One thing humans, and in fact all primates can do with remarkable ease compared to computers is face recognition, especially across a range of viewing conditions. At her lab at Caltech, Doris Tsao tries to explore the way the brain does this. In her recent Science paper, she explored view invariance in the recently discovered face-processing network of the macaque monkey. Of the six interconnected face-selective regions, They recorded from the two middle patches (ML, middle lateral, and MF, middle fundus) and two anterior patches (AL, anterior lateral, and AM, anterior medial) while showing images of faces subject to accidental image transformations like changes in view direction. They found that the anatomical position of a face patch was associated with a unique functional identity: Face patches differed qualitatively in how they represented identity across head orientations. Neurons in ML and MF were view-specific; neurons in AL were tuned to identity mirror-symetrically across views, thus achieving partial view invariance; and neurons in AM, the most anterior face patch, achieved almost full view invariance.
Here they demonstrate the view dependence of ML/MF and AL and the view independence of AM by showing the separability in MDS space. Since all the views are overlapping in plot C, the responses to images of each viewpoint are indistinguishable indicating that AM is viewpoint invariant. They quantify this in G and H using sharpness of identity tuning half-widths and head orientation tuning depths. Interestingly, the time course of the view invariant response of AM is significantly longer than that of ML/MF and AL. This indicates that the view invariance is a consequence of a much more complex network structure than simple feed forward connections.
Join us on Tuesday April 30th, 2013 at 4pm in the CNCB large conference room to hear more from Dr. Doris Tsao about how her group has demonstrated view invariance in the hierarchy of the facial recognition system in macaques.
Marvin Thielk is a first-year student in the UCSD Neuroscience program. He is currently rotating in the Sharpee lab.
Freiwald W.A. & Tsao D.Y. (2010). Functional Compartmentalization and Viewpoint Generalization Within the Macaque Face-Processing System, Science, 330 (6005) 845-851. DOI: 10.1126/science.1194908