Journal of Animal Science, Vol 69, Issue 12 5008-5016, Copyright © 1991 by American Society of Animal Science

JOURNAL ARTICLE

How the sheep's brain controls the visual recognition of animals and humans

K. M. Kendrick
Agricultural and Food Research Council, Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, UK.

Visual recognition of objects and individuals is important for humans and many animal species. How does the brain process such visual information and how does experience modify such processing? To answer these questions we have used single-cell, electrophysiological recording techniques to investigate the responses of single neurons in the temporal cortex of the brain of the conscious sheep to visual images of animals and humans. Results show that a small population of these cells responds (latencies less than 180 ms) specifically to projected images of animal and human faces. Different cells respond to 1) faces with horns, and how large the horns are; 2) faces of sheep of the same breed, particularly to socially familiar individuals, and 3) faces of humans or dogs. In general, frontal views of faces (i.e., direct eye contact) are more effective stimuli than profiles or views of the back of the head. Some other cells in the temporal cortex respond to the sight of a human shape, rather than to the face. These latter cells are specialized for visual recognition of the human shape dependent on what actions are displayed (approaching or withdrawing figure), posture adopted (bipedal or quadrupedal), and view presented (front or side). These results provide important information on the complex neural processing of visual recognition of individuals by sheep and suggest that experience may modify sensory processing. Thus, behaviorally important, distinguishing features (such as horns), preferred individuals (socially familiar animals), and potentially threatening individuals (humans and sheep dogs) are specifically coded for, at a sensory level, so that appropriate behavioral or emotional responses can be made with the minimum delay.