillen A.
      • Vorstman J.A.S.
      • et al.
      22q11.2 deletion syndrome.
      ,
      • Paylor R.
      • Lindsay E.
      Mouse models of 22q11 deletion syndrome.
      ). Approximately 25% to 30% of patients with 22q11.2DS develop schizophrenia during adolescence or adulthood (
      • McDonald-McGinn D.M.
      • Sullivan K.E.
      • Marino B.
      • Philip N.
      • Swillen A.
      • Vorstman J.A.S.
      • et al.
      22q11.2 deletion syndrome.
      ,
      • Schneider M.
      • Debbané M.
      • Bassett A.S.
      • Chow E.W.C.
      • Fung W.L.A.
      • van den Bree M.
      • et al.
      Psychiatric disorders from childhood to adulthood in 22q11.2 deletion syndrome: Results from the International Consortium on Brain and Behavior in 22q11.2 Deletion Syndrome.
      ,
      • Drew L.J.
      • Crabtree G.W.
      • Markx S.
      • Stark K.L.
      • Chaverneff F.
      • Xu B.
      • et al.
      The 22q11.2 microdeletion: Fifteen years of insights into the genetic and neural complexity of psychiatric disorders.
      ). Up to 60% of patients with 22q11.2DS have hearing impairment (HI), arising primarily from high rates of recurrent or chronic otitis media (middle-ear inflammation) (
      • Verheij E.
      • Derks L.S.M.
      • Stegeman I.
      • Thomeer H.G.X.M.
      Prevalence of hearing loss and clinical otologic manifestations in patients with 22q11.2 deletion syndrome: A literature review.
      ).
      The Df1/+ mouse model of 22q11.2DS has an engineered hemizygous deletion of 1.2 Mbp encompassing 18 orthologs of genes deleted in human 22q11.2DS (
      • Lindsay E.A.
      • Botta A.
      • Jurecic V.
      • Carattini-Rivera S.
      • Cheah Y.C.
      • Rosenblatt H.M.
      • et al.
      Congenital heart disease in mice deficient for the DiGeorge syndrome region.
      ). Similar to other mouse models of 22q11.2DS, the Df1/+ mouse recapitulates many phenotypic features of the human syndrome (
      • Paylor R.
      • Lindsay E.
      Mouse models of 22q11 deletion syndrome.
      ,
      • Lindsay E.A.
      • Botta A.
      • Jurecic V.
      • Carattini-Rivera S.
      • Cheah Y.C.
      • Rosenblatt H.M.
      • et al.
      Congenital heart disease in mice deficient for the DiGeorge syndrome region.
      ,
      • Aggarwal V.S.
      • Liao J.
      • Bondarev A.
      • Schimmang T.
      • Lewandoski M.
      • Locker J.
      • et al.
      Dissection of Tbx1 and Fgf interactions in mouse models of 22q11DS suggests functional redundancy.
      ), including brain and behavioral anomalies that have been linked to schizophrenia in humans (
      • Hamm J.P.
      • Peterka D.S.
      • Gogos J.A.
      • Yuste R.
      Altered cortical ensembles in mouse models of schizophrenia.
      ,
      • Sigurdsson T.
      • Stark K.L.
      • Karayiorgou M.
      • Gogos J.A.
      • Gordon J.A.
      Impaired hippocampal-prefrontal synchrony in a genetic mouse model of schizophrenia.
      ). Df1/+ mice exhibit reduced prepulse inhibition of the acoustic startle response (
      • Paylor R.
      • McIlwain K.L.
      • McAninch R.
      • Nellis A.
      • Yuva-Paylor L.A.
      • Baldini A.
      • Lindsay E.A.
      Mice deleted for the DiGeorge/velocardiofacial syndrome region show abnormal sensorimotor gating and learning and memory impairments.
      ), an auditory behavioral marker for schizophrenia-like abnormalities and a common feature of 22q11.2DS in humans (
      • Drew L.J.
      • Crabtree G.W.
      • Markx S.
      • Stark K.L.
      • Chaverneff F.
      • Xu B.
      • et al.
      The 22q11.2 microdeletion: Fifteen years of insights into the genetic and neural complexity of psychiatric disorders.
      ). Specific abnormalities in auditory thalamocortical processing have also been reported in Df1/+ mice, including abnormal sensitivity of auditory thalamocortical projections to antipsychotic drugs (
      • Chun S.
      • Westmoreland J.J.
      • Bayazitov I.T.
      • Eddins D.
      • Pani A.K.
      • Smeyne R.J.
      • et al.
      Specific disruption of thalamic inputs to the auditory cortex in schizophrenia models.
      ). However, similar to humans with 22q11.2DS, up to 60% of Df1/+ mice have HI (
      • Fuchs J.C.
      • Zinnamon F.A.
      • Taylor R.R.
      • Ivins S.
      • Scambler P.J.
      • Forge A.
      • et al.
      Hearing loss in a mouse model of 22q11.2 deletion syndrome.
      ), which arises from developmental defects that increase susceptibility to otitis media (
      • Fuchs J.C.
      • Linden J.F.
      • Baldini A.
      • Tucker A.S.
      A defect in early myogenesis causes otitis media in two mouse models of 22q11.2 deletion syndrome.
      ). The potential interaction between HI and auditory brain abnormalities in Df1/+ mice has never been systematically explored.
      In humans, HI has been described as the “neglected risk factor for psychosis” (
      • Sommer I.E.
      • Roze C.M.
      • Linszen M.M.J.
      • Somers M.
      • van Zanten G.A.
      Hearing loss; the neglected risk factor for psychosis.
      ). Hearing loss is associated with increased risk of psychosis and hallucinations, and HI in childhood elevates the risk of developing schizophrenia later in life (
      • Linszen M.M.J.
      • Brouwer R.M.
      • Heringa S.M.
      • Sommer I.E.
      Increased risk of psychosis in patients with hearing impairment: Review and meta-analyses.
      ). The mechanisms underlying the association between HI and schizophrenia are unknown and could include common etiology, top-down influences (e.g., from social isolation), and/or bottom-up effects. A role for bottom-up effects is suggested by data from animal studies indicating that reductions in peripheral auditory input drive long-lasting changes in central auditory processing, which can affect behavior (
      • Chambers A.R.
      • Resnik J.
      • Yuan Y.
      • Whitton J.P.
      • Edge A.S.
      • Liberman M.C.
      • Polley D.B.
      Central gain restores auditory processing following near-complete cochlear denervation.
      ,
      • Sanes D.H.
      • Kotak V.C.
      Developmental plasticity of auditory cortical inhibitory synapses.
      ,
      • Takesian A.E.
      • Kotak V.C.
      • Sanes D.H.
      Developmental hearing loss disrupts synaptic inhibition: Implications for auditory processing.
      ,
      • Yao J.D.
      • Sanes D.H.
      Developmental deprivation-induced perceptual and cortical processing deficits in awake-behaving animals.
      ). Even moderate conductive HI, such as that caused by otitis media, can produce persistent changes in inhibitory synaptic transmission in the auditory cortex that persist after normal hearing is restored (
      • Sanes D.H.
      • Kotak V.C.
      Developmental plasticity of auditory cortical inhibitory synapses.
      ,
      • Takesian A.E.
      • Kotak V.C.
      • Sanes D.H.
      Developmental hearing loss disrupts synaptic inhibition: Implications for auditory processing.
      ,
      • Mowery T.M.
      • Kotak V.C.
      • Sanes D.H.
      Transient hearing loss within a critical period causes persistent changes to cellular properties in adult auditory cortex.
      ,
      • Takesian A.E.
      • Kotak V.C.
      • Sanes D.H.
      Age-dependent effect of hearing loss on cortical inhibitory synapse function.
      ).
      Here, we investigated the relationship between HI and auditory brain abnormalities in the Df1/+ mouse model of 22q11.2DS. We focused on neurophysiological and neuroanatomical markers associated with schizophrenia in humans, such as abnormalities in cortical auditory evoked potentials (AEPs) (
      • Bramon E.
      • Rabe-Hesketh S.
      • Sham P.
      • Murray R.M.
      • Frangou S.
      Meta-analysis of the P300 and P50 waveforms in schizophrenia.
      ) and parvalbumin-positive (PV+) cortical interneurons (
      • Lewis D.A.
      • Hashimoto T.
      • Volk D.W.
      Cortical inhibitory neurons and schizophrenia.
      ). PV+ interneurons play a key role in maintaining excitation-inhibition balance in the cortex (
      • Moore A.K.
      • Weible A.P.
      • Balmer T.S.
      • Trussell L.O.
      • Wehr M.
      Rapid rebalancing of excitation and inhibition by cortical circuitry.
      ), and abnormalities in these inhibitory cells are thought to be important to the pathophysiology of schizophrenia (
      • Lewis D.A.
      Inhibitory neurons in human cortical circuits: Substrate for cognitive dysfunction in schizophrenia.
      ). Our results reveal a significant correlation between HI in Df1/+ mice and both electrophysiological markers of central auditory excitability and reductions in density of PV-expressing cortical interneurons. Thus, interindividual differences in the magnitude of brain abnormalities in the Df1/+ mouse model of 22q11.2DS can be predicted from interindividual differences in the degree of peripheral HI.

      Methods and Materials

      Animals

      Df1/+ (also known as Df(16)1/+) mice (
      • Lindsay E.A.
      • Botta A.
      • Jurecic V.
      • Carattini-Rivera S.
      • Cheah Y.C.
      • Rosenblatt H.M.
      • et al.
      Congenital heart disease in mice deficient for the DiGeorge syndrome region.
      ) and their wild-type (WT) littermates were maintained in standard mouse housing facilities at either University College London or the National Institute of Mental Health. Experiments at University College London were performed in accordance with a Home Office project license approved under the United Kingdom Animal Scientific Procedures Act of 1986. Experiments at the National Institute of Mental Health were approved by the local Animal Care and Use Committee. See the Supplement for further details.

