Cell
Volume 169, Issue 6, 1 June 2017, Pages 1013-1028.e14
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Article
The Code for Facial Identity in the Primate Brain

https://doi.org/10.1016/j.cell.2017.05.011Get rights and content
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Highlights

  • Facial images can be linearly reconstructed using responses of ∼200 face cells

  • Face cells display flat tuning along dimensions orthogonal to the axis being coded

  • The axis model is more efficient, robust, and flexible than the exemplar model

  • Face patches ML/MF and AM carry complementary information about faces

Summary

Primates recognize complex objects such as faces with remarkable speed and reliability. Here, we reveal the brain’s code for facial identity. Experiments in macaques demonstrate an extraordinarily simple transformation between faces and responses of cells in face patches. By formatting faces as points in a high-dimensional linear space, we discovered that each face cell’s firing rate is proportional to the projection of an incoming face stimulus onto a single axis in this space, allowing a face cell ensemble to encode the location of any face in the space. Using this code, we could precisely decode faces from neural population responses and predict neural firing rates to faces. Furthermore, this code disavows the long-standing assumption that face cells encode specific facial identities, confirmed by engineering faces with drastically different appearance that elicited identical responses in single face cells. Our work suggests that other objects could be encoded by analogous metric coordinate systems.

Keywords

inferior temporal cortex
primate vision
face processing
decoding
electrophysiology

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