Psychophysical and electrophysiological assessment of early visual processing and emotion recognition deficits in schizophrenia

Previous data suggest that patients with schizophrenia have preferential magnocellular (M) versus parvocellular (P) visual dysfunction. The goal of Experiment 1 was to characterize M-stream impairment in the patient population using a novel approach. Contrast thresholds at varying luminance levels were investigated. M- and P-biased responses were examined by using scotopic and photopic luminance conditions, respectively. Patients exhibited contrast threshold deficits during scotopic conditions, indicative of M-stream dysfunction. Further, the pattern of contrast threshold responses at photopic levels indicated relatively preserved patient P-pathway functionality.;Experiment 2 used separate behavioral and electrophysiological paradigms to investigate contributions of low level visual pathway dysfunction in patients to emotion perceptual processing deficits. Contrast response curves for the dorsal (P1) and ventral (N170) pathways were elicited in response to contrast manipulated emotional faces. Results showed that the dorsal P1's pattern of response was impaired in patients while their N170 contrast response curves remained intact. Contributions of visual pathway dysfunction to impaired emotion recognition and affect-related processing, as indexed by the P250 amplitude, were then assessed. P250 activity in patients was reduced at all contrasts. Overall, across groups, the P1 component predicted both P250 amplitude and emotion recognition ability. Taken together, these data support the hypothesis that emotion recognition deficits in patients result from M/dorsal stream dysfunction.;Experiment 3 examined the spatial-temporal oscillatory dynamics of schizophrenia patients during processing of complex visual stimuli. FFT spectrum activity and underlying generators of the delta, theta and alpha oscillatory frequencies were first assessed. Activity in the pre and post-stimulus intervals, and the ratio between them (event-related de/synchronization: ERD/ERS) were also evaluated. FFT data revealed controls had significantly greater alpha band activation in posterior electrodes as compared to patients. Conversely, patients exhibited greater theta-band activation over anterior electrodes versus controls. Topographical analysis suggested patients had abnormal underlying neural generators that gave rise to impaired theta and alpha-band activity. Further, instantaneous delta-band activity was significantly greater in patients during pre and post-stimulus intervals, possibly reflecting an overall generalized deficit. Finally, the data revealed that patients had a substantially reduced alpha ERD, highlighting their impairment in low level visual cortical gating mechanisms during processing of visual sensory inputs.