      Neurophysiology

      Auditory brainstem response (ABR) and cortical AEP recordings were obtained from mice anesthetized with ketamine and either medetomidine or dexmedetomidine. All testing was performed in a sound isolation booth. Auditory stimuli were presented either via an in-ear coupler (for longitudinal ABR threshold measurements) or free-field from a speaker directed at the ear under test. For ABR threshold measurements, we used click or tone stimuli presented at 0 to 90 dB sound pressure level (SPL). For comparisons of ABR and AEP wave magnitudes and latencies, we used 80-dB SPL click stimuli. ABR signals were recorded differentially between subdermal electrodes placed at the vertex (+) and behind or below the ear being tested (−), with a ground electrode either near the opposite ear (ABR threshold measurements) or over the olfactory bulb (ABR/AEP comparisons). AEP signals were recorded single-ended from subdermal electrodes placed over the temporal lobe contralateral to the ear being tested, relative to a ground over the olfactory bulb. See the Supplement for further details.

      Immunohistochemistry and Microscopy

      Coronal brain sections (50 μm thick) were either stained alternately for Nissl substance and PV or triple-stained for PV, NeuN, and DAPI. Sections stained for Nissl or DAPI were viewed at 2.5× to 5× magnifications to identify auditory cortex (A1) and secondary motor cortex (M2) with reference to a mouse brain atlas (
      • Paxinos G.
      • Franklin K.B.J.
      Paxinos and Franklin’s the Mouse Brain in Stereotaxic Coordinates.
      ). Single-plane images of A1 and M2 sections immunostained for PV and NeuN were then taken at 5× to 10× magnification with 720 pixels/inch resolution, using a Zeiss Axio Scan 2 Imaging microscope. See the Supplement for further details.

      Data Analysis

      ABRs and AEPs

      ABR signals were bandpass filtered in software (100–3000 Hz, 5th-order Butterworth) before averaging across trials; AEP signals were unfiltered aside from the 2.2- to 7500-Hz hardware filter used in data collection. The ABR threshold was identified as in previous work (
      • Fuchs J.C.
      • Zinnamon F.A.
      • Taylor R.R.
      • Ivins S.
      • Scambler P.J.
      • Forge A.
      • et al.
      Hearing loss in a mouse model of 22q11.2 deletion syndrome.
      ). ABR wave I amplitude was defined as the difference in signal amplitude between the moment of sound onset and the first peak of the ABR to an 80-dB SPL click. AEP P1-N1 and N1-P2 amplitudes were defined as amplitude differences between the respective AEP wave components (
      • Maxwell C.R.
      • Liang Y.
      • Weightman B.D.
      • Kanes S.J.
      • Abel T.
      • Gur R.E.
      • et al.
      Effects of chronic olanzapine and haloperidol differ on the mouse N1 auditory evoked potential.
      ): P1, maximum peak 15 to 30 ms after stimulus onset; N1, maximum negative deflection 25 to 60 ms after onset; and P2, maximum peak 60 to 110 ms after onset. Central auditory gain was defined as the amplitude of the AEP wave complex (P1-N1 or N1-P2) divided by the amplitude of ABR wave I.

      Cell Counts

      PV+ and NeuN+ cell counts and laminar distributions in A1 and M2 were estimated for images from both hemispheres in each mouse when possible. Immunohistochemical data from some hemispheres and animals were lost due to problems with perfusion, damage to sections, or aberrant fluorescence in images. See Table 1 for the numbers of mice and hemispheres used for comparisons shown in Results figures.
      Table 1Numbers of Mice and Brain Hemispheres Used for Analyses of PV+ and NeuN+ Cell Density and Laminar Distribution
      Cell TypeAreaSample UnitsAll WTAll Df1/+WT With ABRDf1/+ With ABR
      PV+A1Mice19191414 (6 NHI, 8 HI)
      Hemispheres32342224 (10 NHI, 14 HI)
      M2Mice25211916 (7 NHI, 9 HI)
      Hemispheres43363128 (11 NHI, 17 HI)
      NeuN+A1Mice710710 (4 NHI, 6 HI)
      Hemispheres10151015 (6 NHI, 9 HI)
      M2Mice14121412 (6 NHI, 6 HI)
      Hemispheres25202520 (10 NHI, 10 HI)
      All mice were included in comparisons of WT and Df1/+ mice (Figure 6B, E; Figure S2B, E and Figure S4A, C). Only data from mice that underwent ABR testing were included in comparisons of WT animals and Df1/+ mice with and without hearing impairment (Figure 6C, F; Figure S2C, F, Figure S3, and Figure S4B, D).
      A1, primary auditory cortex; ABR, auditory brainstem response; HI, hearing impairment; M2, secondary motor cortex; NHI, no hearing impairment; PV, parvalbumin; WT, wild-type.
      Cortical areas of interest were defined by overlaying the section image with the mouse atlas image (
      • Paxinos G.
      • Franklin K.B.J.
      Paxinos and Franklin’s the Mouse Brain in Stereotaxic Coordinates.
      ) for the corresponding coronal location using Adobe Photoshop Elements. Cell centers were marked and centroid coordinates recorded using ImageJ. For PV analysis, all immunolabeled cells in the cortical area of interest (A1 or M2) were counted. For NeuN analysis, immunolabeled cells were counted within a smaller pia-to-white matter rectangular strip through the center of the region of interest (5% of total area). Laminar distributions of cells were estimated using custom MATLAB software (The MathWorks, Inc.), which calculated cell centroid depth along a line perpendicular to the pial surface and white matter, normalized by the pia-to-white matter distance in each section. Laminar distributions were compared between animal groups using cell counts binned into 5 equal-depth bins by cortical depth; similar analyses were also performed using 10 or 20 bins in depth.

