Abnormal visual--vestibular interactions in psychosis.

Vestibular reactivity and suppression of caloric nystagmus by visual fixation were examined in 40 psychiatric patients (36 schizophrenics and 4 manic-depressives) and 20 normal control subjects. Indices of reactivity commonly considered to reflect vestibular integrity, namely, slow-phase velocity and bilateral symmetry of response, did not discriminate patients from controls. However, response irregularities in the form of dysrhythmia and slower velocity of the nystagmus fast (saccadic) component were present to a significant degree in patients. Visual fixation effectively suppressed caloric nystagmus in normal controls, but not in hospitalized patients. This failure of fixation suppression was most marked in patients showing active symptomatology. These results indicate a central regulatory dysfunction of visual-vestibular interaction in psychiatric patients which varies with intensity of psychotic symptomatology and which does not seem attributable to medication or attentional factors.