Friday, February 03, 2006

The "Face Module" Identified in Moneys?

Oooh... aah... besides the general concept of such a specialized module, it's hard for The Neurocritic to find fault with this one:

A Cortical Region Consisting Entirely of Face-Selective Cells
Doris Y. Tsao, Winrich A. Freiwald, Roger B. H. Tootell, Margaret S. Livingstone
Science 3 February 2006: Vol. 311. no. 5761, pp. 670-674

Face perception is a skill crucial to primates. In both humans and macaque monkeys, functional magnetic resonance imaging (fMRI) reveals a system of cortical regions that show increased blood flow when the subject views images of faces, compared with images of objects. However, the stimulus selectivity of single neurons within these fMRI-identified regions has not been studied. We used fMRI to identify and target the largest face-selective region in two macaques for single-unit recording. Almost all (97%) of the visually responsive neurons in this region were strongly face selective, indicating that a dedicated cortical area exists to support face processing in the macaque.

Using fMRI, the authors identified a face-specific area homologous to the human fusiform face area (FFA) in two macaque monkeys. Then they recorded from single neurons in this ~16mm2 region along the superior temporal sulcus.

[NOTE: of course, face-selective cells were identified in primate temporal cortex by Rolls, Gross, Perrett, etc. well before the advent of fMRI and discovery of the human FFA... but I digress.]

They tested the face selectivity of 405 neurons by presenting pictures of items from different categories (faces, bodies, fruits, gadgets, hands, and scrambled patterns). About 80% of the neurons were classified as visually responsive. In 97% of the neurons (i.e., all but 8 out of the 310 visually responsive cells), responses to faces were at least 2 times greater than responses to pictures from other categories.

SUMMARY from The Neurocritic: Now all they have to do is to lesion this face-selective region and then see what happens to the monkeys' face recognition abilities. Are there enough other "face selective" neurons distributed elsewhere in the temporal lobe to support face recognition?

ADDENDUM and Disclaimer: The Neurocritic is not necessarily endorsing animal research by posing that rhetorical question.

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