Some aspects of the organization of the thalamic reticular complex

TLDR

Anatomical tracing using anterograde and retrograde transport of labeled proteins has been employed to study connections between the thalamic reticular complex, intralaminar nuclei, and striatum. The study aimed to map the connections between the thalamic reticular complex, dorsal thalamus, and cerebral cortex using horseradish peroxidase tracing. Tracing revealed that thalamo‑cortical and cortico‑thalamo‑cortical projections form nucleus‑specific terminal zones in the reticular complex, yet the extensive dendritic overlap causes unspecific sampling, and the reticular complex projects only back to dorsal thalamic nuclei without sending fibers to ventral thalamus or cortex.

Abstract

Abstract Anatomical methods which depend upon the anterograde axonal transport of isotopically labeled neuronal proteins or the retrograde axonal transport of the enzyme. Horseradis peroxidase, have been used to elucidate the relationships between the reticular complex and the dorsal thalamus and cerebral cortex. Injections of tritiated amino acide in the dorsal thalamus or cerebrasl cortex in rate, cats and monkey, show that as the bundles of thalamo‐cortical and cortico‐thalamic fibers joining a paarticular dorsal thalamic nucleus to its associated area of the cerebral cortex traverse the reticular complex, they each give rise tp dense zone of terminals occupying a sector of reticular complex which is relatively constant for that dorsal thalamic nucleus and cortical area. However, because of the wide extent of the dendritic fields of the reticular cells and the degree of overlap between the sectors of the complex subtended by adjacent dorsal thalamic nuclei and adjacent cortical areas, it is likely that the reticular complex samples thalamo‐cortical and cortico‐thalamic activity in a somewhat unspecific manner. Fibers passing to the reticular complex from the intralaminar nuclei of the thalamus appear to be associated with the projection from the intralaminar nuclei of the thalamus appear to be associatied with the projection from the intralaminar nuclei to the striatu. Injections of tritiated amino acids in the reticular complex itself and injections of horseradish peroxidase in various other parts of the brain show that the only efferent pathway from thr reticular complex terminates in the nuclei of the dorsal thalamus. The reticdular complex does not appear to send fibers to other components of the ventral thalamus nor to the cerebral cortex.