Abnormal laterality in schizophrenics and their parents.

Previous studies found that schizophrenics do not show the normal right ear-left hemisphere perceptual advantage on language-related dichotic tests of lateralized cerebral function. We report evidence of a similar abnormality in non-schizophrenic parents of schizophrenic patients. Perceptual asymmetry was first measured with a dichotic word test which had previously yielded differences between schizophrenics and controls. The parents (n = 18) demonstrated a lower right ear advantage (REA) than controls (n = 10) (p = 0.05), but performed similarly to their schizophrenic offspring (n = 10). The same subjects were given two additional tests. Neutral words were paired with words of a positive emotional valence in one test, and with words of a negative emotional valence in the other. On these two tests, the parents were more similar to the controls than to their offspring with the schizophrenics demonstrating a lower REA than their parents (p = 0.005) on the negative test. These results suggest that schizophrenics and their parents have similar abnormalities in hemispheric activation at baseline only, but when listening to words with negative emotional valence, only the schizophrenics demonstrate a further decrease in left hemispheric activation.