We show that populations of visually responsive cells in the anterior part of the superior temporal sulcus (STSa) of the macaque monkey code for the sight of both specific articulated body actions and the consequent articulated static body postures. We define articulated actions as actions where one body part (e.g. a limb or head) moves with respect to the remainder of the body which remains static; conversely non-articulated actions are actions where the equivalent body parts do not move with respect to each other but move as one. Similarly, articulated static body postures contain a torsion or rotation between parts, while non-articulated postures do not. Cells were tested with the sight of articulated and non-articulated actions followed by the resultant articulated or non-articulated static body postures. In addition, the static body postures that formed the start and end of the actions were tested in isolation. The cells studied did not respond to the sight of non-articulated static posture, which formed the starting-point of the action, but responded vigorously to the articulated static posture that formed the end-point of the action. Other static postures resembling the articulated end-point posture, but which were in a more relaxed muscular state (i.e. non-articulated), did not evoke responses. The cells did not respond to body actions that were less often associated with the effective static articulated postures. Our results suggest that the cells' responses were related to the implied action rather than the static posture per se. We propose that the neural representations in STSa for actual biological motion may also extend to biological motion implied from static postures. These representations could play a role in producing the activity in the medial temporal/medial superior temporal (V5(MT)/MST) areas reported in fMRI studies when subjects view still photographs of people in action.
Emotional facial expressions are immediate indicators of the affective dispositions of others. Recently it has been shown that early stages of social perception can already be influenced by (implicit) attributions made by the observer about the agent’s mental state and intentions. In the current study possible mechanisms underpinning distortions in the perception of dynamic, ecologically-valid, facial expressions were explored. In four experiments we examined to what extent basic perceptual processes such as contrast/context effects, adaptation and representational momentum underpinned the perceptual distortions, and to what extent ‘emotional anticipation’, i.e. the involuntary anticipation of the other’s emotional state of mind on the basis of the immediate perceptual history, might have played a role. Neutral facial expressions displayed at the end of short video-clips, in which an initial facial expression of joy or anger gradually morphed into a neutral expression, were misjudged as being slightly angry or slightly happy, respectively (Experiment 1). This response bias disappeared when the actor’s identity changed in the final neutral expression (Experiment 2). Videos depicting neutral-to-joy-to-neutral and neutral-to-anger-to-neutral sequences again produced biases but in opposite direction (Experiment 3). The bias survived insertion of a 400 ms blank (Experiment 4). These results suggested that the perceptual distortions were not caused by any of the low-level perceptual mechanisms (adaptation, representational momentum and contrast effects). We speculate that especially when presented with dynamic, facial expressions, perceptual distortions occur that reflect ‘emotional anticipation’ (a low-level mindreading mechanism), which overrules low-level visual mechanisms. Underpinning neural mechanisms are discussed in relation to the current debate on action and emotion understanding.
We show that under natural viewing, the responses of cells the temporal lobe of the macaque to the sight of static head body postures is controlled by the sight of immediately actions. Cells in the anterior part of the superior sulcus responded vigorously to the sight of a face or posture that followed a particular body action, but not when it followed other actions. The effective action or posture presented in isolation or in different sequences failed to produce a response. Our results demonstrate that cells in the temporal cortex could support the formation of expectations about impending behavior of others.
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