Authors:

CALDER, A.J.

Reference:

Year of publication:

2006

CBU number:

6440

Abstract:

Neurophysiological studies with macaques have identified cells in the superior temporal sulcus (STS) that respond to particular directions of gaze. A behavioural adaptation paradigm was used to explore whether a similar functional dissociation underlies gaze perception in humans. Before adaptation, observers were accurate at discerning the direction of seen gaze (5° or 10° left or right, and direct). Adaptation to 25° leftward or rightward gaze produced a powerful illusion that caused participants to mistake gaze directed towards the adapted side as direct. This pattern held despite changes in identity, head orientation, or size between the adapting and test stimuli, demonstrating that the findings do not reflect low-level effects. A similar adaptation paradigm was used with fMRI to show that the superior temporal sulcus contains separate neuronal populations tuned to different gaze directions. Leftward adaptation produced a graded response in the right anterior STS, with left gaze showing the least activation, followed by direct gaze, and right gaze the most; the converse pattern was found following rightward gaze adaptation, with right gaze showing the least activation and left gaze the most. These findings provide evidence of separable coding of different gaze directions in humans and are consistent with neurophysiological recording in non- primates.