Vector averaging occurs downstream from learning in smooth pursuit eye movements of monkeys

How are sensory-motor transformations organized in a cortical motor system? In general, sensory information is transformed through a variety of signal processing operations in the context of distinct coordinate frameworks. We studied the interaction of two distinct operations in pursuit eye movement s, learning and vector-averaging, to gain insight into their underlying coo rdinate frameworks and their sequence in sensory-motor processing. Learning was induced in the initiation of pursuit eye movements by targets that mov ed initially at one speed for 100 msec and then increased or decreased to a sustained final speed. Vector averaging was studied by comparing the initi al eye acceleration evoked by the simultaneous motion of two targets with t hat evoked by each target singly. Learning caused specific effects on the d irection of the vector-averaged responses to two-target stimuli that includ ed one target moving in the direction used to induce learning. Learned incr eases or decreases in eye acceleration caused the direction of the response s to two-targets to rotate toward or away from the learning direction. Lear ning also caused nonspecific changes in the responses to two-target stimuli . After any learning protocol, two-target responses usually became smaller, and their directions rotated away from the axis of the target motion used for learning. Quantitative analysis showed that the specific effects of lea rning were predicted most closely by a model in which vector averaging occu rs downstream from the site(s) of learning. We suggest that the pursuit sys tem creates parallel commands for potential movements to each of the target s in two-target stimuli, and that learning occurs in the coordinates of the potential movements.