International Meeting for Autism Research (May 7 - 9, 2009): Diffusion Tractography of Frontal and Temporal Lobe Pathways to the Amygdala in Adolescents with Autism Spectrum Disorders

Thursday, May 7, 2009

Northwest Hall (Chicago Hilton)

10:00 AM

M. Carrasco , Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI

J. L. Wiggins , Department of Psychology, University of Michigan, Ann Arbor, MI

S. J. Weng , Department of Psychology, University of Michigan, Ann Arbor, MI

S. Peltier , Biomedical Engineering and Functional MRI Laboratory, University of Michigan, Ann Arbor, MI

S. Perkins , Child And Adolescent Psychiatry, University of Michigan, Ann Arbor, MI

K. Fitzgerald , Child And Adolescent Psychiatry, University of Michigan, Ann Arbor, MI

C. Lord , University of Michigan Autism & Communication Disorders Centers, University of Michigan, New York, NY

C. S. Monk , Department of Psychology, University of Michigan, Ann Arbor, MI

Background: Research has shown that the amygdala plays a central role in the socioemotional processing of faces. Differences in anatomical connectivity between the amygdala and brain structures involved in face and emotional perception may be responsible for some of the social deficits encountered among individuals with Autism Spectrum Disorders (ASD). Studies focusing on anatomical connectivity in ASD between the amygdala and its frontal and temporal projections have been limited; our study will aim to address this gap in the literature.

Objectives: We used diffusion tensor imaging (DTI) to estimate regional white matter properties in ASD and typically developing participants. Group differences were assessed in the projections between the amygdala and the medial frontal/orbitofrontal cortices, and the amygdala and medial temporal cortex structures.

Methods: Our preliminary sample includes 7 ASD and 10 controls; final analyses will be performed once 15 ASD and 15 controls have been recruited. ASD and control subjects were equivalent for IQ, age (range 11-17), sex, and manual preference. In addition, ASD adolescents were diagnosed using the ADOS and ADI-R and the diagnosis was confirmed by clinical consensus. For diffusion tensor image analysis, a diffusion weighted single-shot spin echo-planer imaging (DWSSEPI) sequence acquired 34 axial slices to cover the regions of interest, with a TE/TR of 90/6500 ms, a matrix of 128x128, an FOV of 220 mm, a slice thickness of 2.5 mm, and 6 averages. Diffusion weighting was applied in 12 directions with a b-value of 1000 s/mm2. The diffusion tensor was calculated for each voxel, and averaged diffusion coefficient (ADC) and the fractional anisotropy (FA) maps were generated. After transformation to a common anatomical space, fractional anisotropy image values were used as measures in a two-way ANOVA.

Results: Preliminary results show group differences in fractional anisotropy (FA) within the left amygdala. FA values were higher in adolescents with ASD relative to controls (MNI coordinates at center of cluster: x = -19, y = -4, z = -24; cluster 91; t value = 6.57). Tractography analyses will focus on group differences in amygdala projections to the medial frontal/orbitofrontal cortices and to neighboring medial temporal structures.

Conclusions: Preliminary results show group differences in white matter properties within the left amygdala. Upcoming tractography analyses will yield additional information on the anatomical connections between the amygdala and frontal/temporal structures involved in socioemotional face processing in ASD adolescents.

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