Contributions of visual area V4 to rapid shape detection

Abstract

Vision in foveate animals is an active process that requires rapid and constant decision-making. For example, whenever a new object of potential interest appears in the visual field, we quickly decide whether or not to inspect it by directing our eyes to the object's location. We studied the contribution of primate area V4 to these types of rapid foveation decisions. We trained <italic>Macaca mulatta</italic> to saccade to a peripherally presented shape embedded in dynamic noise as soon as the shape appeared. While the monkeys performed the task, we recorded from neurons in area V4, a visual area thought to be involved in form perception. We found that approximately half of the randomly sampled V4 neurons not only rapidly and precisely represented the appearance of this shape, but they were also predictive of the animal's saccades. In approximately seven percent of our recorded sample, individual neurons were able to predict both the delay and precision of the animal's shape detection performance, suggesting that a subset of V4 neurons may have been directly and causally contributing to task performance. To examine how groups of such neurons might act in concert, we recorded from 5 to 29 V4 neurons simultaneously during the task. While modest correlations were present between pairs of cells during visual stimulation, their magnitude did not change significantly subsequent to the appearance of a shape. We quantified the reliability and temporal precision of pairs and larger populations of neurons to signal the appearance of the shape using mutual information analyses. We found that removing correlations by shuffling across trials did not affect the reliability or timing with which pairs, or larger groups of cells, signaled the presence of a shape. Our findings suggest that a small fraction of neurons in area V4 contribute independently to rapid shape detection.