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Abstract:
Previous behavioral studies on schizophrenia demonstrated
evidence of reduced interhemispheric cooperation after bilateral
stimulation with the same material. The present study was designed
to find electrocortical correlates of impaired interhemispheric
cooperation in schizophrenic patients. Event-related Potentials of
12 schizophrenic patients and 13 healthy controls were recorded
from 65 scalp electrodes during a lexical decisiontask in which
words and pseudowords were presented tachistoscopically either to
the right or left visual field or simmultaneously to both visual
fields. In the bilateral condition, ERP data of healthy controls
showed significantly larger N200 amplitudes to words in both
hemispheres compared to schizophrenic patients. In unilateral
conditions, N200 amplitudes evoked contralateral to the stimulated
hemisphere were equally large in both groups. However, N200
amplitudes ipsilateral to the stimulated hemisphere were larger in
healthy controls than in schizophrenic patients. We conclude that
bilateral stimulation with words leads to bihemispheric activation
and interhemispheric cooperation in healthy controls. In contrast,
the present data suggest reduced interhemispheric communication
during word processing in schizophrenic patients.
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