      Statistical Methods

      All data collection and analysis was conducted blinded to animal genotype, except in experiments involving longitudinal ABR measurement, which involved mostly Df1/+ mice. Separate measurements from the same animal obtained during auditory stimulation of left versus right ears were treated as independent measurements for some data analyses, because HI in Df1/+ mice frequently affected only one ear. The distribution of ABR thresholds for Df1/+ ears was bimodal rather than Gaussian (i.e., normal thresholds in some Df1/+ ears, significant HI in others). Therefore, for comparisons involving ABR threshold measurements (Figure 1, Figure 2, and 7; Figure S3), we used nonparametric tests (Wilcoxon rank-sum or signed-rank tests for differences in medians of two unpaired or paired samples; Spearman’s rank correlation tests). Distributions of evoked potential amplitudes and cell density were reasonably well approximated by Gaussian distributions. Therefore, for comparisons involving these measurements (Figure 4, Figure 5, Figure 6; Figures S1, S2, and S4), we used parametric tests (unpaired or paired t tests for differences in means of two unpaired or paired samples; ordinary one-way analysis of variance [ANOVA] for comparisons between multiple groups, followed by Fisher’s least significant difference [LSD] post hoc tests where group differences were significant). All statistical tests were two-tailed with α = 0.05.
      Figure thumbnail gr1
      Figure 1Elevated ABR thresholds in Df1/+ mice. (A) Click ABR thresholds recorded from individual ears in male and female WT (blue) and Df1/+ (red) mice. Data points represent individual ear measurements; animals typically contributed two measurements, one for each ear. p values indicate significant differences in Wilcoxon rank-sum tests (see text). Number of mice: 13 WT male, 13 WT female, 9 Df1/+ male, 16 Df1/+ female. (B) Click ABR thresholds pooled across recordings from male and female animals. Note that the Df1/+ ABR threshold distribution extends from the minimum to well beyond the maximum of the WT range. (C) Relationship between left and right ear ABR thresholds in each mouse. Slight horizontal scatter added to aid visualization of overlapping data points. Dashed lines indicate the upper bound of normal hearing, defined as 2.5 standard deviations above the mean ABR threshold for WT ears. Upper right quadrant, binaural HI; upper left and lower right quadrant, monaural HI; lower left quadrant, normal hearing. Overall, 60% (15 of 25) of Df1/+ mice had either monaural or binaural HI, and 46% (23 of 50) of Df1/+ ears exhibited HI. Monaural HI in Df1/+ mice occurred most commonly in the left ear, as observed previously (
      • Fuchs J.C.
      • Zinnamon F.A.
      • Taylor R.R.
      • Ivins S.
      • Scambler P.J.
      • Forge A.
      • et al.
      Hearing loss in a mouse model of 22q11.2 deletion syndrome.
      ). ABR, auditory brainstem response; F, female; HI, hearing impairment; L, left; M, male; R, right; SPL, sound pressure level; WT, wild-type.
      Figure thumbnail gr2
      Figure 2Hearing impairment typically emerges in a subset of Df1/+ mice before 6 weeks of age and persists into adulthood. (A) Click ABR thresholds recorded in individual ears of WT (blue) and Df1/+ (red) mice younger than 6 weeks old (i.e., before the typical age of sexual maturity). Data points represent individual ear ABR thresholds, averaged across any repeated measurements at ages younger than 6 weeks; each animal contributed two data points, one for each ear. Number of mice: 6 WT, 27 Df1/+. (B) Click ABR thresholds measured in the same mice at 3 to 6 weeks (<6 weeks) and 6 to 14 weeks (>6 weeks) of age. Individual ear threshold estimates were averaged across repeated measurements at different time points within either the <6 weeks age range (as in [A]) or the >6 weeks age range. Random vertical scatter (±3 dB SPL) added for display purposes only. p values indicate significant differences in Wilcoxon tests (see text). Number of mice: 4 WT, 7 Df1/+. (C) Maximum click-evoked ABR threshold across the two ears for each animal, shown for all measurement time points. Solid colored lines join repeated measurements from the same animal, where these could be obtained. Number of mice: 6 WT, 30 Df1/+. Random vertical scatter (±3 dB SPL) was added for display purposes only to help separate overlapping data points. ABR, auditory brainstem response; Max, maximum; SPL, sound pressure level; WT, wild-type.
      Figure thumbnail gr3
      Figure 3Average ABR and cortical AEP waveforms in WT and Df1/+ mice. (A) Example trial-averaged ABR to an 80-dB SPL click, recorded ipsilateral to the stimulated ear in an individual WT animal. Arrows indicate baseline and peak used for measurement of wave I amplitude. (B) Mean ABR waveforms averaged across recordings from WT mice (blue) and Df1/+ mice (red). Error bars indicate SEM across all trial-averaged ABR recordings for each group of animals. (C) Same as (B) but with Df1/+ ABR recordings separated into those from Df1/+ mice without HI (green, NHI) or Df1/+ mice with HI in at least one ear (magenta, HI). (D) Example trial-averaged AEP to an 80-dB SPL click, recorded over auditory cortex contralateral to the stimulated ear in a WT animal. Arrows indicate P1 peak, N1 trough, and P2 peak. (E) Mean AEP waveforms averaged across recordings from different mice; color conventions as in (B). Error bars indicate SEM across all trial-averaged AEP recordings for each group of animals. (F) Same as (E) but with Df1/+ AEP recordings separated into those from Df1/+ mice with or without HI in at least one ear; color conventions as in (C). Ipsilateral ABR and contralateral AEP data were obtained from the same recording for each stimulated ear; however ABR waveforms in (A–C) represent differential signals while AEP waveforms in (D–F) are single-ended signals (see ). Each animal typically contributed two data points, one for each ear/hemisphere combination. Number of mice: 20 WT, 20 Df1/+ (11 Df1/+ NHI, 9 Df1/+ HI). Number of ABR/AEP recordings: 39 WT, 40 Df1/+ (22 Df1/+ NHI, 18 Df1/+ HI). ABR, auditory brainstem response; AEP, auditory evoked potential; HI, hearing impairment; NHI, no hearing impairment; SPL, sound pressure level; WT, wild-type.
      Figure thumbnail gr4
      Figure 4Reductions in ABR wave I amplitude in Df1/+ mice with HI are not maintained in cortical AEPs. See text for details of statistical tests. (A) ABR wave I amplitude to an 80-dB SPL click does not differ between WT and Df1/+ mice overall. (B) However, wave I amplitude to an 80-dB SPL click is reduced in Df1/+ mice with HI relative to either WT mice or Df1/+ mice without HI, while there is no significant difference in ABR wave I amplitude between Df1/+ mice without HI and WT mice. (C, D) AEP P1-N1 amplitude does not differ between WT and Df1/+ mice, either overall (C) or when Df1/+ mice with and without HI are considered separately (D). (E, F) No significant differences in AEP N1-P2 amplitude between WT and Df1/+ mice, either overall (E) or when Df1/+ mice with and without HI are considered separately (F). Number of mice, number of ABR/AEP recordings, and color conventions as in . Bars and error bars indicate mean ± SEM across recordings. ABR, auditory brainstem response; AEP, auditory evoked potential; HI, hearing impairment; NHI, no hearing impairment; SPL, sound pressure level; WT, wild-type.
      Figure thumbnail gr5
      Figure 5Central auditory gain is elevated in Df1/+ mice with HI. See text for details of statistical tests. (A) The ratio of AEP P1-N1 amplitude to ABR wave I amplitude for an 80-dB SPL click does not differ between WT mice and Df1/+ mice overall. (B) However, this measure of central auditory gain for the P1-N1 complex is significantly elevated in Df1/+ mice with HI relative to either WT mice or Df1/+ mice without HI. (C) Same as (A) but for the ratio of AEP N1-P2 amplitude to ABR wave I amplitude; no difference between WT mice and Df1/+ mice overall. (D) Central auditory gain for the N1-P2 complex is significantly elevated in Df1/+ mice with HI relative to either WT mice or Df1/+ mice without HI. Number of mice and number of ABR/AEP recordings as in and ; plot conventions as in . ABR, auditory brainstem response; AEP, auditory evoked potential; HI, hearing impairment; NHI, no hearing impairment; SPL, sound pressure level; WT, wild-type.
      Figure thumbnail gr6
      Figure 6PV+ cell density is reduced in the auditory cortex but not the motor cortex of Df1/+ mice. (A) Example confocal image used for cell counting. Coronal section through A1 stained with an antibody against the inhibitory interneuron marker PV. Areas outside A1 are masked in black. Scale bar: 0.1 mm. (B) PV+ cell density in A1 was significantly reduced in Df1/+ mice overall compared with WT mice. (C) PV+ cell density in A1 was significantly reduced in Df1/+ mice with HI compared with either WT mice or Df1/+ mice without HI, but there was no significant difference between WT mice and Df1/+ mice without HI. (D) Example PV-immunostained coronal section used for cell counting in M2. Areas outside M2 are masked in black. Scale bar as in (A). (E) In M2, there was no significant difference in PV+ cell density between Df1/+ and WT mice overall. (F) PV+ cell density in M2 also did not differ between groups when comparing WT mice, Df1/+ mice without HI, and Df1/+ mice with HI. See text for details of statistical tests and for numbers of hemispheres (and mice) in each comparison. A1, primary auditory cortex; HI, hearing impairment; M2, secondary motor cortex; NHI, no hearing impairment; PV+, parvalbumin-positive; WT, wild-type.
      Figure thumbnail gr7
      Figure 7PV+ cell density in the auditory cortex correlates inversely with hearing impairment in Df1/+ mice. Each data point (blue, WT; red, Df1/+) represents a PV+ cell density measurement from A1 in the left or right hemisphere; individual mice typically contributed two measurements, one for each hemisphere. Here, hemisphere measurements are plotted against an overall measure of hearing impairment for each animal (x-axis), obtained by calculating the maximum click-evoked auditory brainstem response threshold across ears and then subtracting the mean of these values across WT animals only. For comparisons of PV+ cell density in each hemisphere to left, right, contralateral, and ipsilateral ear auditory brainstem response thresholds, see . Red text, Spearman’s rho and p value for correlation of PV+ cell density with hearing impairment for Df1/+ mice only. Solid red line, two-dimensional least squares linear fits to the Df1/+ data. Number of mice and number of hemispheres as in and . dB HL, decibels hearing loss relative to normal hearing threshold; PV+, parvalbumin-positive; WT, wild-type.

      Results

      Approximately 60% of Adult Df1/+ Mice Have HI in One or Both Ears

      We quantified hearing sensitivity in adult Df1/+ and WT mice aged 6.6 to 24.6 weeks (overall median = 10.1 weeks) using the click-evoked ABR as in previous work (
      • Fuchs J.C.
      • Zinnamon F.A.
      • Taylor R.R.
      • Ivins S.
      • Scambler P.J.
      • Forge A.
      • et al.
      Hearing loss in a mouse model of 22q11.2 deletion syndrome.
      ). There was no significant difference in age between the two groups (median [95% CI]: Df1/+, 8.3 [6.6–19.3] weeks; WT, 10.4 [6.6–24.6] weeks; Wilcoxon rank-sum test, p = .06). ABR thresholds were obtained for each ear in each mouse, except in one WT animal that died after measurement in only one ear.
      Replicating previous results obtained in a cohort of older Df1/+ and WT mice (
      • Fuchs J.C.
      • Zinnamon F.A.
      • Taylor R.R.
      • Ivins S.
      • Scambler P.J.
      • Forge A.
      • et al.
      Hearing loss in a mouse model of 22q11.2 deletion syndrome.
      ), we found clear evidence for HI in more than half of the Df1/+ animals (Figure 1). Median ABR thresholds were significantly higher in Df1/+ than WT mice (median [95% CI]: Df1/+, 40 [30–70] dB SPL; WT, 30 [30–40] dB SPL; Wilcoxon rank-sum test, p < .0001). Elevation of ABR thresholds in Df1/+ relative to WT mice was evident in both male and female animals, but there were no differences between genders within genotype (Wilcoxon rank-sum tests, p < .0001 between genotypes within gender, p > .1 between genders within genotype) (Figure 1A).
      There was substantial between-ear and interindividual variation in hearing ability among Df1/+ animals (Figure 1B), i.e., ABR thresholds were abnormally elevated in some Df1/+ ears but not others. Defining the upper bound of normal hearing as 2.5 SD above the mean ABR threshold for WT ears (i.e., abnormal hearing threshold: >40.88 dB SPL), we found that 46% (23 of 50) of Df1/+ ears and 0% (0 of 51) of WT ears displayed HI. Overall, 60% (15 of 25) of Df1/+ mice had either monaural or binaural HI, and monaural HI occurred most commonly in the left ear (Figure 1C). These results align both qualitatively and quantitatively with findings previously reported in Df1/+ and WT animals tested at similar or older ages (
      • Fuchs J.C.
      • Zinnamon F.A.
      • Taylor R.R.
      • Ivins S.
      • Scambler P.J.
      • Forge A.
      • et al.
      Hearing loss in a mouse model of 22q11.2 deletion syndrome.
      ).

      HI Emerges Before Adulthood in Df1/+ Mice

      To investigate the early timecourse of HI in Df1/+ mice, we measured click and tone ABR thresholds in mice as young as 3 weeks of age (i.e., at weaning) and conducted a longitudinal study of changes in ABR thresholds over time. This work was performed using a separate cohort of Df1/+ and WT mice bred and tested in a different facility and country (at the National Institutes of Health, United States, instead of University College London, United Kingdom).
      HI was evident in a subset of Df1/+ mice well before adulthood. Even among mice <6 weeks old, i.e., before puberty in mice (
      • Dutta S.
      • Sengupta P.
      Men and mice: Relating their ages.
      ), click ABR thresholds were elevated in Df1/+ ears compared with WT ears (median [95% CI]: Df1/+ 35 [30–45] dB SPL vs. WT 32.5 [30–37.2] dB SPL; Wilcoxon rank-sum test, p = .012) (Figure 2A). Moreover, early HI tended to persist in affected ears. In mice for which click ABR measurements could be obtained at both young and adult ages (<6 weeks and >6 weeks), we found significant differences in ear ABR thresholds between Df1/+ and WT animals within both age groups, but no significant differences between ages within genotype (Wilcoxon rank-sum tests, Df1/+ vs. WT: <6 weeks, p = .020; >6 weeks, p = .0027; Wilcoxon signed-rank tests, <6 vs. >6 weeks: Df1/+, p = .26; WT, p = 1) (Figure 2B).
      Thus, HI emerged early in a subset of Df1/+ animals and typically persisted for many weeks once it emerged. Longitudinal measurements of maximum ear click ABR thresholds for individual mice revealed multiple examples of Df1/+ mice with early-onset and persistent HI, along with examples of Df1/+ mice with normal hearing across all tested ages (Figure 2C). Similar results were also obtained when measuring ABR thresholds using 8 or 16 kHz tones.

