Relationship between N100 amplitude and T1w/T2w-ratio in the auditory cortex in schizophrenia spectrum disorders

Schizophrenia spectrum disorders (SCZ_spect) are associated with altered function in the auditory cortex (AC), indicated by lower N100 amplitude of the auditory evoked potential (AEP). Although the neural substrate behind lower N100 amplitude remains elusive, myelination in the AC may play a role. This study compared N100 amplitude and magnetic resonance imaging (MRI) T1 weighted and T2 weighted ratio (T1w/T2w-ratio), as a proxy of myelination, in the primary AC (AC1) and secondary AC (AC2) between SCZ_spect (n = 33, 48% women) and healthy controls (HC, n = 144, 49% women). We also examined the associations between N100 amplitude and T1w/T2w-ratios across groups. We finally explored N100 amplitude and T1w/T2w-ratios and the N100-T1w/T2w-ratio associations between male and female SCZ_spect and HC. N100 amplitude was significantly lower in male SCZ_spect compared to male HC (p = 0.01) and nominally lower in SCZ_spect compared to HC (p = 0.03). However, T1w/T2w-ratios in AC1/AC2 did not differ between groups, and no association was found between N100 amplitude and T1w/T2w-ratio in either group. These findings suggest that sex-specific effects should be considered in SCZ_spect neurophysiology research. Our results do not support the hypothesis of an association between lower N100 amplitude and lower T1w/T2w-ratio in the AC1/AC2 in SCZ_spect. More precise assessments of intracortical myelin are needed to understand the relationship between N100 amplitude and cortical myelination in the AC in SCZ_spect and in healthy controls.