Electrodynamic Sailing : Beating into the Solar
نویسنده
چکیده
monkey with vision occluded obtain information about its own motor activities, as would be necessary, for example, when learning new movements? In this regard it is worth considering the possibility of the operation of central feedback mechanisms. Intracentral loops located appropriately could provide a means of monitoring central efferent activity before it has emerged into the periphery. Several pathways that could fulfill this function have been demonstrated to exist both anatomically and electrophysiologically, with points of inflection involving: afferent collaterals from the medullary pyramids to the dorsal column nuclei (9), laminae 4 to 6 of the dorsal horn (10), and the deep nuclei of the cerebellum (11). Other pathways of a similar nature probably exist elsewhere in the central nervous system. Descending activity could also be converted into a return pattern of signals by electrotonic or ephaptic conduction between descending and ascending fibers in adjacent tracts (12). A number of indications have made the dorsal spinocerebellar tract a subject of interest for current study in this regard. Another possibility is that no topographic feedback whatever, whether of central or peripheral origin, is necessary for the central nervous system to obtain information about movement-producing patterns of discharge. A set of neurons need only fire, and this event by itself would be sufficient to produce the encoding of that information. Feedback return would not be necessary to reiterate the data or to report on the consequences of the discharge. These different alternatives need not be viewed as mutually exclusive. ROBERT COHN ALFRED JAKNIUNAS, EDWARD TAUB Institute for Behavioral Research, Silver Spring, Maryland 20910
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