The neuroanatomy of pictorial reasoning in autism

Individuals with autism present with a constellation of social, behavioral, and cognitive symptoms. A striking characteristic is the contrast between their language and visual processing abilities. The work in this thesis combines behavioral, functional MRI, and diffusion tensor imaging methods to examine the neurobiological basis of the discrepancy between linguistic and visuospatial skills in autistic cognition. A pictorial reasoning task, designed to manipulate the degree to which language vs. visuospatial abilities may be differentially engaged in solving picture puzzles, was administered under three conditions: visuospatial, semantic and a hybrid visuospatial-cum-semantic condition. Whereas participants with Asperger's syndrome and typically developing controls (CTRL) were found to exhibit similar performance profiles, high-functioning individuals with autism (HFA) differed from these two groups: they were least efficient on the semantic condition and appeared to benefit from and favor the use of visuospatial mediation in problem solving. Results from functional MRI revealed a pattern of decreased activation in fronto-temporal language areas, and an increased reliance on posterior brain regions in the parietal and ventral temporal lobes in HFA, supporting the earlier behavioral findings. Specifically, the inferior frontal gyrus appeared to play an important role in verbal mediation and semantic integration in CTRL, whereas HFA relied more extensively on inferior and ventral regions of the temporal lobe, in keeping with a cognitive preference for visual strategies.

Department dc:contributor.department

Harvard University--MIT Division of Health Sciences and Technology.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Sahyoun, Chérif P

Advisor dc:contributor.advisor

• Maria Mody.

• Harvard University--MIT Division of Health Sciences and Technology.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/54589

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/54589