Specific imbalance of right and left sided motor neuron excitability in schizophrenia.

Fifty-three psychiatric patients, 16 with schizophrenia, 19 with affective disorder, and 19 with schizo-affective disorder were diagnosed by Research Diagnostic Criteria. Hoffmann reflex recovery curves were measured in the right and left legs of each patient. In both affective disorder and schizo-affective disorder, recovery curve height in the right and left legs was highly correlated. In schizophrenia, recovery curve height in the right and left legs was not correlated. These results demonstrate a right-left asymmetry in motor neuron excitability specific to schizophrenia. The findings are compatible with a deficit in hemispheric transfer that is unique to schizophrenia. Other interpretations can be made, including diffuse cortical or subcortical dysfunction in schizophrenia which disrupts transfer or interpretation or intrahemispheric communication.