TRANSFER OF CODED INFORMATION FROM SENSORY TO MOTOR NETWORKS

During sensory-guided motor tasks, information must be transferred fro m arrays of neurons coding target location to motor networks that gene rate and control movement. We address two basic questions about this i nformation transfer. First, what mechanisms assure that the different neural representations align properly so that activity in the sensory network representing target location evokes a motor response generatin g accurate movement toward the target? Coordinate transformations may be needed to put the sensory data into a form appropriate for use by t he motor system. For example, in visually guided reaching the location of a target relative to the body is determined by a combination of th e position of its image on the retina and the direction of gaze. What assures that the motor network responds to the appropriate combination of sensory inputs corresponding to target position in body- or arm-ce ntered coordinates? To answer these questions, we model a sensory netw ork coding target position and use it to drive a similarly modeled mot or network. To determine the actual motor response we use decoding met hods that have been developed and verified in experimental work. We de rive a general set of conditions on the sensory-to-motor synaptic conn ections that assure a properly aligned and transformed response. The a ccuracy of the response for different numbers of coding cells is compu ted. We show that development of the synaptic weights needed to genera te the correct motor response can occur spontaneously through the obse rvation of random movements and correlation-based synaptic modificatio n. No error signal or external teaching is needed during this process. We also discuss nonlinear coordinate transformations and the presence of both shifting and nonshifting receptive fields in sensory/motor sy stems.