Diminished Auditory Cortex Dynamic Range and its Clinical Correlates in First Episode Psychosis

Abstract

Background and hypothesis: There is growing appreciation for the contribution of sensory disruptions to disease morbidity in psychosis. The present study examined auditory cortex (AC) dynamic range: the scaling of neurophysiological responses to stimulus intensity, among individuals with a schizophrenia spectrum illness (FESz) and its relationship to clinical outcomes at disease onset.

Study design: Magnetoencephalography (MEG) was recorded from 35 FESz and 40 healthy controls (HC) during binaural presentation of tones at three intensities (75 dB, 80 dB, and 85 dB). MRIs were obtained to enhance cortical localization of MEG sensor-level activity. All participants completed the MATRICS cognitive battery (MCCB) and Global Functioning: Role and Social scales (GFR/GFS). Patients were administered the Positive and Negative Syndrome Scale (PANSS).

Study results: FESz exhibited reduced AC response relative to HC. Enhancement of AC activity to tones of increasing intensity was blunted in FESz relative to HC. Reduced dynamic range (85-75 dB AC response) was associated with lower GFS (r = .58) and GFR (r = .45) scores, worse MCCB performance (r = .45), and increased PANSS Negative symptom subscale scores (r = -.55) among FESz, relationships not observed with AC responses to individual tones.

Conclusion: Beyond an impaired AC response to pure tones, FESz exhibit reduced dynamic range relative to HC. This impairment was correlated with markers of disease morbidity including poorer community functioning as well as cognitive and negative symptoms. The relationship with impaired social functioning may reflect the role of AC dynamic range in decoding the emotional content of language and highlights its importance to future therapeutic sensory remediation protocols.

Keywords: auditory processing; first episode psychosis; magnetoencephalography; psychometric function; social functioning; sound intensity.

Fig. 1.

Zoomed in view of the left (A) and right (B) auditory cortex depicting localization of M100-related cortical activity. Data represent responses from all participants to the 85 dB tone, averaged across the M100 time window (80–110ms post-stimulus).

Fig. 2.

Group averages for the M100-related cortical response to the 75 dB, 80 dB, and 85 dB tones. Note that FESz has a lower thresholding scale (0.2–0.4 vs 0.25–0.5 dSPM), thereby reducing the appearance of the overall group effect.

Fig. 3.

Quantification of right and left AC activity in response to 75 dB, 80 dB, and 85 dB tones. Error bars represent SEM.

Fig. 4.

Correlations between AC dynamic range (ie, AC response to 85 dB tone minus AC response to 75 dB tone) and clinical outcomes in FESz. GF, role/social: global functioning role and social scales; PANSS, Positive and Negative Syndrome Scale (t-scores); MCCB, MATRICS Consensus Cognitive Battery (t-scores).