Thalamocortical connection development

Possible evidence for a persistent fetal circuit is provided by the abnormal presence of an increased number of neurons in cerebrocortical layer I and in the subcortical white matter that has been noted in several autistic brains. These neurons have been shown to normally play an essential, transient role in the development of definitive cerebral cortical circuits, particularly in relationship to thalamocortical connections (Shatz et al., 1998 Super et al., 1998 Okhotin and Kalinichenko, 2003). In this regard, it is of interest to note that Kleinhans et al. (2008), in an fMRI functional study of face recognition, noted in ASD a failure of the significant activation of the thalamus that was noted in the controls. 

The development of serotonergic innervation to the cerebral cortex has been characterized in neonatal rats by immunohistochemical techniques and autoradiographic imaging. These experiments demonstrate early serotonergic innervation that could be involved in a transient physiological role in sensory areas of the cortex or exert a trophic influence on the development of cortical circuitry and thalamocortical connections [76]. 

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