      ABR Wave I Amplitude Reductions in Df1/+ Mice With HI Are Not Maintained in Cortical AEPs

      We wondered if auditory brain responses might differ between Df1/+ and WT mice and whether any differences might be related to the HI afflicting a subset of Df1/+ animals. Previous studies have reported abnormalities in sound-evoked auditory thalamic and/or cortical activity in mouse models of 22q11.2DS, but have either not investigated the role of HI (
      • Chun S.
      • Westmoreland J.J.
      • Bayazitov I.T.
      • Eddins D.
      • Pani A.K.
      • Smeyne R.J.
      • et al.
      Specific disruption of thalamic inputs to the auditory cortex in schizophrenia models.
      ) or not observed HI in the animals tested (
      • Didriksen M.
      • Fejgin K.
      • Nilsson S.R.O.
      • Birknow M.R.
      • Grayton H.M.
      • Larsen P.H.
      • et al.
      Persistent gating deficit and increased sensitivity to NMDA receptor antagonism after puberty in a new mouse model of the human 22q11.2 microdeletion syndrome: A study in male mice.
      ).
      We recorded both ABR waves and contralateral cortical AEP waves following presentations of loud suprathreshold (80 dB SPL) clicks at 300-ms interclick intervals in adult mice from the Figure 1 cohort. To assess the timing and strength of afferent input to the auditory brain, we measured the peak latency and baseline-to-peak amplitude of ABR wave I (Figure 3A), which arises from the auditory nerve. Within the AEP, we focused on wave peaks or troughs typically attributed to activity within the auditory thalamus (P1), auditory cortex (N1), and associative cortices (P2), measuring P1, N1, and P2 latency and P1-N1 and N1-P2 amplitudes (Figure 3D).
      HI, defined here as an elevation of the ABR threshold, would be expected to reduce ABR wave I amplitude for a suprathreshold click. Indeed, the amplitude of ABR wave I to an 80-dB SPL click was significantly lower in Df1/+ mice with HI than in either Df1/+ mice with no HI (NHI) or WT mice (one-way ANOVA, F2,76 = 5.55, group difference p = .0056; Fisher’s LSD, Df1/+ HI vs. WT p = .0094, Df1/+ HI vs. Df1/+ NHI p = .0019) (Figures 3C and 4B). However, there was no significant difference in ABR wave I amplitude between Df1/+ NHI mice and WT animals (unpaired t test, p = .33) (Figures 3C and 4B) nor between Df1/+ and WT mice overall (unpaired t test, p = .66) (Figures 3B and 4A).
      More surprisingly, there were no significant differences between Df1/+ and WT mice in either P1-N1 or N1-P2 cortical AEP wave amplitudes, even when Df1/+ mice with and without HI were considered separately (unpaired t test, WT vs. Df1/+ overall, P1-N1: p = .82 and N1-P2: p = .22; one-way ANOVA, WT vs. Df1/+ NHI vs. Df1/+ HI, group differences P1-N1: F2,76 = 0.025, p = .98 and N1-P2: F2,76 = 1.20, p = .31) (Figures 3E, F and 4C–F). There were also no significant differences in latencies of ABR wave I or cortical AEP waves P1, N1, or P2 between WT and Df1/+ animals, either overall or when HI in Df1/+ mice was taken into account (Figure S1).
      Thus, while ABR wave I amplitude was reduced as expected in Df1/+ mice with HI, there were no significant differences in the cortical AEP waves between any of the subgroups. This result suggests an increase in central auditory gain in Df1/+ mice with HI, as previously observed in animal models of more profound, bilateral hearing loss [e.g., (
      • Chambers A.R.
      • Resnik J.
      • Yuan Y.
      • Whitton J.P.
      • Edge A.S.
      • Liberman M.C.
      • Polley D.B.
      Central gain restores auditory processing following near-complete cochlear denervation.
      ,
      • Teichert M.
      • Liebmann L.
      • Hübner C.A.
      • Bolz J.
      Homeostatic plasticity and synaptic scaling in the adult mouse auditory cortex.
      )].

      Central Auditory Gain Is Elevated Specifically in Df1/+ Mice With HI

      To quantify central auditory gain, we compared ABR wave I amplitude to cortical AEP P1-N1 or N1-P2 amplitude recorded simultaneously over the contralateral cortical hemisphere. We used the ratios of cortical AEP P1-N1 or N1-P2 amplitude to ABR wave I amplitude as measures of central auditory gain.
      Both the P1-N1 and N1-P2 gain measures revealed elevated central auditory gain specifically in Df1/+ mice with HI (Figure 5). When comparing Df1/+ mice overall with WT mice, we observed no significant differences in the ratio of either AEP P1-N1 amplitude or N1-P2 amplitude to ABR wave I amplitude (unpaired t test, P1-N1: p = .36 and N1-P2: p = .084) (Figure 5A, C). However, the P1-N1 gain measure was significantly higher in Df1/+ mice with HI than in either WT mice or Df1/+ NHI mice, while Df1/+ NHI mice were not significantly different from WT animals (one-way ANOVA, F2,76 = 4.96, group difference p = .0094; Fisher’s LSD, Df1/+ HI vs. WT p = .011, Df1/+ HI vs. Df1/+ NHI p = .0037, WT vs. Df1/+ NHI p = .44) (Figure 5B). Similar results were obtained for the N1-P2 gain measure (one-way ANOVA, F2,76 = 7.68, group difference p = .0009; Fisher’s LSD, Df1/+ HI vs. WT p = .0006, Df1/+ HI vs. Df1/+ NHI p = .0009, WT vs. Df1/+ NHI p = .79) (Figure 5D). These results suggest that central auditory abnormalities arise in some Df1/+ mice as a consequence of HI.

      Df1/+ Mice With HI Have Reduced Density of PV+ Interneurons in the Auditory Cortex

      Changes in central auditory gain following HI have been linked with alterations in PV+ interneuron activity in the auditory cortex (
      • Resnik J.
      • Polley D.B.
      Cochlear neural degeneration disrupts hearing in background noise by increasing auditory cortex internal noise.
      ,
      • Resnik J.
      • Polley D.B.
      Fast-spiking GABA circuit dynamics in the auditory cortex predict recovery of sensory processing following peripheral nerve damage.
      ), and abnormalities in PV+ interneuron networks are also a common finding in animal models of schizophrenia [see (
      • Selten M.
      • van Bokhoven H.
      • Nadif Kasri N.
      Inhibitory control of the excitatory/inhibitory balance in psychiatric disorders.
      ,
      • Lewis D.A.
      • Curley A.A.
      • Glausier J.R.
      • Volk D.W.
      Cortical parvalbumin interneurons and cognitive dysfunction in schizophrenia.
      ) for reviews]. We wondered whether auditory cortical PV+ interneuron density might be abnormal in Df1/+ mice and, if so, how these abnormalities might relate to HI. To examine both PV+ cell density and density of neurons overall, we performed immunohistochemical staining for PV and NeuN (a pan-neuronal marker) in coronal brain sections through the auditory cortex (Figure 6A; Figure S2A) in adult Df1/+ and WT mice, most of which had also undergone ABR testing (Table 1).
      PV+ cell density in the auditory cortex was significantly lower in Df1/+ than WT mice (unpaired t test, p = .00030) (Figure 6B), and this difference arose primarily from abnormalities in the subset of Df1/+ mice with HI. In Df1/+ mice with HI, PV+ cell density was significantly lower than in either WT mice or Df1/+ NHI mice, while PV+ cell density in Df1/+ NHI mice did not differ from that in WT animals (one-way ANOVA, F2,43 = 6.37, group difference p = .0038; Fisher’s LSD, Df1/+ HI vs. WT p = .0011, Df1/+ HI vs. Df1/+ NHI p = .026, WT vs. Df1/+ NHI p = .53) (Figure 6C). In contrast, there were no significant differences in NeuN+ cell density in A1 between WT and Df1/+ animals with or without HI (Figure S2B, C).
      PV+ interneuron density in the auditory cortex was inversely correlated with the severity of HI in Df1/+ mice (Figure 7). We quantified the degree of HI in each mouse by calculating the maximum click-evoked ABR threshold across ears and then subtracting the average of these values across WT animals. In Df1/+ mice, auditory cortical PV+ cell density decreased as the degree of HI increased (Spearman’s ρ = −0.42, p = .0021) (Figure 7). Similar trends were evident when PV+ cell density in auditory cortical hemispheres from Df1/+ mice was compared with left, right, contralateral, or ipsilateral ear ABR thresholds, with a significant negative correlation for the relationship with left ear ABR threshold in particular (Figure S3). Thus, PV+ interneuron abnormalities in the auditory cortex of Df1/+ mice are related to the variable HI observed in these animals.

      Df1/+ Mice Do Not Show Abnormalities in PV+ or NeuN+ Cell Density in M2 or Changes in Laminar Distribution of PV+ Cells in A1

      The auditory cortex in mice is reciprocally connected with the secondary motor area (M2) in the frontal cortex, and neural activity in M2 is known to modulate auditory cortical processing (
      • Nelson A.
      • Schneider D.M.
      • Takatoh J.
      • Sakurai K.
      • Wang F.
      • Mooney R.
      A circuit for motor cortical modulation of auditory cortical activity.
      ,
      • Schneider D.M.
      • Nelson A.
      • Mooney R.
      A synaptic and circuit basis for corollary discharge in the auditory cortex.
      ). To find out if reductions in PV+ cell density observed in A1 of Df1/+ mice with HI also occurred in M2, we analyzed PV and NeuN immunostaining in coronal brain sections through the frontal cortex (Figure 6D; Figure S2D).
      Results suggest that reductions in PV+ cell density in Df1/+ mice with HI may be specific to the auditory cortex. PV+ cell density in M2 did not differ between WT and Df1/+ mice (unpaired t test, p = .46) (Figure 6E) or between WT mice, Df1/+ NHI mice, and Df1/+ mice with HI (one-way ANOVA, F2,56 = 1.04, group difference p = .36) (Figure 6F). There were also no significant differences between animal groups in NeuN+ cell density in M2 (Figure S2E, F).
      Furthermore, we observed no abnormalities in laminar distribution of PV+ interneurons in A1 of Df1/+ mice and minimal evidence for abnormalities in M2. Comparing WT mice with Df1/+ mice overall, we found no significant differences in the cortical depth distribution of PV+ interneurons in either A1 or M2 (Figure S4A, C). Comparing WT mice and Df1/+ mice with and without HI, we again found no significant differences in depth distribution of PV+ cells in A1, while a weak effect of HI was observed in M2 (Figure S4B, D). Post hoc tests identified the significant result in M2 as arising from a reduction in PV+ cell density in Df1/+ mice with HI at cortical depths 0.6 to 0.8 of the total distance from pia-to-white matter. This slight alteration in M2 PV+ cell distribution in Df1/+ mice with HI is reminiscent of aberrant laminar distributions of PV+ cells previously observed in medial cortical regions of the LgDel mouse (
      • Meechan D.W.
      • Tucker E.S.
      • Maynard T.M.
      • LaMantia A.S.
      Diminished dosage of 22q11 genes disrupts neurogenesis and cortical development in a mouse model of 22q11 deletion/DiGeorge syndrome.
      ,
      • Hunter K.P.
      • Willott J.F.
      Effects of bilateral lesions of auditory cortex in mice on the acoustic startle response.
      ). However, in M2 of Df1/+ mice, the laminar abnormalities appeared relatively weak, despite a comparatively large sample size.

