Temporal assimilations during bi-manual movements in non-impaired and Parkinsonian individuals

Abstract

When bi-lateral movements of differing difficulty are performed as rapidly as possible the "easier" of the two limbs slows down and is attracted to the temporal structure of the more difficult movement. Simultaneous movements are expected to be severely compromised in Parkinson's Disease (PD). The purpose of this study was to investigate whether Parkinsonians elicit temporal assimilations in the belief that an assimilatory response may facilitate simultaneous bi-lateral control in PD.Temporal attractions were elicited by the non-impaired subjects during the bi-lateral task. The increased movement duration of the "easy" limb was the consequence of a contralateral motor command interference. The Parkinsonians failed to generate sufficient contralateral shoulder torque to interfere with the metrical structure of the "easier" task comprising the bi-lateral movements. These observations suggest that temporal assimilations elicited by this class of movements are the result of a motor command interference and not the effect of a restructuring of the movements metrics