RESPONSES IN VENTRAL INTRAPARIETAL AREA OF AWAKE MACAQUE MONKEY TO OPTIC FLOW PATTERNS CORRESPONDING TO ROTATION OF PLANES IN-DEPTH CAN BE EXPLAINED BY TRANSLATION AND EXPANSION EFFECTS

There is evidence that neurons in medial superior temporal area (MST) respond to rotation in depth of textured planes. MST neurons project t o the ventral intraparietal area (VIP) and the question arises whether VIP neurons are responsive to rotation in depth as well. In the prese nt study on awake monkeys, we have simulated movement of a flat board, covered with dots, by a computer. The two-dimensional images correspo nded to the projection of structured planes rotating around a fronto-p arallel axis. In the literature this stimulus is called fanning. Fanni ng effectively induced responses in VIP neurons. Most often the respon ses were nearly as strong as for translation, expansion/contraction, o r rotation, indicating that there was no special sensitivity for rotat ion in depth. For neurons, sensitive to expansion, the response to fan ning could often be explained by the positioning of the expanding part of the fanning stimulus over the area which was most responsive to ex pansion. For neurons which were direction selective to translation, th e optimal direction of fanning was usually the same as the preferred d irection for translation It is concluded that VIP neurons may be sensi tive to movement of structured planes but they are not specialized for the detection of such movement.