A new publication in the journal Brain describes a significant anatomical difference in the face processing area of brain donors with autism compared to non-affected donors. Research in the 1990s indicated that individuals with autism spectrum disorders had abnormalities in face perception, leading researchers to investigate a unique cortical brain
area found in primates, referred to as the face processing area. Cells in this area are activated selectively in response to faces as opposed to non-face objects (e.g. a chair). Using non-invasive imaging technology for the study of human subjects, several labs demonstrated that there was less activation of the face processing area in those diagnosed with autism, and that these changes in face processing might contribute to the social deficits seen in those with autism.
This paper describes a microscopic evaluation of the face processing area, located in a brain region called the fusiform gyrus. For the last five years, Imke van Kooten, Ph.D., and her colleagues at the University of Maastricht in the Netherlands and here in the U.S. have made painstaking measurements of neurons in post mortem brain sections. Variations in neuronal arrangement allows for the identification of boundaries between different cortical regions. Statistical deviations in size or total number of neurons is thought to reflect a change in function in a given area. This report compares the neuron density, total neuron number and mean cell body volume in the fusiform gyrus with that of the primary visual cortex -- an area also dedicated to vision, located in the back of the brain.
Neurons in the primary visual cortex connect to neurons in the fusiform gyrus, effectively sending visual information to the region specialized for face processing. Analysis of neurons in the layers of these two areas showed that, compared to controls, patients with autism showed significant reductions in neuron density, total neuron numbers, and mean neuron cell volume in the fusiform gyrus. These results are interpreted to mean that, in autism, while the primary visual cortex has neurons in normal numbers and size, the fusiform gyrus shows neuropathological changes.
The authors suggest that the reduced neuronal size and total neuron number in the fusiform gyrus might contribute to impaired face processing in autism. Since individuals with autism can indeed 'see' faces, most likely by utilization of unique neural circuitry, the research team plans further study of other additional cortical areas implicated in visual processing. This continued research will be part of the Brain Atlas Project, a larger study supported by Autism Speaks' Autism Tissue Program. The project, a joint effort of co-PIs Christoph Schmitz, Ph.D., and Jerzy Wegiel, Ph.D., at the NY Institute for Basic Research in Staten Island, was started officially in 2002 and is comprised of 14 autism-affected and 14 non-affected brain donor hemispheres ranging from age 4 to 66. The publication summarized here represents the first data from this project, reporting on the first 7 autism-affected brains. The aim is to perform comprehensive cell counting and volumetry, neuropathology, MRI and 3-D reconstructions of donor brain hemispheres, a rare and unique resource so lovingly provided by families.
Autism Speaks' Autism Tissue Program supports specialized neuropathology research such as this by providing approved scientists access to the most rare and necessary of resources, post mortem human brain tissue. We wish to recognize the gifts of hope by our ATP brain donor families.
More information can be found at www.autismtissueprogram.org or call (877) 333-0999 for information or to initiate a brain donation.
Van Kooten, IAJ, Palmen, SJMC, von Cappeln, P; Steinbusch, HWM, Korr, H, Heinsen, H, Hof, PR, van Engeland, H & C Schmitz. 2008. Neurons in the fusiform gyrus are fewer and smaller in autism. Brain, 131(4):987-999.