The effect of face inversion for neurons inside and outside fMRI-defined face-selective cortical regions.

J Neurophysiol. 2014 Dec 17;:jn.00700.2014

Authors: Taubert J, Van Belle G, Vanduffel W, Rossion B, Vogels R

Abstract
It is widely believed that face processing in the primate brain occurs in a network of category-selective cortical regions. Combined fMRI-single cell recording studies in macaques have identified high concentrations of neurons that respond more to faces than objects within face-selective patches. However, cells with a preference for faces over objects are also found scattered throughout inferior temporal (IT) cortex, raising the question whether face-selective cells inside and outside the face patches differ functionally. Here we compare the properties of face-selective cells inside and outside face-selective patches in the IT cortex by means of an image manipulation which reliably disrupts behavior towards face processing: inversion. We recorded IT neurons from two fMRI-defined face-patches (ML and AL) and a region outside the face patches (herein labeled OUT) during upright and inverted face stimulation. Overall, turning faces upside down reduced the firing rate of face-selective cells. However, there were differences among the recording regions. First, the reduced neuronal response for inverted faces was independent of stimulus position, relative to fixation, in the face-selective patches (ML and AL) only. Additionally, the effect of inversion for face-selective cells in ML, but not those in AL or OUT, was impervious to whether the neurons were initially searched for using upright or inverted stimuli. Collectively, these results show that face-selective cells differ in their functional characteristics depending on their anatomico-functional location, suggesting that upright faces are preferably coded by face-selective cells inside but not outside the fMRI-defined face-selective regions of the posterior IT cortex.

PMID: 25520434 [PubMed - as supplied by publisher]