Brain Differences in Autism 2: Fusiform Gyrus

A review of: van Kooten, I.A., Palmen, S.J., von Cappeln, P., Steinbusch, H.W., Korr, H., Heinsen, H., Hof, P.R., van Engeland, H., Schmitz, C. (2008). Neurons in the fusiform gyrus are fewer and smaller in autism. Brain DOI: 10.1093/brain/awn033

The fusiform gyrus is an area of the temporal lobes of the brain that has been extensively associated to people’s ability to recognize faces. The authors of this paper proposed that abnormalities in the fusiform gyrus may explain some social deficits in Autism. Although people with autism can correctly complete face processing tasks, the authors noted that people with autism display reduced activation of the fusiform gyrus during these tasks. This alteration could be responsible for atypical behaviors such as reduced eye contact. To examine the underlying hypothesis further, the authors examined the post-mortem brains of 7 children and adults with autism as compared to 10 matched controls. They found significantly reduced neuron density and total neuron number in areas of the fusiform gyrus but not in other cortical areas. The authors presented a very interesting alternative interpretation. Although the reduced neural density and number in the fusiform gyrus could reflect neurodevelopmental impairments in the fusiform itself resulting in specific functional impairments, it is also possible that this atrophy is related to ‘loss of targets’ to which the fusiform gyrus projects. That is, the fusiform gyrus sends neural projections to the amygdale, which play an important role in monitoring eye gaze and other social behaviors. Thus, is the finding of reduced neural density and total number of the fusiform gyrus a reflection of dysfunction of this area of the brain, or simply a byproduct of alterations in other related areas such as the amygdale?