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Abstract:
Face perception is one of the most crucial abilities for social animals like humans and nonhuman primates. fMRI-, lesion- and electrophysiology studies in humans and monkeys have indicated the existence of a dedicated and wide-spread face-processing network. In humans the most robust face-selective brain areas are fusiform face area (FFA), occipital face area (OFA) and superior temporal sulcus (STS). However, in monkeys the strongest face selectivity is found predominantly in STS, and no reliable face selectivity has been reported in fusiform gyrus and occipital temporal region. These differences may be a species difference, or they may be due to technical difficulties, because in monkeys the fusiform gyrus and ventral occipital-temporal area are located in regions that are difficult to map with fMRI due to susceptibility artifacts from the ear canal. Here we used an optimized imaging protocol at 7T, which does not suffer from the usual signal loss in inferior temporal areas. We investigated the functional organization of face processing in 5 awake or anesthetized macaques while the subjects viewed faces, fruit, houses and fractal patterns.
We found face-specific BOLD responses in STS, anterior medial temporal sulcus (AMTS), the regions anterior and lateral to AMTS and amygdala, consistent with previous fMRI and electrophysiology results. But in addition, entorhinal cortex (EC), ventral TE (posterior to AMTS), and hippocampus also contain face selective patches. These areas have not been reported to be face-selective in monkeys before, although they were shown to be responsive to faces with fMRI or intracortical recording in humans. The results indicate that there is much more extensive face selective brain activity than earlier studies have found in monkey ventral temporal lobe and suggests a large degree of similarity between the human and monkey face-processing network.