      Discussion

      Our results show that abnormalities in cortical AEPs and PV+ interneuron density in the Df1/+ mouse model of 22q11.2DS are related to the degree of peripheral HI in individual Df1/+ animals. In principle, this correlation could arise from either direction of a causal relationship between auditory brain abnormalities and peripheral HI, or from a common underlying cause that varies across Df1/+ animals despite their genetic similarity.
      The most plausible of the two possible causal relationships is that auditory brain abnormalities in Df1/+ mice are caused either entirely by peripheral HI or by an interaction between HI and other genetic vulnerabilities associated with the 22q11.2 deletion. Peripheral HI in Df1/+ mice arises from middle-ear inflammation (otitis media) triggered by developmental defects in muscles of the Eustachian tube (
      • Fuchs J.C.
      • Zinnamon F.A.
      • Taylor R.R.
      • Ivins S.
      • Scambler P.J.
      • Forge A.
      • et al.
      Hearing loss in a mouse model of 22q11.2 deletion syndrome.
      ,
      • Fuchs J.C.
      • Linden J.F.
      • Baldini A.
      • Tucker A.S.
      A defect in early myogenesis causes otitis media in two mouse models of 22q11.2 deletion syndrome.
      ). It is highly unlikely that auditory cortical abnormalities in Df1/+ mice alter peripheral hearing sensitivity; even bilateral auditory cortex lesions do not affect ABR thresholds in mice (
      • Hunter K.P.
      • Willott J.F.
      Effects of bilateral lesions of auditory cortex in mice on the acoustic startle response.
      ). In contrast, experimentally induced peripheral HI is already known to increase central auditory gain and to alter cortical excitation/inhibition balance in mice and other animals (
      • Takesian A.E.
      • Kotak V.C.
      • Sanes D.H.
      Developmental hearing loss disrupts synaptic inhibition: Implications for auditory processing.
      ,
      • Resnik J.
      • Polley D.B.
      Cochlear neural degeneration disrupts hearing in background noise by increasing auditory cortex internal noise.
      ,
      • Kotak V.C.
      • Fujisawa S.
      • Lee F.A.
      • Karthikeyan O.
      • Aoki C.
      • Sanes D.H.
      Hearing loss raises excitability in the auditory cortex.
      ,
      • Kotak V.C.
      • Takesian A.E.
      • Sanes D.H.
      Hearing loss prevents the maturation of GABAergic transmission in the auditory cortex.
      ,
      • Persic D.
      • Thomas M.E.
      • Pelekanos V.
      • Ryugo D.K.
      • Takesian A.E.
      • Krumbholz K.
      • Pyott S.J.
      Regulation of auditory plasticity during critical periods and following hearing loss.
      ).
      It is also possible that individual differences in auditory brain abnormalities and peripheral HI among Df1/+ mice arise from a common underlying cause, such as varying levels of inflammation. Distinguishing the common-cause explanation from causal effects of HI will require further experiments in other mouse models of otitis media and in WT mice with induced HI.

      HI in Mouse Models of 22q11.2DS

      Our data confirm that approximately 60% of adult Df1/+ mice have HI in one or both ears (
      • Fuchs J.C.
      • Zinnamon F.A.
      • Taylor R.R.
      • Ivins S.
      • Scambler P.J.
      • Forge A.
      • et al.
      Hearing loss in a mouse model of 22q11.2 deletion syndrome.
      ) and demonstrate for the first time that HI emerges well before adulthood in affected animals. These observations raise the possibility of developmental as well as acute effects of HI on brain function in a subset of Df1/+ mice. Even HI that occurs only in one ear can drive plastic changes throughout the central auditory system, particularly if it occurs during development (
      • Sanes D.H.
      • Kotak V.C.
      Developmental plasticity of auditory cortical inhibitory synapses.
      ,
      • Mowery T.M.
      • Kotak V.C.
      • Sanes D.H.
      Transient hearing loss within a critical period causes persistent changes to cellular properties in adult auditory cortex.
      ,
      • Takesian A.E.
      • Kotak V.C.
      • Sanes D.H.
      Age-dependent effect of hearing loss on cortical inhibitory synapse function.
      ,
      • Popescu M.V.
      • Polley D.B.
      Monaural deprivation disrupts development of binaural selectivity in auditory midbrain and cortex.
      ,
      • Keating P.
      • Dahmen J.C.
      • King A.J.
      Complementary adaptive processes contribute to the developmental plasticity of spatial hearing.
      ).
      HI in Df1/+ mice has previously been shown to correlate ear-by-ear with otitis media (
      • Fuchs J.C.
      • Zinnamon F.A.
      • Taylor R.R.
      • Ivins S.
      • Scambler P.J.
      • Forge A.
      • et al.
      Hearing loss in a mouse model of 22q11.2 deletion syndrome.
      ), which is also the primary cause of HI in humans with 22q11.2DS (
      • Verheij E.
      • Derks L.S.M.
      • Stegeman I.
      • Thomeer H.G.X.M.
      Prevalence of hearing loss and clinical otologic manifestations in patients with 22q11.2 deletion syndrome: A literature review.
      ). In Df1/+ mice, susceptibility to otitis media arises from a developmental defect in a muscle affecting drainage of the middle ear through the Eustachian tube (
      • Fuchs J.C.
      • Linden J.F.
      • Baldini A.
      • Tucker A.S.
      A defect in early myogenesis causes otitis media in two mouse models of 22q11.2 deletion syndrome.
      ). This muscle defect is caused by haploinsufficiency of the gene Tbx1 (
      • Fuchs J.C.
      • Linden J.F.
      • Baldini A.
      • Tucker A.S.
      A defect in early myogenesis causes otitis media in two mouse models of 22q11.2 deletion syndrome.
      ,
      • Liao J.
      • Kochilas L.
      • Nowotschin S.
      • Arnold J.S.
      • Aggarwal V.S.
      • Epstein J.A.
      • et al.
      Full spectrum of malformations in velo-cardio-facial syndrome/DiGeorge syndrome mouse models by altering Tbx1 dosage.
      ); in humans, TBX1 lies within the minimum 22q11.2 deletion region. Thus, our results and previous work (
      • Fuchs J.C.
      • Zinnamon F.A.
      • Taylor R.R.
      • Ivins S.
      • Scambler P.J.
      • Forge A.
      • et al.
      Hearing loss in a mouse model of 22q11.2 deletion syndrome.
      ,
      • Fuchs J.C.
      • Linden J.F.
      • Baldini A.
      • Tucker A.S.
      A defect in early myogenesis causes otitis media in two mouse models of 22q11.2 deletion syndrome.
      ) suggest that any mouse model of 22q11.2DS with heterozygous deletion of Tbx1 may be susceptible to otitis media and HI from an early age.
      There are, however, some discrepant results in the literature; two previous studies that tested peripheral hearing sensitivity in mouse models of 22q11.2DS found no significant differences from WT animals (
      • Didriksen M.
      • Fejgin K.
      • Nilsson S.R.O.
      • Birknow M.R.
      • Grayton H.M.
      • Larsen P.H.
      • et al.
      Persistent gating deficit and increased sensitivity to NMDA receptor antagonism after puberty in a new mouse model of the human 22q11.2 microdeletion syndrome: A study in male mice.
      ,
      • Paylor R.
      • Glaser B.
      • Mupo A.
      • Ataliotis P.
      • Spencer C.
      • Sobotka A.
      • et al.
      Tbx1 haploinsufficiency is linked to behavioral disorders in mice and humans: Implications for 22q11 deletion syndrome.
      ). Age differences or genetic differences in the mice seem unlikely to explain the discrepant results, because HI is evident even in young Df1/+ mice and arises from Tbx1 haploinsufficiency. Differences in the microbiological status of the mice seem a more plausible explanation, given that opportunistic pathogens in laboratory mouse facilities can increase risk of otitis media (
      • Bleich A.
      • Kirsch P.
      • Sahly H.
      • Fahey J.
      • Smoczek A.
      • Hedrich H.J.
      • Sundberg J.P.
      Klebsiella oxytoca: Opportunistic infections in laboratory rodents.
      ). Mice used in this study were bred and maintained in standard mouse housing facilities. It is possible that the incidence of otitis media and HI in Df1/+ mice might be lower in superclean facilities. However, HI and otitis media have been found to affect a majority of human patients with 22q11.2DS (
      • Verheij E.
      • Derks L.S.M.
      • Stegeman I.
      • Thomeer H.G.X.M.
      Prevalence of hearing loss and clinical otologic manifestations in patients with 22q11.2 deletion syndrome: A literature review.
      ). Therefore, even if it were possible to reduce the incidence of otitis media in Df1/+ mice by restricting their microbiological exposure, the resulting animals would be poorer models of the human syndrome (
      • Willyard C.
      Squeaky clean mice could be ruining research.
      ).

