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Abstract

We demonstrated that, when human subjects have to classify human/monkey morphed faces that change along a continuum, they draw the category boundary closer to their own species (at approximately 60 human/40 monkey). Considering that neurons in the infero-temporal (IT) cortex encode face information, we recorded the single-unit activity (SUA) of 118 neurons and the local field potential (LFP) at 58 sites of the IT cortex of one macaque monkey during fixation of morphed faces. Out of 118 single units, 85 were visually responsive and 23 were face cells according to standard criteria. We used a two-class (human - monkey) classifier (k-NearestNeighbor) to analyze the population activity of visually responsive units and all LFPs. Symmetric to the findings in humans, the classifier drew the category boundary closer to the monkey category (at approximately 40 human/60 monkey) for both kinds of neural signals. These results suggest an ‘own-species‘ advantage in the encod
ing of face stimuli. Our findings also indicate that a large fraction of IT neurons participate in the encoding of face categories.