In this study, we measured traditional late components of the Event Related Potential (ERP: N 100, P 200, N 200 and
P 300) in a conventional auditory oddball paradigm, but additionally and simultaneously assessed electrodermal "orienting reflexes (
ORs)" in 40 patients with
schizophrenia and 40 age and gender matched normal controls. The single epoch ERPs that did and did not evoke an OR, were sub-averaged separately. The control subjects (but not the patient group), revealed delayed
P 300 latency in the ERP sub-averages without
ORs (ERP-OR), compared with ERP sub-averages with
ORs (ERP+OR). Between-group analysis showed reduced N 100, N 200 and
P 300 amplitudes (as well as delayed
P 300 latency) in the ERP+OR sub-average in patients with
schizophrenia. In the ERP-OR sub-average, the patient group also had smaller N 100, N 200 and
P 300 amplitudes, but larger P 200 amplitude (compared with normal controls). This study shows the potential to tease out physiologically based OR sub-processes, by simultaneous acquisition and analysis of ERPs and autonomic electrodermal activity. Such ERP sub-averages (based on autonomic responses) highlight that multiple processes overlap across the trial, and their delineation may elucidate more specific patterns of disturbance in
schizophrenia, than traditional averaged measures.