SENSORIMOTOR TRANSFORMATION IN A SPINAL MOTOR SYSTEM

To use sensory information from the skin to guide motor behaviour the central nervous system must transform sensory coordinates into movemen t coordinates. As yet, the basic principles of this crucial neural com putation are unclear. One motor system suitable as a model for the stu dy of such transformations is the spinal withdrawal reflex system. The spatial organization of the cutaneous input to these reflexes has bee n characterized, and we now introduce a novel method of motion analysi s permitting a quantitative analysis of the spatial input-output relat ionship in this motor system. For each muscle studied, a ''mirror-imag e'' relationship was found between the spatial distribution of reflex gain for cutaneous input and the pattern of cutaneous unloading ensuin g on contraction. Thus, there is an ''imprint'' of the movement patter n on this motor system permitting effective sensorimotor transformatio n. This imprint may indicate the presence of a learning process which utilizes the sensory feedback ensuing on muscle contraction.