Although electrophysiological and neuroimaging studies have revealed different neural populations that are broadly tuned to different views of faces, it is unclear if these neurons code aspects of face shape or code only head position or gaze direction. Some studies investigating this issue using face aftereffects have interpreted the generalisability of aftereffects across different viewpoints as evidence for viewpoint-invariant coding of face shape. Others, however, have interpreted a significant reduction in the magnitude of aftereffects when generalising across viewpoints, and opponent aftereffects for mirror-reversed 3/4 views, as evidence for viewpoint-dependent coding of face shape. Here we show it is possible to simultaneously induce opposite aftereffects for 3/4 left and front views of faces with manipulated mouth position. For example, simultaneous adaptation to 3/4 left views with raised mouth position and front views with lowered mouth position caused raised mouth position to appear more normal for 3/4 left views of novel faces, but less normal for front on views. Furthermore, adaptation to 3/4 left views with raised mouth position caused lowered mouth position to appear more normal in 3/4 right views. These findings suggest that there are neural populations that are tuned to optimally respond to viewpoint-specific aspects of face shape.
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