The Occipital Face Area is a region of the human brain. It is responsible for identifying parts of faces, such as eyes, nose, and mouth.
Function
It is the least understood face-selective region within the brain and is implicated in the network responsible for the ability to recognize faces, the Ventral Occipital Temporal system. The OFA acts as the first stage in a distributed, hierarchical network for face computations of increasing complexity, such as face identification and discrimination of facial expressions - which are performed at higher levels of the cortex. Studies using high temporal resolution demonstrated that the OFA is able to process face information approximately 100 milliseconds after the onset of the stimulus, making it the first face-selective cortical region to respond to facial stimuli. Neuropsychological studies of patients with acquired prosopagnosia and transcranial magnetic stimulation studies of healthy participants show that the OFA is functionally necessary for some face computations. They also suggest the existence of connections between the early visual cortex and the fusiform face area that bypass the OFA. However, the OFA remains an essential part of the face perception network and represents face parts prior to further processing of more complex facial features in higher face-selective cortical regions. The OFA is frequently found within the right hemisphere, located on the lateral surface of the occipital lobe either in or around the inferior occipital gyrus. The location of the OFA varies spatially between people. Group peak Talairach coordinates place the OFA in Brodmann area 18 or 19.
Research
Patient P.S.
Examining case studies of individuals with OFA lesions provides more insight into its function. Prosopagnosic patients have been essential for this initiative, especially patient P.S., a right handed woman with a lesion extending from the posterior part of the right inferior occipital gyrus into the posterior fusiform gyrus. This lesion left patient P.S. without a right OFA and she exhibited great difficulty with facial recognition in daily life. Additionally, she had trouble with facial gender discrimination and could not match unfamiliar faces seen from different viewing angles. Despite the extensive cortical damage she suffered, patient P.S. exhibited a normal right fusiform face area when compared to age matched controls using a standard fMRI localizer. She was unimpaired with basic-level and within-class object discrimination and recognition tasks. Results like these demonstrate that face information can still be processed in the right FFA despite the absence of the right OFA, thus suggesting the presence of alternate cortical routes between the early visual cortex and fusiform gyrus.
