Cerebral Cortex Advance Access published online on July 16, 2008
Cerebral Cortex, doi:10.1093/cercor/bhn109
Functional Differentiation of Macaque Visual Temporal Cortical Neurons Using a Parametric Action Space
1 Laboratorium voor Neuro- en Psychofysiologie, K.U. Leuven, Belgium, 2 Department of Psychology, University of Glasgow, UK
Address correspondence to Dr Rufin Vogels, Laboratorium voor Neuro- en Psychofysiologie, K.U. Leuven Medical School, Campus Gasthuisberg, O&N2, Herestraat 49, Bus 1021, 3000 Leuven, Belgium. Email: Rufin.Vogels{at}med.kuleuven.be.
Neurons in the rostral superior temporal sulcus (STS) are responsive to displays of body movements. We employed a parametric action space to determine how similarities among actions are represented by visual temporal neurons and how form and motion information contributes to their responses. The stimulus space consisted of a stick-plus-point-light figure performing arm actions and their blends. Multidimensional scaling showed that the responses of temporal neurons represented the ordinal similarity between these actions. Further tests distinguished neurons responding equally strongly to static presentations and to actions ("snapshot" neurons), from those responding much less strongly to static presentations, but responding well when motion was present ("motion" neurons). The "motion" neurons were predominantly found in the upper bank/fundus of the STS, and "snapshot" neurons in the lower bank of the STS and inferior temporal convexity. Most "motion" neurons showed strong response modulation during the course of an action, thus responding to action kinematics. "Motion" neurons displayed a greater average selectivity for these simple arm actions than did "snapshot" neurons. We suggest that the "motion" neurons code for visual kinematics, whereas the "snapshot" neurons code for form/posture, and that both can contribute to action recognition, in agreement with computation models of action recognition.
Key Words: biological motion inferotemporal cortex monkey movement single cell superior temporal sulcus