Possible role for recurrent interactions between expansion and contraction cells in MSTd during self-motion perception in dynamic environments

Cortical area MSTd contains cells sensitive to the radial expansion and contraction motion patterns experienced during forward and backward self-motion. We investigated the open question of whether populations of MSTd cells tuned to expansion and contraction interact through recurrent connectivity, which may play important roles in postural control and resolving heading in dynamic environments. We used a neural model of MSTd to generate predictions about the consequences of different types of interactions among MSTd expansion and contraction cells for heading signals produced in the case of self-motion in the presence of a retreating object-a stimulus that recruits both expansion and contraction MSTd cell populations. Human heading judgments from a psychophysical experiment that we conducted were consistent only with the MSTd model that contained recurrent connectivity within and between expansion and contraction cell populations. The model and human heading judgments were biased in the direction of the object motion when the object crossed the observer's future path and biased in the opposite direction when the object did not cross the path. We conclude that recurrent interactions among expansion and contraction cells in MSTd provide a plausible mechanism to support robust self-motion through dynamic environments.