Impairment of temporal organization of speech in basal ganglia diseases.

Absolute and relative speech timing were examined in patients suffering from Parkinson's, Huntington's, and Wilson's disease. The task was to speak a standard sentence 10 times, first slowly, and then successively faster up to maximum rate. All patient groups had low maximal speech rates and showed decreased variability of speech rate. The duration of pauses between words was the same as in normals and the relative time structure of the test sentence was basically preserved. For comparison, two cases with nonfluent aphasia had even slower speech rates, large increases in pause duration, and major changes in relative speech timing. The results show the same type of alterations of the temporal organization of speech as those characteristic for rapid alternating limb movements in such patients. They support the view that the speech and skeletomotor systems share common neural control modes despite fundamental biomechanical differences. The common denominator between the speech and the skeletomotor disturbances in basal ganglia diseases may be the undamping and slowing of a fast central oscillator.