Event-related brain response abnormalities in autism: evidence for impaired cerebello-frontal spatial attention networks

Although under some conditions the attention-related late positive event-re lated potential (ERP) response (LPC) is apparently normal in autism during visual processing, the LPC elicited by visuospatial processing may be compr omised. Results from this study provide evidence for abnormalities in autis m in two components of the LPC generated during spatial processing. The ear ly frontal distribution of the LPC which may reflect attention orienting wa s delayed or missing in autistic subjects during conditions in which attent ion was to peripheral visual fields. The later parietal distribution of the LPC which may be associated with context updating was smaller in amplitude in autistic subjects regardless of attention location. Both abnormalities suggest disruption of function in spatial attention networks in autism. Evi dence that the cerebellar abnormalities in autism may underlie these defici ts comes fr om: (I) similar results in ERP responses and spatial attention deficits in patients with cerebellar lesions; (2) brain-behavior correlatio ns in normally functioning individuals associating the size of the posterio r cerebellar vermis and the latency of the frontal LPC; and (3) a previousl y reported complementary correlation between the size of the posterior verm al lobules and spatial orienting speed. Although the scalp-recorded LPC is thought to be cortically generated, it may be modulated by subcortical neur al activity. The cerebellum may serve as a modulating influence by affectin g the task-related antecedent attentional process. The electrophysiological abnormalities reported here index spatial attention deficits in autism tha t may reflect cerebellar influence on both frontal and parietal spatial att ention function. (C) 2001 Elsevier Science B.V. All rights reserved.