invariant visual representation by single neurons in the human brain

We here ask whether MTL neurons can represent high-level information in an abstract manner characterized by invariance to the metric characteristics of the images. This suggested that neurons might encode an abstract representation of an individ- ual.

Another unit (from a different patient) responded only to images of The Beatles, another one to cartoons from The Simpson’s television series and another one to pictures of the basketball player Michael Jordan. For example, in one case, a unit responded only to three completely different images of the ex-president Bill Clinton. An unpublished observation in our previous recordings was the sometimes surprising degree of invariance inherent in the neuron’s (that is, unit’s) ﬁring behaviour. Stimuli were different pictures of individuals, animals, objects and landmark buildings presented for 1 s in pseudo- random order, six times each. We analysed responses of neurons from the hippocampus, amygdala, entorhinal cortex and parahippocampal gyrus to images shown on a laptop computer in 21 recording sessions.

For each patient, the placement of the depth electrodes, in combination with micro-wires, was deter- mined exclusively by clinical criteria 13. The subjects were eight patients with pharmacologically intract- able epilepsy who had been implanted with depth electrodes to localize the focus of seizure onset. 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. 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. We have previously shown that neurons in the human medial temporal lobe (MTL) ﬁre selectively to images of faces, animals, objects or scenes 13,14.

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 angle 2,4,7–12. How such a robust, high-level representation is achieved by neurons in the human brain is still unclear 1–6. Fried 2,4 It takes a fraction of a second to recognize a person or an object even when seen under strikingly different conditions. Invariant visual representation by single neurons in the human brain R.