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Abnormalities of Brain Structure and Function Underlying the Distribution of Visual Attention in Autism

出版	University of California, San Diego and San Diego State University, 1992
URL	http://books.google.com.hk/books?id=qvEHqO80mZwC&hl=&source=gbs_api

註釋Autism is a developmental disorder in which there is profound disruption of cognitive and social function, with critical deficits in attentional operations. Increased understanding of the relationships among the structural and functional abnormalities underlying specific behavioral problems makes this disorder an appropriate model for the study of attentional systems. Autopsy and brain imaging studies have consistently identified bilateral abnormalities of posterior cerebellar vermis and hemispheres in autism. In some patients there is additional or corollary bilateral damage to parietal cortex and hippocampus, but the primary brain pathology in autism involves the posterior cerebellum. Several recent studies have linked the cerebellum to cognitive deficits. For example, patients with focal lesions of the cerebellum as well as those with autism are quite slow to shift attention between auditory and visual modalities. Here, in a series of spatial attention tasks patterned after those developed by Michael Posner, autistic individuals exhibited deficits that suggest involvement of the cerebellum and parietal cortex in attention-related visual processing. First, autistic subjects and children with acquired unilateral cerebellar lesions had extremely delayed responses to simple visual targets presented at a pre-cued location, but only when the interval between cue and target was short (100 ms). With longer cue-to-target delays their response times were as fast as those of normal control subjects. These results imply that the cerebellum plays an important role in the rapid orienting of attention. Second, a subgroup of autistic subjects found to have parietal abnormalities on magnetic resonance images, showed behavioral deficits similar to those that have been reported for patients with lesions of parietal cortex. The autistic subjects were extremely slow to respond to visual targets on either the right or left when their attention had been directed to the opposite side. Performance deficits were highly correlated with quantitative estimates of parietal abnormality. This group of autistic subjects also produced electrophysiological patterns consistent with excessively narrowed spatial processing. Results from these studies provide structural, behavioral and physiological evidence of parietal abnormality in a subgroup of autistic people. This brain pathology may be responsible for an excessively restricted focus of attention.