Autism-World

The cerebellum is probably the main structure that is being studied in cases of autistic disorder. According to Fatemi et al. (2003) the cerebellum plays an important role in movements, coordination and learning and may be involved with language, sensory and cognitive developments; it receives sensory and motor input and regulates these systems mostly by autonomic means. The cerebellar cortex also has ten lobules. Within the cortex lies Purkinje cells. Purkinje cells are “large neurons intercalated between the granular and molecular layers [of the cerebellum]???????[their] dendrites synapse on afferent fibers and several other neurons??????? [their] axons provide the only efferent pathway for impulses to leave the cerebellum” (Fatemi et al. 2003). Basically, Purkinje cells are responsible for inhibiting other brain cells.

It has been found that the autistic cerebellum is different. Fatemi et al. (2003) states that, through other studies, the vermal lobules VI and VII show incomplete development. Purkinje cells are deeply affected as well. According to Acosta & Pearl (2003) the number of Purkinje cells in the cerebellum are less then those with normal brains. Since these cells inhibit other brain cells, having a low density of them may “explain the stereotyped and overactive behaviors sometimes seen in persons with autism” (Alloy et al. 1999). In general, it has been found that people with autistic disorder have a smaller cerebellum and a low density of Purkinje cells. More studies are being done on the exact effect this have. The direct cause of this, however, is still being reviewed.

The minicolumn “contains a repetitive array of afferent inputs, intrinsic microcircuitry, and efferent outputs infusing the structure with a putative role as a physiological unit” (Acosta & Pearl, 2003). It is the smallest level of cortical vertical organization. It is the “basic unit of circuitry within the brain by tying together interacting afferent, interneuronal, and efferent connections???????[which aid in] information processing” (Cassanova et al. 2002). In the autistic brain, it has been found that these minicolumns are much smaller and far more numerous than a normal brain (Acosta & Pearl, 2003). Basically, the brain affected by autism has more processing units than that of a normal brain. It would seem that having more processing units would prove to be an advantage. However, thalamic afferent terminals (which receive information from the minicolumns) remain the same in the brain with autism which results in “???????the failure to assimilate extra processing unites [and] may result in cortical “noise” that then overtaxes the system???????and would affect the ability to discriminate between competing types of sensory information” (Acosta & Pearl, 2003).

There have been other findings in the anatomy of the brain. Neurons (which transmit nerve impulses) have been found to be smaller, more densely packed and have less branching dendrites (Acosta & Pearl, 2003). EEG studies have shown reduced activity in the frontal (personality and traits, cognition, memory) and temporal (auditory area and also site of memory retrieval) lobes (Alloy et al. 1999). Imbalance of serotonin (may play in the regulation of mood as well as other behaviors) and dopamine (a “feel good” receptor) have been found as well (Acosta & Pearl, 2003). The effects of these abnormalities continue to be studied.

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This entry was posted on Monday, October 1st, 2007 at 11:19 pm and is filed under Definition of Autism.