      Central Auditory Abnormalities in Mouse Models of 22q11.2DS

      We found that measures of central auditory gain (e.g., ratios between AEP P1-N1 or N1-P2 amplitude and ABR wave I amplitude) were significantly higher in Df1/+ mice with HI than in WT mice or in Df1/+ NHI mice. This finding is consistent with previous literature on effects of HI. Loss of peripheral auditory input drives homeostatic changes throughout the auditory brainstem, midbrain, thalamus, and cortex, which typically manifest as reductions in inhibitory synaptic transmission, increased spontaneous activity, and increased gain of sound-evoked responses (
      • Chambers A.R.
      • Resnik J.
      • Yuan Y.
      • Whitton J.P.
      • Edge A.S.
      • Liberman M.C.
      • Polley D.B.
      Central gain restores auditory processing following near-complete cochlear denervation.
      ,
      • Takesian A.E.
      • Kotak V.C.
      • Sanes D.H.
      Developmental hearing loss disrupts synaptic inhibition: Implications for auditory processing.
      ,
      • Takesian A.E.
      • Kotak V.C.
      • Sanes D.H.
      Age-dependent effect of hearing loss on cortical inhibitory synapse function.
      ,
      • Resnik J.
      • Polley D.B.
      Cochlear neural degeneration disrupts hearing in background noise by increasing auditory cortex internal noise.
      ,
      • Eggermont J.J.
      Acquired hearing loss and brain plasticity.
      ,
      • Clarkson C.
      • Antunes F.M.
      • Rubio M.E.
      Conductive hearing loss has long-lasting structural and molecular effects on presynaptic and postsynaptic structures of auditory nerve synapses in the cochlear nucleus.
      ,
      • Sinclair J.L.
      • Fischl M.J.
      • Alexandrova O.
      • Heβ M.
      • Grothe B.
      • Leibold C.
      • Kopp-Scheinpflug C.
      Sound-evoked activity influences myelination of brainstem axons in the trapezoid body.
      ,
      • Xu H.
      • Kotak V.C.
      • Sanes D.H.
      Conductive hearing loss disrupts synaptic and spike adaptation in developing auditory cortex.
      ). Thus, increased central auditory gain in Df1/+ mice with HI could arise at multiple stages of the central auditory pathway.

      PV+ Cortical Interneurons and HI

      We observed a reduction in the density of PV-expressing cortical interneurons in Df1/+ mice, which was specific to the auditory cortex and correlated with degree of HI in individual animals.
      To our knowledge, this is not only the first report of a link between HI and reduced PV+ interneuron density in an animal model of schizophrenia but also the first indication that HI due to otitis media may influence PV+ interneuron density in the auditory cortex. Previous studies in mice have demonstrated that PV+ interneuron density and distribution in the auditory cortex can be affected by age-related changes in the auditory system (
      • Martin del Campo H.N.
      • Measor K.R.
      • Razak K.A.
      Parvalbumin immunoreactivity in the auditory cortex of a mouse model of presbycusis.
      ,
      • Brewton D.H.
      • Kokash J.
      • Jimenez O.
      • Pena E.R.
      • Razak K.A.
      Age-related deterioration of perineuronal nets in the primary auditory cortex of mice.
      ,
      • Nguyen A.
      • Khaleel H.M.
      • Razak K.A.
      Effects of noise-induced hearing loss on parvalbumin and perineuronal net expression in the mouse primary auditory cortex.
      ,
      • Rogalla M.M.
      • Hildebrandt K.J.
      Aging but not age-related hearing loss dominates the decrease of parvalbumin immunoreactivity in the primary auditory cortex of mice.
      ), by noise-induced or pharmacologically induced sensorineural hearing loss (
      • Resnik J.
      • Polley D.B.
      Fast-spiking GABA circuit dynamics in the auditory cortex predict recovery of sensory processing following peripheral nerve damage.
      ,
      • Nguyen A.
      • Khaleel H.M.
      • Razak K.A.
      Effects of noise-induced hearing loss on parvalbumin and perineuronal net expression in the mouse primary auditory cortex.
      ), and by mutations that disrupt both auditory hair cell function and cortical interneuron migration (
      • Libé-Philippot B.
      • Michel V.
      • Boutet de Monvel J.
      • Le Gal S.
      • Dupont T.
      • Avan P.
      • et al.
      Auditory cortex interneuron development requires cadherins operating hair-cell mechanoelectrical transduction.
      ). Our findings raise the additional possibility that conductive HI, either alone or in combination with genetic risk factors for schizophrenia, may lead to reductions in PV+ interneuron density.
      Reduced PV+ cell density could arise from disrupted PV+ cell migration to cortex during embryonic development (embryonic days 13–17), increased PV+ cell death during postnatal development (postnatal days 5–15), and/or reduction in PV expression in cortical interneurons after development (
      • Meechan D.W.
      • Rutz H.L.H.
      • Fralish M.S.
      • Maynard T.M.
      • Rothblat L.A.
      • LaMantia A.S.
      Cognitive ability is associated with altered medial frontal cortical circuits in the LgDel mouse model of 22q11.2DS.
      ,
      • Al-Absi A.R.
      • Qvist P.
      • Okujeni S.
      • Khan A.R.
      • Glerup S.
      • Sanchez C.
      • Nyengaard J.R.
      Layers II/III of prefrontal cortex in Df(h22q11)/+ mouse model of the 22q11.2 deletion display loss of parvalbumin interneurons and modulation of neuronal morphology and excitability.
      ). Previous work suggests that otitis media develops soon after ear opening (at postnatal day 11) in affected Df1/+ ears (
      • Fuchs J.C.
      • Linden J.F.
      • Baldini A.
      • Tucker A.S.
      A defect in early myogenesis causes otitis media in two mouse models of 22q11.2 deletion syndrome.
      ), a finding consistent with our observation of HI in Df1/+ mice at 3 to 6 weeks of age. Therefore, HI in Df1/+ mice likely emerges after embryonic migration of PV+ cells but might affect postnatal PV+ cell development and PV expression in adulthood. Further experiments are required to determine the timing of the reduction in PV+ cell density in the auditory cortex.

      PV+ Cortical Interneurons in Mouse Models of 22q11.2DS

      PV+ interneurons are known to play a pivotal role in maintenance of normal cortical circuit function (
      • Sohal V.S.
      • Zhang F.
      • Yizhar O.
      • Deisseroth K.
      Parvalbumin neurons and gamma rhythms enhance cortical circuit performance.
      ,
      • Gothner T.
      • Gonçalves P.J.
      • Sahani M.
      • Linden J.F.
      • Hildebrandt K.J.
      Sustained activation of PV+ interneurons in core auditory cortex enables robust divisive gain control for complex and naturalistic stimuli.
      ,
      • Cardin J.A.
      • Carlén M.
      • Meletis K.
      • Knoblich U.
      • Zhang F.
      • Deisseroth K.
      • et al.
      Driving fast-spiking cells induces gamma rhythm and controls sensory responses.
      ). Previous studies of mouse models of 22q11.2DS have reported altered laminar distribution and/or reduced density of PV+ interneurons in the medial prefrontal cortex and hippocampus (
      • Meechan D.W.
      • Tucker E.S.
      • Maynard T.M.
      • LaMantia A.S.
      Diminished dosage of 22q11 genes disrupts neurogenesis and cortical development in a mouse model of 22q11 deletion/DiGeorge syndrome.
      ,
      • Meechan D.W.
      • Rutz H.L.H.
      • Fralish M.S.
      • Maynard T.M.
      • Rothblat L.A.
      • LaMantia A.S.
      Cognitive ability is associated with altered medial frontal cortical circuits in the LgDel mouse model of 22q11.2DS.
      ,
      • Al-Absi A.R.
      • Qvist P.
      • Okujeni S.
      • Khan A.R.
      • Glerup S.
      • Sanchez C.
      • Nyengaard J.R.
      Layers II/III of prefrontal cortex in Df(h22q11)/+ mouse model of the 22q11.2 deletion display loss of parvalbumin interneurons and modulation of neuronal morphology and excitability.
      ,
      • Toritsuka M.
      • Kimoto S.
      • Muraki K.
      • Landek-Salgado M.A.
      • Yoshida A.
      • Yamamoto N.
      • et al.
      Deficits in microRNA-mediated Cxcr4/Cxcl12 signaling in neurodevelopmental deficits in a 22q11 deletion syndrome mouse model.
      ,
      • Piskorowski R.A.
      • Nasrallah K.
      • Diamantopoulou A.
      • Mukai J.
      • Hassan S.I.
      • Siegelbaum S.A.
      • et al.
      Age-dependent specific changes in area CA2 of the hippocampus and social memory deficit in a mouse model of the 22q11.2 deletion syndrome.
      ). Abnormalities in PV+ interneurons are also a common finding in human schizophrenia and are thought to contribute to cognitive deficits (
      • Lewis D.A.
      Inhibitory neurons in human cortical circuits: Substrate for cognitive dysfunction in schizophrenia.
      ,
      • Beasley C.L.
      • Zhang Z.J.
      • Patten I.
      • Reynolds G.P.
      Selective deficits in prefrontal cortical GABAergic neurons in schizophrenia defined by the presence of calcium-binding proteins.
      ,
      • Hashimoto T.
      • Volk D.W.
      • Eggan S.M.
      • Mirnics K.
      • Pierri J.N.
      • Sun Z.
      • et al.
      Gene expression deficits in a subclass of GABA neurons in the prefrontal cortex of subjects with schizophrenia.
      ,
      • Uhlhaas P.J.
      • Singer W.
      Abnormal neural oscillations and synchrony in schizophrenia.
      ,
      • Dienel S.J.
      • Lewis D.A.
      Alterations in cortical interneurons and cognitive function in schizophrenia.
      ). Thus, auditory cortical PV+ interneuron abnormalities in mouse models of 22q11.2DS seem likely to be relevant to understanding cortical circuit dysfunction in schizophrenia and the influence of other potential risk factors, such as HI.

      Implications for Schizophrenia Research

      In humans, there is compelling evidence that HI increases the risk of psychosis and hallucinations [see (
      • Linszen M.M.J.
      • Brouwer R.M.
      • Heringa S.M.
      • Sommer I.E.
      Increased risk of psychosis in patients with hearing impairment: Review and meta-analyses.
      ) for a recent meta-analysis and review]. Moreover, HI and/or middle-ear disease in childhood is associated with elevated risk of developing schizophrenia in adulthood (
      • Linszen M.M.J.
      • Brouwer R.M.
      • Heringa S.M.
      • Sommer I.E.
      Increased risk of psychosis in patients with hearing impairment: Review and meta-analyses.
      ,
      • David A.
      • Malmberg A.
      • Lewis G.
      • Brandt L.
      • Allebeck P.
      Are there neurological and sensory risk factors for schizophrenia?.
      ,
      • Fors A.
      • Abel K.M.
      • Wicks S.
      • Magnusson C.
      • Dalman C.
      Hearing and speech impairment at age 4 and risk of later non-affective psychosis.
      ,
      • Mason P.
      • Rimmer M.
      • Richman A.
      • Garg G.
      • Johnson J.
      • Mottram P.G.
      Middle-ear disease and schizophrenia: Case-control study.
      ). The mechanisms underlying this association are unknown but could include changes in neuronal networks driven by loss of sensory input. In individuals with genetic vulnerability to schizophrenia, including but not only patients with 22q11.2DS, HI from middle-ear problems might be a critical second hit that breaks the balance of excitation and inhibition in the cortex and promotes development of hallucinations and other schizophrenia symptoms. Our results demonstrate that the Df1/+ mouse model of 22q11.2DS is an ideal system for studying how genetic vulnerability to schizophrenia, HI, and/or interactions between these factors could produce brain abnormalities that promote psychiatric disease.

