Hemispheric asymmetry in schizophrenia: A "dual deficits" model

Background: The aim was 1) to investigate left hemisphere functional integr ity for auditory language processing in schizophrenic patients; and 2) to i nvestigate the interaction between brain laterality and attentional process ing by having subjects shift attention to the left or right ear. Methods: The subjects were 33 schizophrenic inpatients, and 33 healthy comp arison subjects with the same age, handedness, and gender distribution as t he patient subjects. All subjects were rested with dichotic listening (DL) to consonant-vowel syllables, which is a measure of lateralized temporal lo be language processing. The subjects were rested under three different atte ntional conditions: a non-forced attention condition, attention focused to the right ear stimulus, and attention focused to the left ear stimulus. Results: The main findings were 1) an absence of the expected right ear adv antage in the schizophrenic group during the non-forced attention condition ; and 2) a failure to modify DL performance through shifting of attention t o either the right or left ear. The comparison group showed a right ear adv antage during the non-forced and forced-right attention conditions (increas ed right ear advantage during the forced-right condition), and a left ear a dvantage during the forced-left attention condition. There were no signific ant effects of handedness. Conclusions: This pattern of results may indicate a "dual deficit" involvin g both automatic and controlled processing deficits in schizophrenia. Biol Psychiatry 1999;45: 76-81 (C) 1999 Society of Biological Psychiatry.