Unusual brain growth patterns in early life in patients with autistic disorder: an MRI study.

OBJECTIVE: To quantify developmental abnormalities in cerebral and cerebellar volume in autism. METHODS: The authors studied 60 autistic and 52 normal boys (age, 2 to 16 years) using MRI. Thirty autistic boys were diagnosed and scanned when 5 years or older. The other 30 were scanned when 2 through 4 years of age and then diagnosed with autism at least 2.5 years later, at an age when the diagnosis of autism is more reliable. RESULTS: Neonatal head circumferences from clinical records were available for 14 of 15 autistic 2- to 5-year-olds and, on average, were normal (35.1 +/- 1.3 cm versus clinical norms: 34.6 +/- 1.6 cm), indicative of normal overall brain volume at birth; one measure was above the 95th percentile. By ages 2 to 4 years, 90% of autistic boys had a brain volume larger than normal average, and 37% met criteria for developmental macrencephaly. Autistic 2- to 3-year-olds had more cerebral (18%) and cerebellar (39%) white matter, and more cerebral cortical gray matter (12%) than normal, whereas older autistic children and adolescents did not have such enlarged gray and white matter volumes. In the cerebellum, autistic boys had less gray matter, smaller ratio of gray to white matter, and smaller vermis lobules VI-VII than normal controls. CONCLUSIONS: Abnormal regulation of brain growth in autism results in early overgrowth followed by abnormally slowed growth. Hyperplasia was present in cerebral gray matter and cerebral and cerebellar white matter in early life in patients with autism.

Attention coordination and anticipatory control.

The coordination of the direction of selective attention is an adaptive function that may be one of the many anticipatory tools under cerebellar control. This chapter presents neurobehavioral, neurophysiological, and neuroimaging data to support our hypothesis that the cerebellum plays a role in attentional functions. We discuss the idea that the cerebellum is a master computational system that anticipates and adjusts responsiveness in a variety of brain systems (e.g., sensory, attention, memory, language, affect) to efficiently achieve goals determined by cerebral and other subcortical systems.

The influence of pattern type on children's block design performance.

This study sought to determine what factors contribute to normal developmental changes in performance on the block design task. The target models were systematically varied to emphasize global, intermediate, and local pattern structures. One hundred children between 4.5 and 9 years of age were tested in the first experiment. Correct performance and error types differed significantly as a function of age and pattern type. Broken configuration errors were particularly common for the global patterns. In the second experiment, 48 children between 4.5 and 8 years of age were tested using designs with a superimposed grid (cued condition). Error rates were lower in the cued condition and broken configuration errors were less frequent. These results suggest that children have more difficulty parsing more cohesive patterns, but they can modify their strategies when the square matrix is provided by the pattern structure.

Impairment in shifting attention in autistic and cerebellar patients.

MRI and autopsy evidence of early maldevelopment of cerebellar vermis and hemispheres in autism raise the question of how cerebellar maldevelopment contributes to the cognitive and social deficits characteristic of autism. Compared with normal controls, autistic patients and patients with acquired cerebellar lesions were similarly impaired in a task requiring rapid and accurate shifts of attention between auditory and visual stimuli. Neurophysiologic and behavioral evidence rules out motor dysfunction as the cause of this deficit. These findings are consistent with the proposal that in autism cerebellar maldevelopment may contribute to an inability to execute rapid attention shifts, which in turn undermines social and cognitive development, and also with the proposal that the human cerebellum is involved in the coordination of rapid attention shifts in a fashion analogous to its role in the coordination of movement.

ERP Evidence for a Shifting Attention Deficit in Patients with Damage to the Cerebellum.

Abstract In a previous study, we found that patients with damage to the neocerebellum were significantly impaired in the ability to rapidly shift their attention between ongoing sequences of auditory and visual stimuli (Akshoomoff & Courchesne, 1992). In the present study, young patients with damage to the neoccrebelluni were found to be impaired in rapidly shifting their mention between visual stimuli that occurred within a single location. Event-related potentials recorded during the shifting attention experiment suggested that this reflects a deficit in the. covert ability to selectively activate and deactivate attention. These results lend Further support to the hypothesis that the neocerebellum plays a role in the ability to rapidly shift attention.

A new role for the cerebellum in cognitive operations.

Over the last 2 centuries, the predominant view of the cerebellum has been that it is part of a motor control system. Evidence is now presented that the neocerebellum, the evolutionarily newest region of the cerebellum, may also be involved in a key mental operation: the voluntary shift of selective attention between sensory modalities. It is theorized that this newly recognized function may operate via previously described sensory modulation properties of the cerebellum and its many connections with areas known to be important for selective attention, such as the pulvinar, the superior colliculus, and the parietal and frontal cortices.

Contribution of the cerebellum to neuropsychological functioning: evidence from a case of cerebellar degenerative disorder.

A detailed neuropsychological evaluation was performed on a patient with an idiopathic cerebellar degenerative disorder. Significant deficits were found in verbal and nonverbal intelligence, verbal associative learning, and visuospatial skills. These deficits were not readily explained by motor control difficulties. In contrast to the patient's moderately impaired language abilities, he was severely impaired on a test of verbal fluency and demonstrated mild naming deficits. Severe cerebellar parenchymal volume loss was demonstrated by magnetic resonance examination. Supratentorial structures showed only minimal posterior parietal and occipital sulcal prominence. On neurological examination, this patient had signs of severe involvement of the cerebellar systems and mild-to-moderate dysfunction of the corticospinal tract. As is characteristic of patients with cerebellar degeneration, there was neurophysiological evidence of subclinical involvement of auditory and somatosensory pathways at the level of the brain stem. Since relatively little cerebral cortical atrophy was noted in this patient, these findings suggest that an intact cerebellum is important for normal cognitive functions.

Block constructions of chronic alcoholic and unilateral brain-damaged patients: a test of the right hemisphere vulnerability hypothesis of alcoholism.

A detailed analysis of the block construction performance of chronic alcoholics, unilateral brain-damaged patients, and normal control subjects was conducted to test two hypotheses: (a) that alcoholics perform similarly to right-hemisphere damaged (RHD) patients but not left-hemisphere damaged (LHD) patients; and (b) that unilateral brain-damaged patients display qualitatively different strategies and errors. Differences in performance without a time limit and broken configuration errors suggest that the alcoholics have not incurred the type of visuospatial impairment characteristic of RHD patients. The LHD and RHD patients showed qualitative differences in their strategies and errors. Implications of the findings for research and clinical assessment of visuospatial dysfunction are discussed.