Seminar: 1/18 - Clarifying the functional neuro-anatomy of face processing by combining lesion studies and neuroimaging
11:00 to 12:30 PM at:
University of Louvain, Belgium
Understanding the functional neuro-anatomy of face processing in the human brain is a long-standing goal of Cognitive Neuroscience. Up to the early 90's, the most important source of knowledge was from lesion studies, i.e. making correlations between the localization of lesions in groups of brain-damaged patients and their face recognition impairments. The influence of the cognitive approach in Neuropsychology, with an emphasis on single-case functional investigations, as well as the advent of neuroimaging studies in the healthy brain, have considerably reduced the importance of lesion studies in clarifying the neuro-anatomical aspects of face processing. In this talk, my goal will be to illustrate how neuroimaging investigations of single-cases of acquired prosopagnosic patients can still greatly increase our knowledge in this field. Neuroimaging studies of the normal brain have shown that the middle fusiform gyrus ('FFA') and the inferior occipital gyrus ('OFA') are activated by both detection and identification of faces. Among other observations, our studies of the patient PS, a case of prosopagnosia with normal object recognition, show that the right 'FFA' can be recruited to detect faces independently of the 'OFA' of the same hemisphere (Rossion et al., 2003). However, fMRI-adaptation investigations suggest that both areas are necessary to perform individual discrimination of faces (Schiltz et al., 2006). Recent observations also show that the the same brain area, here the right 'FFA', may be impaired at individual face discrimination while performing normal individual object discrimination. This suggests that clusters of neurons coding specifically for different categories in this area (Grill-Spector et al., 2006) can be functionnally independent. Finally, when structurally intact, non-face preferring areas such as the ventral part of the lateral occipital complex (vLOC) may subtend residual individual discrimination of faces following prosopagnosia. Altogether, these studies show that faces are processed through multiple pathways in the human brain, with a subset of these areas responding preferentially to faces being critical for efficient face recognition.
Rossion, B., Caldara, R., Seghier, M., Schuller, A.-M., Lazeyras, F., Mayer, E. (2003). A network of occipito-temporal face-sensitive areas besides the right middle fusiform gyrus is necessary for normal face processing. Brain, 126, 2381-2395.
Schiltz C, Sorger B, Caldara R, Ahmed F, Mayer E, Goebel R, Rossion B. (2006). Impaired Face Discrimination in Acquired Prosopagnosia Is Associated with Abnormal Response to Individual Faces in the Right Middle Fusiform Gyrus. Cerebral Cortex, 16, 574-586.
Sorger, B., Goebel, R., Schiltz, C., Rossion, B. (2007). Understanding the functional neuroanatomy of prosopagnosia. NeuroImage, 35, 836-852.