Cerebellar Tract of Cognitive Function in Autism and Neurodevelopmental Disorder
S.M. Kowsar, Shakera Akter, Ibrahim Khalilullah, Mohammad Faruque Reza, Golam Hossain, Sheikh Muhammad Abu Bakar.
The cerebellum is a classical subcortical center for motor control and is an important part of the circuitry that links sensory to motor areas of the brain. It represents 10% of total brain volume but contains more than 50% of its neurons. There is different cerebellar circuitry, among them the cortico cerebellar cortical circuit is very important, any disruption of this circuitry associated with ataxic hemiparesis, dysarthria and clumsy hand syndrome and dysfunctional prefrontal thalamic cerebellar circuitry leads to schizophrenia, cognitive dysmetria. The dentato-rubro-olivary circuit is a bidirectional pathway, forms a feedback loop between the cerebellum and brainstem, and it serves to control spinal cord motor activity, lesion in this triangle is associated with hypertrophic olivary degeneration. There is another circuitry between cerebellam and basal ganglia, which are densely interconnected and control, modify motor activity. Their connections play an important role in pathophysiology of various movement disorders or neurodevelopmental disorders. Parkinsonian tremor results from increased interaction between the basal ganglia and the cerebello- thalamo-cortical circuit. The cerebello-hypothalamo-cerebellar circuit is a bidirectional circuit both directly and indirectly between the cerebellum and hypothalamus, consist of both hypothalamo-cerebellar and cerebello-hypothalamic pathways. The functions of this circuit are so far unknown, but the neurophysiological and neuroimaging studies have demonstrated that this circuit may be involved in feeding, cardiovascular, osmotic, respiratory, micturition, immune, emotion and other nonsomatic regulation. The circuitry between cerebellum with limbic-related brain areas and paralimbic cortices suggests widespread cerebellar influence on behaviors including the experience and expression of emotion, sadness and grief, integrative hypothalamic visceral/sensory functions, pain perception, modulation, and intensity due to noxious stimuli, as well as other nonmotor behaviors. Lesions of this circuitry lead to the cerebellar cognitive affective syndrome both in adults and in children and dysfunction of this circuitry may lead to autism and neurodevelopmental disorder. Cerebellar dysfunction may play a crucial role in the etiology of autism spectrum disorder, schizophrenia, and other cognitive disorders. Although the main function of cerebellum is motor control, but it has some roles in olfactory function. In this paper we have reviewed different descriptive cerebellar circuitry and clinical consequences following their lesions.
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