Planning and efferent components in the coding of movement.

Two experiments were carried out to assess the cognitive contribution of a movement plan and its relationship to efferent-command information in explaining the superior accuracy of preselected movement. Subjects performed under conditions which differed with regard to efferent information (active versus passive) and the availability of a movement plan (preselected, subject defined vs. constrained, experimenter defined). In both experiments active preselection had significantly smaller reproduction errors than any other combination, indicating that the planning process in itself was insufficient to facilitate movement coding. The findings were interpreted in terms of the sometimes-synonymously viewed concepts of central monitoring of efference, efference copy, and corollary discharge. The latter notion, that a central signal occurs prior to movement which acts to facilitate the processing of information, seemed to provide the most appropriate account of the present data. The experiments reported here are a portion of a Ph.D. dissertation submitted to the University of Wisconsin-Madison under the supervision of George E. Stelmach, to whom appreciation is extended. Support for the research was provided by Grant MH 22081-01 from the National Institute of Mental Health and by Grant NE-G-3-0009 from the National Institute of Education. However, the opinions expressed herein do not necessarily reflect the position or policies of the above granting agencies and no official endorsement of them should be inferred. The author would like to thank Shelley Smith who assisted with data collection in these experiments.