      Acknowledgments and Disclosures

      This work was supported by the National Institute of Mental Health (NIMH) Division of Intramural Research Program (Grant No. ZIA MH002897 [to KHW, QL, and FAZ]), the University College London–NIMH Graduate Partnerships Program (to FAZ), the Del Monte Institute for Neuroscience at the University of Rochester Medical Center (to KHW), the UK Research and Innovation Medical Research Council (Grant No. MR/P006221/1 [to JFL]), and Action on Hearing Loss (Grant No. G77 [to JFL]).
      We thank Drs. T. Fitzgerald and T. Wafa for assisting FAZ in conducting the auditory testing procedures at the Mouse Auditory Testing Core Facility at the National Institute on Deafness and Other Communication Disorders and Drs. A. Meyer and S. Mastwal for critical reading and discussion of early manuscript drafts.
      A previous version of this article was published as a preprint on bioRxiv: https://www.biorxiv.org/content/10.1101/539650v1 (
      • Zinnamon F.A.
      • Harrison F.G.
      • Wenas S.S.
      • Meyer A.F.
      • Liu Q.
      • Wang K.H.
      • et al.
      Hearing loss promotes schizophrenia-relevant brain and behavioral abnormalities in a mouse model of human 22q11.2 Deletion Syndrome.
      ).
      The authors report no biomedical financial interests or potential conflicts of interest.

