Motion sensitive cells in the macaque superior temporal polysensory area: response discrimination between self-generated and externally generated pattern motion.

It was previously shown [17] that visual movement sensitive neurons lacking selectivity in the anterior parts of the dorsal superior temporal sulcus (STP) of monkeys exhibited selective responses to externally moved objects and failed to respond to the sight of the animal's own limb movements. This paper describes a series of experiments in which a monkey was trained to operate an apparatus that produced visual motion of a projected two-dimensional patterned stimulus. Single unit responses from STP were recorded and responses to visual motion, produced externally by the experimenter, were compared to the responses to visual motion (of the same pattern) produced by the monkey itself. The majority of the movement sensitive cells giving reliable responses to the pattern motion responded statistically more strongly to the experimenter-induced motion than to the motion induced by the monkey itself. The cell responses were observed not to be affected by the motion velocity and the monkey's motor activity (handle rotation without any visual stimulation) did not affect the cell's spontaneous activity. The results indicate that the response discrimination of STP cells between externally and self-induced stimulus motion is not based on form sensitivity. Moreover, the mechanism which produces the described response selectivity is not only limited to naturally occurring visual consequences of the monkey's own motor activity but is plastic and can extend to arbitrary associations between the monkey's movements and consequent visual motion.