Reduced novelty-P3 associated with increased behavioral distractibility in schizophrenia.

Behavioral and electrophysiological brain responses were used to examine the relationship between the vulnerability to distraction and the orienting response in schizophrenia. Nineteen schizophrenics and nineteen matched healthy controls were instructed to ignore task-irrelevant auditory stimuli while they classified capital letters and digits. The auditory sequences contained repetitive standard tones occasionally replaced by complex novel sounds. Relative to controls, patients showed an increased behavioral distraction, as indicated by a larger response time increase caused by novel sounds, and a disturbance in the attention orienting toward distracting stimuli, as indicated by a reduced novelty-P3. This behavioral-electrophysiological dissociation may stem from a limited pool of available resources. Thus, the few attentional resources directed toward novel stimuli would be sufficient to cause an important decrease of the similarly reduced amount of resources assigned to task-relevant stimuli, resulting in a striking impairment of the ongoing task performance.