Auditory sensory gating deficit and cortical thickness in schizophrenia

Both an EEG P50 sensory gating deficit and abnormalities of the temporal lobe structure are considered characteristic of schizophrenia. The standard P50 sensory gating measure does not foster differential assessment of left- and right-hemisphere contributions, but its analogous MEG M50 component may be used to measure gating of distinct auditory source dipoles localizing to left- and right-hemisphere primary auditory cortex. The present study sought to determine how sensory gating ratio may relate to cortical thickness at the site of the auditory dipole localization. A standard auditory paired-click paradigm was used during MEG for patients (n=22) and normal controls (n=11). Sensory gating ratios were determined by measuring the strength of the 50 ms response to the second click divided by that of the first click (S2/S1). Cortical thickness was assessed by two reliable raters using 3D sMRI. Results showed that: (1) patients had a P50 and left M50 sensory gating deficit relative to controls; (2) cortex in both hemispheres was thicker in the control group; (3) in schizophrenia, poorer left-hemisphere M50 sensory gating correlated with thinner left-hemisphere auditory cortical thickness; and (4) poorer right-hemisphere M50 auditory sensory gating ratio correlated with thinner right-hemisphere auditory cortical thickness in patients. The MEG-assessed hemisphere-specific auditory sensory gating ratio may be driven by this structural abnormality in auditory cortex.