Autism and agenesis of the corpus callosum (AgCC) are distinct conditions – the first is behavioral while the second anatomical. Yet about 40% of people born with AgCC show clear indications of autism. Diffusion tractography is a 3D rendering technique that uses data from diffusion tensor imaging (DTI), to map out cortical connections. DTI is basically a refinement of standard MRI which can additionally measure the diffusion of water within tracts of axons. A collaborative effort at UCSF and Berkeley has now analyzed the tractography data for an AgCC study group using network mapping techniques borrowed from mathmatics. Their results now add much needed rigor to previous efforts to structurally define behavior.
Prior imaging studies of Kim Peek (1951-2009), a.k.a. the Rain Main, firmly established the casual association of AgCC to autism. When the midline parts of the brain fail to develop, as happens in AgCC, the axons which normally would travel to the opposite hemisphere will seek out new targets closer to home. The California researchers asked the following simple question: is the lack of inter-hemispheric connectivity consistently associated with unique intra-hemispheric connections? Indeed they found that it is.