Abstract
The superior temporal sulcus (STS) in the human and monkey is sensitive to the motion of complex forms such as facial and bodily actions. We used functional magnetic resonance imaging (fMRI) to explore network-level explanations for how the form and motion information in dynamic facial expressions might be combined in the human STS. Ventral occipitotemporal areas selective for facial form were localized in occipital and fusiform face areas (OFA and FFA), and motion sensitivity was localized in the more dorsal temporal area V5. We then tested various connectivity models that modeled communication between the ventral form and dorsal motion pathways. We show that facial form information modulated transmission of motion information from V5 to the STS, and that this face-selective modulation likely originated in OFA. This finding shows that form-selective motion sensitivity in the STS can be explained in terms of modulation of gain control on information flow in the motion pathway, and provides a substantial constraint for theories of the perception of faces and biological motion.
Highlights
Humans and other animals effortlessly recognize facial identities and actions such as emotional expressions even when faces continuously move
We include these tests here for completeness and to illustrate the quantitative patterns of means within the voxels identified in the regions of interest (ROIs) our main conclusions from the ROI analyses are drawn from orthogonal ANOVA effects to preclude biased inferences
We show that motion sensitivity to facial form in the superior temporal sulcus (STS) was best explained by a dynamic causal modeling (DCM) where transmission of motion information from V5 to the STS is gated or modulated by information about facial form
Summary
Humans and other animals effortlessly recognize facial identities and actions such as emotional expressions even when faces continuously move. Brain representations of dynamic faces may be manifested as greater responses in the superior temporal sulcus (STS) to facial motion than motion of nonface objects (Pitcher et al 2011), suggesting localized representations that combine information about motion and facial form This finding relates to a considerable literature on “biological motion,” which studies how the complex forms of bodily actions are perceived from only the motion of light points fixed to limb joints, with form-related texture cues removed (Johansson 1973). The mechanisms by which STS neurons come to be sensitive to the motion of some forms, but not others, remains a matter of speculation (Giese and Poggio 2003)
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