      References

        • McDonald-McGinn D.M.
        • Sullivan K.E.
        • Marino B.
        • Philip N.
        • Swillen A.
        • Vorstman J.A.S.
        • et al.
        22q11.2 deletion syndrome.
        Nat Rev Dis Primers. 2015; 1: 15071
        • Paylor R.
        • Lindsay E.
        Mouse models of 22q11 deletion syndrome.
        Biol Psychiatry. 2006; 59: 1172-1179
        • Schneider M.
        • Debbané M.
        • Bassett A.S.
        • Chow E.W.C.
        • Fung W.L.A.
        • van den Bree M.
        • et al.
        Psychiatric disorders from childhood to adulthood in 22q11.2 deletion syndrome: Results from the International Consortium on Brain and Behavior in 22q11.2 Deletion Syndrome.
        Am J Psychiatry. 2014; 171: 627-639
        • Drew L.J.
        • Crabtree G.W.
        • Markx S.
        • Stark K.L.
        • Chaverneff F.
        • Xu B.
        • et al.
        The 22q11.2 microdeletion: Fifteen years of insights into the genetic and neural complexity of psychiatric disorders.
        Int J Dev Neurosci. 2011; 29: 259-281
        • Verheij E.
        • Derks L.S.M.
        • Stegeman I.
        • Thomeer H.G.X.M.
        Prevalence of hearing loss and clinical otologic manifestations in patients with 22q11.2 deletion syndrome: A literature review.
        Clin Otolaryngol. 2017; 42: 1319-1328
        • Lindsay E.A.
        • Botta A.
        • Jurecic V.
        • Carattini-Rivera S.
        • Cheah Y.C.
        • Rosenblatt H.M.
        • et al.
        Congenital heart disease in mice deficient for the DiGeorge syndrome region.
        Nature. 1999; 401: 379-383
        • Aggarwal V.S.
        • Liao J.
        • Bondarev A.
        • Schimmang T.
        • Lewandoski M.
        • Locker J.
        • et al.
        Dissection of Tbx1 and Fgf interactions in mouse models of 22q11DS suggests functional redundancy.
        Hum Mol Genet. 2006; 15: 3219-3228
        • Hamm J.P.
        • Peterka D.S.
        • Gogos J.A.
        • Yuste R.
        Altered cortical ensembles in mouse models of schizophrenia.
        Neuron. 2017; 94: 153-167.e8
        • Sigurdsson T.
        • Stark K.L.
        • Karayiorgou M.
        • Gogos J.A.
        • Gordon J.A.
        Impaired hippocampal-prefrontal synchrony in a genetic mouse model of schizophrenia.
        Nature. 2010; 464: 763-767
        • Paylor R.
        • McIlwain K.L.
        • McAninch R.
        • Nellis A.
        • Yuva-Paylor L.A.
        • Baldini A.
        • Lindsay E.A.
        Mice deleted for the DiGeorge/velocardiofacial syndrome region show abnormal sensorimotor gating and learning and memory impairments.
        Hum Mol Genet. 2001; 10: 2645-2650
        • Chun S.
        • Westmoreland J.J.
        • Bayazitov I.T.
        • Eddins D.
        • Pani A.K.
        • Smeyne R.J.
        • et al.
        Specific disruption of thalamic inputs to the auditory cortex in schizophrenia models.
        Science. 2014; 344: 1178-1182
        • Fuchs J.C.
        • Zinnamon F.A.
        • Taylor R.R.
        • Ivins S.
        • Scambler P.J.
        • Forge A.
        • et al.
        Hearing loss in a mouse model of 22q11.2 deletion syndrome.
        PLoS One. 2013; 8e80104
        • Fuchs J.C.
        • Linden J.F.
        • Baldini A.
        • Tucker A.S.
        A defect in early myogenesis causes otitis media in two mouse models of 22q11.2 deletion syndrome.
        Hum Mol Genet. 2015; 24: 1869-1882
        • Sommer I.E.
        • Roze C.M.
        • Linszen M.M.J.
        • Somers M.
        • van Zanten G.A.
        Hearing loss; the neglected risk factor for psychosis.
        Schizophr Res. 2014; 158: 266-267
        • Linszen M.M.J.
        • Brouwer R.M.
        • Heringa S.M.
        • Sommer I.E.
        Increased risk of psychosis in patients with hearing impairment: Review and meta-analyses.
        Neurosci Biobehav Rev. 2016; 62: 1-20
        • Chambers A.R.
        • Resnik J.
        • Yuan Y.
        • Whitton J.P.
        • Edge A.S.
        • Liberman M.C.
        • Polley D.B.
        Central gain restores auditory processing following near-complete cochlear denervation.
        Neuron. 2016; 89: 867-879
        • Sanes D.H.
        • Kotak V.C.
        Developmental plasticity of auditory cortical inhibitory synapses.
        Hear Res. 2011; 279: 140-148
        • Takesian A.E.
        • Kotak V.C.
        • Sanes D.H.
        Developmental hearing loss disrupts synaptic inhibition: Implications for auditory processing.
        Future Neurol. 2009; 4: 331-349
        • Yao J.D.
        • Sanes D.H.
        Developmental deprivation-induced perceptual and cortical processing deficits in awake-behaving animals.
        Elife. 2018; 7e33891
        • Mowery T.M.
        • Kotak V.C.
        • Sanes D.H.
        Transient hearing loss within a critical period causes persistent changes to cellular properties in adult auditory cortex.
        Cereb Cortex. 2015; 25: 2083-2094
        • Takesian A.E.
        • Kotak V.C.
        • Sanes D.H.
        Age-dependent effect of hearing loss on cortical inhibitory synapse function.
        J Neurophysiol. 2012; 107: 937-947
        • Bramon E.
        • Rabe-Hesketh S.
        • Sham P.
        • Murray R.M.
        • Frangou S.
        Meta-analysis of the P300 and P50 waveforms in schizophrenia.
        Schizophr Res. 2004; 70: 315-329
        • Lewis D.A.
        • Hashimoto T.
        • Volk D.W.
        Cortical inhibitory neurons and schizophrenia.
        Nat Rev Neurosci. 2005; 6: 312-324
        • Moore A.K.
        • Weible A.P.
        • Balmer T.S.
        • Trussell L.O.
        • Wehr M.
        Rapid rebalancing of excitation and inhibition by cortical circuitry.
        Neuron. 2018; 97: 1341-1355.e6
        • Lewis D.A.
        Inhibitory neurons in human cortical circuits: Substrate for cognitive dysfunction in schizophrenia.
        Curr Opin Neurobiol. 2014; 26: 22-26
        • Paxinos G.
        • Franklin K.B.J.
        Paxinos and Franklin’s the Mouse Brain in Stereotaxic Coordinates.
        4th ed. Academic Press, Cambridge, MA2012
        • Maxwell C.R.
        • Liang Y.
        • Weightman B.D.
        • Kanes S.J.
        • Abel T.
        • Gur R.E.
        • et al.
        Effects of chronic olanzapine and haloperidol differ on the mouse N1 auditory evoked potential.
        Neuropsychopharmacology. 2004; 29: 739-746
        • Dutta S.
        • Sengupta P.
        Men and mice: Relating their ages.
        Life Sci. 2016; 152: 244-248
        • Didriksen M.
        • Fejgin K.
        • Nilsson S.R.O.
        • Birknow M.R.
        • Grayton H.M.
        • Larsen P.H.
        • et al.
        Persistent gating deficit and increased sensitivity to NMDA receptor antagonism after puberty in a new mouse model of the human 22q11.2 microdeletion syndrome: A study in male mice.
        J Psychiatry Neurosci. 2017; 42: 48-58
        • Teichert M.
        • Liebmann L.
        • Hübner C.A.
        • Bolz J.
        Homeostatic plasticity and synaptic scaling in the adult mouse auditory cortex.
        Sci Rep. 2017; 7: 17423
        • Resnik J.
        • Polley D.B.
        Cochlear neural degeneration disrupts hearing in background noise by increasing auditory cortex internal noise.
        Neuron. 2021; 109: 984-996.e4
        • Resnik J.
        • Polley D.B.
        Fast-spiking GABA circuit dynamics in the auditory cortex predict recovery of sensory processing following peripheral nerve damage.
        Elife. 2017; 6e21452
        • Selten M.
        • van Bokhoven H.
        • Nadif Kasri N.
        Inhibitory control of the excitatory/inhibitory balance in psychiatric disorders.
        F1000Res. 2018; 7: 23
        • Lewis D.A.
        • Curley A.A.
        • Glausier J.R.
        • Volk D.W.
        Cortical parvalbumin interneurons and cognitive dysfunction in schizophrenia.
        Trends Neurosci. 2012; 35: 57-67
        • Nelson A.
        • Schneider D.M.
        • Takatoh J.
        • Sakurai K.
        • Wang F.
        • Mooney R.
        A circuit for motor cortical modulation of auditory cortical activity.
        J Neurosci. 2013; 33: 14342-14353
        • Schneider D.M.
        • Nelson A.
        • Mooney R.
        A synaptic and circuit basis for corollary discharge in the auditory cortex.
        Nature. 2014; 513: 189-194
        • Meechan D.W.
        • Tucker E.S.
        • Maynard T.M.
        • LaMantia A.S.
        Diminished dosage of 22q11 genes disrupts neurogenesis and cortical development in a mouse model of 22q11 deletion/DiGeorge syndrome.
        Proc Natl Acad Sci U S A. 2009; 106: 16434-16445
        • Hunter K.P.
        • Willott J.F.
        Effects of bilateral lesions of auditory cortex in mice on the acoustic startle response.
        Physiol Behav. 1993; 54: 1133-1139
        • Kotak V.C.
        • Fujisawa S.
        • Lee F.A.
        • Karthikeyan O.
        • Aoki C.
        • Sanes D.H.
        Hearing loss raises excitability in the auditory cortex.
        J Neurosci. 2005; 25: 3908-3918
        • Kotak V.C.
        • Takesian A.E.
        • Sanes D.H.
        Hearing loss prevents the maturation of GABAergic transmission in the auditory cortex.
        Cereb Cortex. 2008; 18: 2098-2108
        • Persic D.
        • Thomas M.E.
        • Pelekanos V.
        • Ryugo D.K.
        • Takesian A.E.
        • Krumbholz K.
        • Pyott S.J.
        Regulation of auditory plasticity during critical periods and following hearing loss.
        Hear Res. 2020; 397: 107976
        • Popescu M.V.
        • Polley D.B.
        Monaural deprivation disrupts development of binaural selectivity in auditory midbrain and cortex.
        Neuron. 2010; 65: 718-731
        • Keating P.
        • Dahmen J.C.
        • King A.J.
        Complementary adaptive processes contribute to the developmental plasticity of spatial hearing.
        Nat Neurosci. 2015; 18: 185-187
        • Liao J.
        • Kochilas L.
        • Nowotschin S.
        • Arnold J.S.
        • Aggarwal V.S.
        • Epstein J.A.
        • et al.
        Full spectrum of malformations in velo-cardio-facial syndrome/DiGeorge syndrome mouse models by altering Tbx1 dosage.
        Hum Mol Genet. 2004; 13: 1577-1585
        • Paylor R.
        • Glaser B.
        • Mupo A.
        • Ataliotis P.
        • Spencer C.
        • Sobotka A.
        • et al.
        Tbx1 haploinsufficiency is linked to behavioral disorders in mice and humans: Implications for 22q11 deletion syndrome.
        Proc Natl Acad Sci U S A. 2006; 103: 7729-7734
        • Bleich A.
        • Kirsch P.
        • Sahly H.
        • Fahey J.
        • Smoczek A.
        • Hedrich H.J.
        • Sundberg J.P.
        Klebsiella oxytoca: Opportunistic infections in laboratory rodents.
        Lab Anim. 2008; 42: 369-375
        • Willyard C.
        Squeaky clean mice could be ruining research.
        Nature. 2018; 556: 16-18
        • Eggermont J.J.
        Acquired hearing loss and brain plasticity.
        Hear Res. 2017; 343: 176-190
        • Clarkson C.
        • Antunes F.M.
        • Rubio M.E.
        Conductive hearing loss has long-lasting structural and molecular effects on presynaptic and postsynaptic structures of auditory nerve synapses in the cochlear nucleus.
        J Neurosci. 2016; 36: 10214-10227
        • Sinclair J.L.
        • Fischl M.J.
        • Alexandrova O.
        • Heβ M.
        • Grothe B.
        • Leibold C.
        • Kopp-Scheinpflug C.
        Sound-evoked activity influences myelination of brainstem axons in the trapezoid body.
        J Neurosci. 2017; 37: 8239-8255
        • Xu H.
        • Kotak V.C.
        • Sanes D.H.
        Conductive hearing loss disrupts synaptic and spike adaptation in developing auditory cortex.
        J Neurosci. 2007; 27: 9417-9426
        • Martin del Campo H.N.
        • Measor K.R.
        • Razak K.A.
        Parvalbumin immunoreactivity in the auditory cortex of a mouse model of presbycusis.
        Hear Res. 2012; 294: 31-39
        • Brewton D.H.
        • Kokash J.
        • Jimenez O.
        • Pena E.R.
        • Razak K.A.
        Age-related deterioration of perineuronal nets in the primary auditory cortex of mice.
        Front Aging Neurosci. 2016; 8: 270
        • Nguyen A.
        • Khaleel H.M.
        • Razak K.A.
        Effects of noise-induced hearing loss on parvalbumin and perineuronal net expression in the mouse primary auditory cortex.
        Hear Res. 2017; 350: 82-90
        • Rogalla M.M.
        • Hildebrandt K.J.
        Aging but not age-related hearing loss dominates the decrease of parvalbumin immunoreactivity in the primary auditory cortex of mice.
        eNeuro. 2020; 7 (ENEURO.0511-19.2020)
        • Libé-Philippot B.
        • Michel V.
        • Boutet de Monvel J.
        • Le Gal S.
        • Dupont T.
        • Avan P.
        • et al.
        Auditory cortex interneuron development requires cadherins operating hair-cell mechanoelectrical transduction.
        Proc Natl Acad Sci U S A. 2017; 114: 7765-7774
        • Meechan D.W.
        • Rutz H.L.H.
        • Fralish M.S.
        • Maynard T.M.
        • Rothblat L.A.
        • LaMantia A.S.
        Cognitive ability is associated with altered medial frontal cortical circuits in the LgDel mouse model of 22q11.2DS.
        Cereb Cortex. 2015; 25: 1143-1151
        • Al-Absi A.R.
        • Qvist P.
        • Okujeni S.
        • Khan A.R.
        • Glerup S.
        • Sanchez C.
        • Nyengaard J.R.
        Layers II/III of prefrontal cortex in Df(h22q11)/+ mouse model of the 22q11.2 deletion display loss of parvalbumin interneurons and modulation of neuronal morphology and excitability.
        Mol Neurobiol. 2020; 57: 4978-4988
        • Sohal V.S.
        • Zhang F.
        • Yizhar O.
        • Deisseroth K.
        Parvalbumin neurons and gamma rhythms enhance cortical circuit performance.
        Nature. 2009; 459: 698-702
        • Gothner T.
        • Gonçalves P.J.
        • Sahani M.
        • Linden J.F.
        • Hildebrandt K.J.
        Sustained activation of PV+ interneurons in core auditory cortex enables robust divisive gain control for complex and naturalistic stimuli.
        Cereb Cortex. 2021; 31: 2364-2381
        • Cardin J.A.
        • Carlén M.
        • Meletis K.
        • Knoblich U.
        • Zhang F.
        • Deisseroth K.
        • et al.
        Driving fast-spiking cells induces gamma rhythm and controls sensory responses.
        Nature. 2009; 459: 663-667
        • Toritsuka M.
        • Kimoto S.
        • Muraki K.
        • Landek-Salgado M.A.
        • Yoshida A.
        • Yamamoto N.
        • et al.
        Deficits in microRNA-mediated Cxcr4/Cxcl12 signaling in neurodevelopmental deficits in a 22q11 deletion syndrome mouse model.
        Proc Natl Acad Sci U S A. 2013; 110: 17552-17557
        • Piskorowski R.A.
        • Nasrallah K.
        • Diamantopoulou A.
        • Mukai J.
        • Hassan S.I.
        • Siegelbaum S.A.
        • et al.
        Age-dependent specific changes in area CA2 of the hippocampus and social memory deficit in a mouse model of the 22q11.2 deletion syndrome.
        Neuron. 2016; 89: 163-176
        • Beasley C.L.
        • Zhang Z.J.
        • Patten I.
        • Reynolds G.P.
        Selective deficits in prefrontal cortical GABAergic neurons in schizophrenia defined by the presence of calcium-binding proteins.
        Biol Psychiatry. 2002; 52: 708-715
        • Hashimoto T.
        • Volk D.W.
        • Eggan S.M.
        • Mirnics K.
        • Pierri J.N.
        • Sun Z.
        • et al.
        Gene expression deficits in a subclass of GABA neurons in the prefrontal cortex of subjects with schizophrenia.
        J Neurosci. 2003; 23: 6315-6326
        • Uhlhaas P.J.
        • Singer W.
        Abnormal neural oscillations and synchrony in schizophrenia.
        Nat Rev Neurosci. 2010; 11: 100-113
        • Dienel S.J.
        • Lewis D.A.
        Alterations in cortical interneurons and cognitive function in schizophrenia.
        Neurobiol Dis. 2019; 131: 104208
        • David A.
        • Malmberg A.
        • Lewis G.
        • Brandt L.
        • Allebeck P.
        Are there neurological and sensory risk factors for schizophrenia?.
        Schizophr Res. 1995; 14: 247-251
        • Fors A.
        • Abel K.M.
        • Wicks S.
        • Magnusson C.
        • Dalman C.
        Hearing and speech impairment at age 4 and risk of later non-affective psychosis.
        Psychol Med. 2013; 43: 2067-2076
        • Mason P.
        • Rimmer M.
        • Richman A.
        • Garg G.
        • Johnson J.
        • Mottram P.G.
        Middle-ear disease and schizophrenia: Case-control study.
        Br J Psychiatry. 2008; 193: 192-196
        • Zinnamon F.A.
        • Harrison F.G.
        • Wenas S.S.
        • Meyer A.F.
        • Liu Q.
        • Wang K.H.
        • et al.
        Hearing loss promotes schizophrenia-relevant brain and behavioral abnormalities in a mouse model of human 22q11.2 Deletion Syndrome.
        bioRxiv. 2019; https://doi.org/10.1101/539650