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Invariant visual representation by single neurons in the human brain


It takes a fraction of a second to recognize a person or an object even when seen under strikingly different conditions. How such a robust, high-level representation is achieved by neurons in the human brain is still unclear1,2,3,4,5,6. In monkeys, neurons in the upper stages of the ventral visual pathway respond to complex images such as faces and objects and show some degree of invariance to metric properties such as the stimulus size, position and viewing angle2,4,7,8,9,10,11,12. We have previously shown that neurons in the human medial temporal lobe (MTL) fire selectively to images of faces, animals, objects or scenes13,14. Here we report on a remarkable subset of MTL neurons that are selectively activated by strikingly different pictures of given individuals, landmarks or objects and in some cases even by letter strings with their names. These results suggest an invariant, sparse and explicit code, which might be important in the transformation of complex visual percepts into long-term and more abstract memories.

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Figure 1: A single unit in the left posterior hippocampus activated exclusively by different views of the actress Jennifer Aniston.
Figure 2: A single unit in the right anterior hippocampus that responds to pictures of the actress Halle Berry (conventions as in Fig. 1).
Figure 3: A multi-unit in the left anterior hippocampus that responds to photographs of the Sydney Opera House and the Baha'i Temple (conventions as in Fig. 1).
Figure 4: Distribution of the area under the ROC curves for the 51 units (out of 132 responsive units) showing an invariant representation.

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We thank all patients for their participation; P. Sinha for drawing some faces; colleagues for providing pictures; I. Wainwright for administrative assistance; and E. Behnke, T. Fields, E. Ho, E. Isham, A. Kraskov, P. Steinmetz, I. Viskontas and C. Wilson for technical assistance. This work was supported by grants from the NINDS, NIMH, NSF, DARPA, the Office of Naval Research, the W.M. Keck Foundation Fund for Discovery in Basic Medical Research, a Whiteman fellowship (to G.K.), the Gordon Moore Foundation, the Sloan Foundation, and the Swartz Foundation for Computational Neuroscience.

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Correspondence to R. Quian Quiroga.

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This contains Supplementary Methods and Legends to accompany Supplementary Figures S1-11. (PDF 4435 kb)

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Quiroga, R., Reddy, L., Kreiman, G. et al. Invariant visual representation by single neurons in the human brain. Nature 435, 1102–1107 (2005).

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