Modulation of neuronal activity with cue-invariant shape discrimination in the primate superior temporal sulcus.

Shape perception can be achieved based on various cues such as luminance, color, texture, depth and motion. To investigate common neural mechanisms underlying shape perception cued by various visual attributes, we examined single-neuron activity in the monkey anterior superior temporal sulcus (STS) in response to shapes defined by luminance and motion cues during shape discrimination. We found cortical mapping with respect to selectivity for shapes as well as for direction of motion in the STS. About 90% of shape-selective neurons were located in the lower bank of STS (lSTS) assigned to the ventral pathway, while about 80% of direction-selective neurons existed in the upper bank of STS (uSTS) assigned to the dorsal pathway. The neurons showing selectivity for both shape and motion coexisted in lSTS as well as uSTS. This result indicates that integration or convergence of shape information and motion information can occur in both banks of STS. About 90% of STS neurons showing selectivity both for shapes defined by luminance cue and for shapes defined by motion cue were located in lSTS. They showed a highly similar shape preference between the different visual attributes, indicating cue-invariant shape selectivity. The cue-invariant shape-selectivity was modulated with target selection as well as with discrimination performance of monkeys. These results suggest that lSTS could be involved in cue-invariant shape discrimination, but not the uSTS.