Authors
Minshew NJ. Luna B. Sweeney JA.
Institution
Department of Psychiatry, University of Pittsburgh School of Medicine,
PA 15213, USA.
Title
Oculomotor evidence for neocortical systems but not cerebellar dysfunction
in autism. [see comments.].
Comments
Comment in: Neurology. 1999 Mar 23;52(5):902-4 ; 10102402, Comment in:
Neurology. 2000 Jan 11;54(1):269-70 ; 10636173
Source
Neurology. 52(5):917-22, 1999 Mar 23.
Abstract
OBJECTIVE: To investigate the functional integrity of cerebellar and
frontal systems in autism using oculomotor paradigms. BACKGROUND: Cerebellar
and neocortical systems models of autism have been proposed. Courchesne
and colleagues have argued that cognitive deficits such as shifting attention
disturbances result from dysfunction of vermal lobules VI and VII. Such
a vermal deficit should be associated with dysmetric saccadic eye movements
because of the major role these areas play in guiding the motor precision
of saccades. In contrast, neocortical models of autism predict intact saccade
metrics, but impairments on tasks requiring the higher cognitive control
of saccades. METHODS: A total of 26 rigorously diagnosed nonmentally retarded
autistic subjects and 26 matched healthy control subjects were assessed
with a visually guided saccade task and two volitional saccade tasks, the
oculomotor delayed-response task and the antisaccade task. RESULTS: Metrics
and dynamics of the visually guided saccades were normal in autistic subjects,
documenting the absence of disturbances in cerebellar vermal lobules VI
and VII and in automatic shifts of visual attention. Deficits were demonstrated
on both volitional saccade tasks, indicating dysfunction in the circuitry
of prefrontal cortex and its connections with the parietal cortex, and associated
cognitive impairments in spatial working memory and in the ability to voluntarily
suppress context-inappropriate responses. CONCLUSIONS: These findings demonstrate
intrinsic neocortical, not cerebellar, dysfunction in autism, and parallel
deficits in higher order cognitive mechanisms and not in elementary attentional
and sensorimotor systems in autism.