The cortical face network of the prosopagnosic patient PS with fast periodic stimulation in fMRI.

Following brain damage, the patient PS suffers from selective impairment in recognizing individuals by their faces, i.e., prosopagnosia. Her case has been documented in more than 30 publications to date, informing about the nature of individual face recognition and its neural basis. Here we report new functional neuroimaging data obtained on PS with a recently developed fast periodic stimulation functional imaging (FPS-fMRI) paradigm combining high sensitivity, specificity and reliability in identifying the cortical face-selective network (Gao et al., 2018). We define the extent of the large and reliable face-selective activation in the lateral section of the right middle fusiform gyrus, i.e., right FFA, which forms a single cluster of activation lying at the anterior border of the patient's main lesion in the inferior occipital gyrus. The contribution of posterior face-selective responses in the right or left inferior occipital gyrus is ruled out, strongly supporting the view that face-selective activity emerges in the right middle fusiform gyrus of the patient's brain from non-face-selective inputs from early visual areas. Despite this, low-level visual cues, i.e., amplitude spectrum of images, do not contribute to neural face-selective responses anywhere in the patient's cortical face network. This sensitive face-localizer approach also reveals an intact face-selective network anterior to the fusiform gyrus, including clusters in the ventral anterior temporal lobe (occipito-temporal sulcus and temporal pole) and the inferior frontal gyrus, with a right hemispheric dominance. Overall, with the exception of the left inferior occipital gyrus, the cortical face network of the prosopagnosic patient PS appears remarkably similar to typical individuals in non-brain damaged regions. However, unlike in neurotypical adults tested in the present study, including age-matched controls, a novel paradigm based on FPS-FMRI confirms that the patient's face network is insensitive to differences between rapidly presented pictures of unfamiliar individual faces, in line with her prosopagnosia.