Deficits of ideokinetic praxis in chronic schizophrenics on a modified version of the Luria-Nebraska Motor Scale

One disturbance of motility in schizophrenia is the blocking of voluntary action, or ambitendency. Although the traditional explanation for this disorder is psychological, the documentation of psychomotor slowing in the literature suggests the possibility of a neurologic pathogenesis. It was hypothesized that disconnection between the ideatory and motor components of a voluntary action described as ambitendency is similar to the ideokinetic apraxia of disease of the left frontal cortex. It was also hypothesized that because of this presumed anatomical locus, manifestation of ideokinetic apraxia in schizophrenia would be correlated with corticomotor slowing of the dominant hand. To test these hypotheses, a modified version of the Motor Scale of the Luria-Nebraska Neuropsychological Examination and the Finger Tapping Test of the Halstead-Reitan Neuropsychological Battery were administered to 10 chronic undifferentiated schizophrenics, 10 paranoid schizophrenics, 10 patients with major depressive disorders, 10 patients with mixed personality disorders, and 10 normals. Both chronic schizophrenics and major depressives demonstrated a significant frequency of ideokinetic apraxia in comparison with the other groups. Age was found to correlate positively with ideokinetic apraxia in the depressives, suggesting that such symptoms may be an artifact of the aging process in these subjects. Ideokinetic apraxia was correlated with slowing of the dominant hand in the chronic schizophrenics, suggesting a neurologic rather than a psychologic basis for their blocking of voluntary action. No group demonstrated a significant incidence of ideational apraxia.