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Abstract:
We investigate to which extent signals recorded from the inferior temporal (IT) cortex of two macaque monkeys can discriminate between (i) faces vs objects, and (ii) monkey vs human faces. During a fixation task, we simultaneously recorded the local field potential (LFP) and spiking activity of single cells at 202 different sites. On each site we computed (i) visual-evoked potentials (VEP), (ii) single-trial-based instantaneous power and phase for different frequency bands, and (iii) spiking activity of single neurons. Considering the VEPs, specifically the P100 deflection, we found that its onset latency occurred earlier for faces than for objects ( p < 0.01) and for monkey than for human faces ( p < 0.05). In contrast, the P100 amplitude did not systematically differentiate between these categories. In the frequency domain, we found that the amount of phase-locking (across trials in single electrodes) of the theta-band around the P100 discriminated between faces/objects and humans/monkeys. Finally, we found that differences in the amount of phase-locking of the gamma-band around P100 between faces/objects were significantly correlated with faces/objects selectivity of single neurons at those locations. Our findings provide novel insights into the neural mechanisms of object and face recognition.
