AERPs and clinical evolution of thought disorders over five years

In a selective attention task, 21 Subjects detected rare randomized targets (P = 0.02) in a set of randomized standard tones. In one condition, Subjects focused their attention and detected targets in one ear, ignoring the other ear, and vice versa in the next condition. AERPs (auditory event-related potentials) were recorded at 5 electrode sites (10-20 system), at Fz, Cz, Pz, C3, C4, in two conditions varying speed of stimulation (randomized interstimulus intervals of 250-750 ms and 750-1500 ms). One group of 7 schizophrenics with the major syndrome of formal thought disorder (+FTD) was compared to 7 schizophrenics without the FTD syndrome (-FTD), and to 7 controls. The schizophrenic group was matched for age, education, sex, medication, hospitalization and intelligence score on abbreviated WAIS test. Ss were re-tested after 5 years following identical experimental and counterbalancing method to the pre-test. At re-test, similarly to pre-test, schizophrenics' AERPs showed smaller amplitudes, longer latencies, smaller attention effects than normals. -FTD schizophrenics showed intermediate values between the +FTD patients and normals. At retest, +FTD schizophrenics showed an aggravation of these AERP abnormalities while -FTD patients seemed to improve with larger amplitudes, faster latencies and better attention effects than at pre-test. Differential correlations between clinical and AERP indices indicated a dissociation between neurophysiological and clinical evolution: factors of dissociation included Andreasen's positive and negative indices of thought disorder, neuropsychological indices on the Luria-Nebraska scales, and severity of psychotic symptoms.