Motoneuron excitability in psychiatric patients.

The excitability at the alpha-motoneuron pool was studied by measuring the spinal monosynaptic reflex responses of soleus muscle to paired stimuli in psychiatric patients and controls. Patients showed significant alterations in the recovery of excitability when compared with normal volunteers. Specifically, the value for the peak of "secondary facilitation" was reduced in 5 of 8 chronic schizophrenic patients, while the following trough in the recovery cycle was reduced in 9 of 18 acutely schizophrenic patients. Drug effects were studied in 10 patients. Phenothiazine antipsychotic medication tended to enhance recovery of excitability. Patients of all types showed alterations of excitability. The altered excitability may relfect one aspect of a widespread abnormality of CNS function or may be a specific response to a supraspinal defect in neurophysiological activity in psychotic patients.