| Summary: | Perceiving the direction of another's attention is a critical component of normal social behaviour. Seminal electrophysiology studies demonstrated that single cells in macaque superior temporal sulcus (STS) are tuned to specific directions of social cues, including gaze direction, head view, and body posture. Furthermore, a subset of such neurons respond to a single direction across multiple cues, suggesting that the code is driven by the direction of another's social attention regardless of how this is conveyed. Attempts to reveal similar gaze representations in humans using fMRI have provided mixed results. This thesis describes research where multivariate pattern analysis (MVPA) methods are applied to fMRI data in order to better explain how the human brain and particularly STS codes perceived gaze direction. After describing the MVPA methods applied in this thesis, I first demonstrate that fMRI response patterns in anterior STS distinguish between the direction of dynamic head turns, but not between the direction of rotation in non-social ellipsoids. In subsequent work, anterior STS is found to code the direction of another's gaze in a head view-invariant manner, thus demonstrating a potential parallel to previous macaque evidence for single cells that code the direction of another's attention. However, comparisons that run both across species (macaque, human) and methods (electrophysiology, fMRI) are problematic. To overcome this limitation I next tested whether macaque STS distinguishes gaze direction and head view when responses are measured with fMRI. In conclusion, this thesis demonstrates the utility of applying MVPA to fMRI data to reveal socially-relevant representations of the direction of another's attention. The thesis particularly highlights anterior STS as a key region in supporting direction-specific representations of social cues. These results advance our understanding of how the brain codes socially-relevant information, and highlight possible similarities and dissimilarities between humans and macaques.
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