Electrodermal responsivity distinguishes ERP activity and symptom profile in schizophrenia

Traditional averaging of late component Event Related Potentials (ERPs) might obscure important psychophysiological subprocesses underlying schizophrenia disturbances in cognitive functioning. One such subprocess could be the active orientation of attention to significant or novel stimuli. In this study, we used skin conductance responses (SCRs) to index orienting responses (ORs). ERP activity was examined in relation to concomitant ORs in a schizophrenia and nonpsychiatric control group. Schizophrenia responses were considered with respect to the Reality Distortion, Disorganisation and Psychomotor Poverty syndromes.

Forty schizophrenia and 40 age and sex matched control subjects were tested. The three schizophrenia syndromes were derived from a principal component analysis of Positive and Negative Syndrome Scale (PANSS) ratings. Auditory ERPs (N100, N200, P200, P300) were elicited using a conventional auditory oddball paradigm, and electrodermal SCR data were acquired simultaneously.

ERP data were sub-averaged according to the presence/absence of an OR. For both 'with-' and 'without-OR' ERPs, schizophrenia subjects as a group showed reduced N100 (associated with vigilance level) and N200 (associated with response selection) amplitude, and for with-OR responses, they showed an additional reduction in P300 (context processing). Concerning schizophrenia syndromes, Reality Distortion was related primarily to frontal disturbances (earlier N100/N200 latency and decreased P200/P300 amplitude), and Psychomotor Poverty to a generally delayed P300 latency. Similarly delayed P300 in Disorganisation was explained by medication effects. There were no associations with syndromes for without-OR ERPs.

These results suggest that schizophrenia syndromes are dissociated with regard to both the direction and nature of speed of information processing disturbances, in relation to task-relevant information that produces active orientation.