The thalamic reticular nucleus is part of the ventral thalamus that forms a capsule around the
thalamus
The thalamus (: thalami; from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter on the lateral wall of the third ventricle forming the wikt:dorsal, dorsal part of the diencephalon (a division of ...
laterally. However, recent evidence from mice and fish question this statement and define it as a dorsal thalamic structure. It is separated from the thalamus by the
external medullary lamina. Reticular nucleus cells are all
GABAergic
In molecular biology and physiology, something is GABAergic or GABAnergic if it pertains to or affects the neurotransmitter gamma-aminobutyric acid (GABA). For example, a synapse is GABAergic if it uses GABA as its neurotransmitter, and a GABAergic ...
, and have
discoid dendritic arbors in the plane of the nucleus.
Thalamic Reticular Nucleus is variously abbreviated TRN, RTN, NRT, and RT. The TRN is found in all mammals.
Input and output
The thalamic reticular nucleus receives input from the
cerebral cortex
The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. It is the largest site of Neuron, neural integration in the central nervous system, and plays ...
and dorsal thalamic nuclei. Most input comes from collaterals of fibers passing through the thalamic reticular nucleus.
The outputs from the primary thalamic reticular nucleus project to dorsal thalamic nuclei, but never to the cerebral cortex. This is the only thalamic nucleus that does not project to the cerebral cortex. Instead it modulates the information from other nuclei in the thalamus. Its function is modulatory on signals going through the thalamus (and the reticular nucleus).
The thalamic reticular nucleus receives massive projections from the external segment of the
globus pallidus
The globus pallidus (GP), also known as paleostriatum or dorsal pallidum, is a major component of the Cerebral cortex, subcortical basal ganglia in the brain. It consists of two adjacent segments, one external (or lateral), known in rodents simpl ...
, thought to play a part in disinhibition of thalamic cells, which is essential for initiation of movement (Parent and Hazrati, 1995).
It has been suggested that the reticular nucleus receives afferent input from the
reticular formation
The reticular formation is a set of interconnected nuclei in the brainstem that spans from the lower end of the medulla oblongata to the upper end of the midbrain. The neurons of the reticular formation make up a complex set of neural networks ...
and in turn projects to the other thalamic nuclei, regulating the flow of information through these to the cortex. There is debate over the presence of distinct sectors within the nucleus that each correspond to a different sensory or cognitive modality.
For original connectivity anatomy see Jones 1975.
For discussion of mapping and cross modality pathways see Crabtree 2002.
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Thalamic nuclei