Investigation on white matter integrity in autism with diffusion-weighted magnetic resonance imaging

Patients with a diagnosis of autism spectrum disorder display deficits in
social interaction and language production, as well as in other highly
integrative cognitive functions, reflected in stereotyped and repetitive
behaviours. In recent years it has been proposed that these symptoms could be
due to an imbalance of the ratio between short and long range information
transfer and processing in the brain. New techniques to analyze
diffusion-weighted magnetic resonance (DW-MRI) images can now be used to
examine structural integrity parameters of specific white matter fiber bundles
in the brain, as well as to recover probabilistic maps of the anatomical
connectivity of specific brain regions. These tools are therefore suitable to
test the underconnectiv-ity/overconnectivity hypothesis which has been advanced
for autism spectrum disorder.

We aim at performing a thorough analysis of structural and hodological (i.e.
connectional) properties of white matter in autistic patients, at the level of
resolution allowed by diffusion-weighted MR images. This will include an
analysis of integrity pa-rameters at the level of the single voxel and in
specific fibre bundles. We will then per-form whole-brain tractography to
quantify differences between healthy individuals and autistic patients in the
ratio of long- and short-range anatomical connections as a function of the
distance. We will also use the results from tractography to evaluate
differ-ences in connectivity-based cortical parcellation. Our theoretical goal
is to determine what kind of evidence can be found by means of DW-MRI which can
be predicted by the underconnectivity/overconnectivity hypothesis.

For this study we will use diffusion-weighted and other structural (T1 and
T2-weighted) and default-mode functional (EPI T2*-weighted) magnetic resonance
images, as well as several behavioral parameters. The subject will not be
required to perform any task inside the scanner.

The experiments will not entail more than minimal risk to the participants. The
study is not intended to benefit the subjects directly. However, the data
collected during this study could improve our understanding of autism and human
cognition at large. In particular, this investigation could help us clarify why
autistic individuals are unable to recognize the state of mind of someone else.