The Effects of Prolonged Stimulus Repetition with Repeated Switching of Target Status on the Orienting Response in Schizophrenia and Depression

Scophrenic patients are frequently orienting nonresponders to innocuous stimuli, become responsive to significant target signals, and become hyporesponsive again on prolonged repetition. We wish to a) determine whether schizophrenic patients can display orienting response (OR) flexibility, responding to newly designated targets and ceasing to respond to newly designated nontargets; b) determine whether renewed hyporesponding can be averted with reminders of target relevance and repeated introduction of new targets; and c) compare schizophrenics with depressives and normal controls. Fifty schizophrenics (14 drug free), 50 depressives (20 drug free), and 50 normal controls receive four trial blocks involving the same sequence of 16 1000− or 2000-Hz tones delivered to either the right or left ear. A subsample of each group (N = 14) receives all blocks as a simple habituation series; others (N = 36) have to press a pedal for designated target signals (left ear or right ear, 1000 Hz or 2000 Hz), ignoring all nontarget tones. On each trial block, a new target signal is defined, and previous targets are discarded. Skin conductance and finger pulse amplitude analyses are presented. Both patient groups show enhanced ORs to newly relevant targets and ceased ORs to newly irrelevant former targets as well as normals. Both show OR decline with target repetition despite reminders and new targets.