Tuesday, June 30, 2009

Representing the forest before the trees: a global advantage effect in monkey inferotemporal cortex.

Sripati AP, Olson CR.
J Neurosci. 2009 Jun 17;29(24):7788-96
Fulltext: http://www.jneurosci.org/cgi/content/full/29/24/7788

Hierarchical stimuli (large shapes composed of small shapes) have long been used to study how humans perceive the global and the local content of a scene--the forest and the trees. Studies using these stimuli have revealed a global advantage effect: humans consistently report global shape faster than local shape. The neuronal underpinnings of this effect remain unclear. Here we demonstrate a correlate and possible mechanism in monkey inferotemporal cortex (IT). Inferotemporal neurons signal the global content of a hierarchical display approximately 30 ms before they signal its local content. This is a specific expression of a general principle, related to spatial scale or spatial frequency rather than to hierarchical level, whereby the representation of a large shape develops in IT before that of a small shape. These findings provide support for a coarse-to-fine model of visual scene representation.

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