Tuesday, June 30, 2009

Seeing the future: Natural image sequences produce "anticipatory" neuronal activity and bias perceptual report.

Perrett DI, Xiao D, Barraclough NE, Keysers C, Oram MW.
Q J Exp Psychol (Colchester). 2009 Jun 23:1-24.
Fulltext: http://www.informaworld.com/smpp/content~db=all?content=10.1080/17470210902959279

This paper relates human perception to the functioning of cells in the temporal cortex that are engaged in high-level pattern processing. We review historical developments concerning (a) the functional organization of cells processing faces and (b) the selectivity for faces in cell responses. We then focus on (c) the comparison of perception and cell responses to images of faces presented in sequences of unrelated images. Specifically the paper concerns the cell function and perception in circumstances where meaningful patterns occur momentarily in the context of a naturally or unnaturally changing visual environment. Experience of visual sequences allows anticipation, yet one sensory stimulus also "masks" perception and neural processing of subsequent stimuli. To understand this paradox we compared cell responses in monkey temporal cortex to body images presented individually, in pairs and in action sequences. Responses to one image suppressed responses to similar images for approximately 500 ms. This suppression led to responses peaking 100 ms earlier to image sequences than to isolated images (e.g., during head rotation, face-selective activity peaks before the face confronts the observer). Thus forward masking has unrecognized benefits for perception because it can transform neuronal activity to make it predictive during natural change.

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