Effects of accuracy constraints on reach-to-grasp movements in cerebellar patients
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Reach-to-grasp movements of patients with pathology restricted to the cerebellum were compared with those of normal controls. Two types of paradigms with different accuracy constraints were used to examine whether cerebellar impairment disrupts the stereotypic relationship between arm transport and grip aperture and whether the variability of this relationship is altered when greater accuracy is required. The movements were made to either a vertical dowel or to a cross bar of a small cross. All subjects were asked to reach for either target at a fast but comfortable speed, grasp the object between the index finger and thumb, and lift it a short distance off the table. In terms of the relationship between arm transport and grip aperture, the control subjects showed a high consistency in grip aperture and wrist velocity profiles from trial to trial for movements to both the dowel and the cross. The relationship between the maximum velocity of the wrist and the time at which grip aperture was maximal during the reach was highly consistent throughout the experiment. In contrast, the time of maximum grip aperture and maximum wrist velocity of the cerebellar patients was quite variable from trial to trial, and the relationship of these measurements also varied considerably. These abnormalities were present regardless of the accuracy requirement. In addition, the cerebellar patients required a significantly longer time to grasp and lift the objects than the control subjects. Furthermore, the patients exhibited a greater grip aperture during reach than the controls. These data indicate that the cerebellum contributes substantially to the coordination of movements required to perform reach-to-grasp movements. Specifically, the cerebellum is critical for executing this behavior with a consistent, well-timed relationship between the transport and grasp components. This contribution is apparent even when accuracy demands are minimal.
Key wordsCerebellum Reaching Grasping Coordination Human
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- Bloedel JR, Bracha V, Shimansky Y, Milak MS (1996) The role of the cerebellum in the acquisition of complex volitional fore-limb movements. In: Bloedel JR, Ebner TJ, Wise SP (eds) The acquisition of motor behavior in vertebrates. MIT press, Cambridge, MA, pp 319–342Google Scholar
- Dichgans J, Diener HC (1984) Clinical evidence for functional compartmentalization of the cerebellum. In: Bloedel JR, Dichgans JD, Precht W (eds) Cerebellar functions. Springer, Berlin Heidelberg New York, pp 126–147Google Scholar
- Jeannerod M (1981) Intersegmental coordination during reachig at natural visual objects. In: Long J, Baddeley A (eds) Attention and performance IX. Erlbaum, Hillsdale, pp 153–168Google Scholar
- Rand MK, Shimansky Y, Stelmach GE, Brach V, Bloedel JR (1999) Effects of accuracy constraints on reach-to-grasp movements in cerebellar patients. Soc Neurosci Abstr 25:369Google Scholar
- Thach WT, Perry JG, Kane SA, Goodkin HP (1993) Cerebellar nuclei: rapid alternating movement, motor somatotopy, and a mechanism for the control of muscle synergy. Rev Neurol (Paris) 149:607–628Google Scholar
- Trouche E, Beaubaton D (1980) Initiation of a goal-directed movement in the monkey. Role of the cerebellar dentate nucleus. Exp Brain Res 40:311–321Google Scholar
- Van Kan PLE, Horn KM, Gibson AR (1994) The importance of hand use to discharge of interpositus output neurons of the monkey. J Physiol (Lond) 480:171–190Google Scholar