Lateral to the main body of the thalamus, and separated from it by the thin external medullary lamina of fibers, is a thin shell of grey matter, called the thalamic reticular nucleus (TRN) or the reticular nucleus (of the thalamus). Unlike the other thalamic nuclei, the reticular nucleus does not project to neocortex, its only efferent is an inhibitory projection into the thalamus proper. TRN receives inputs from collaterals of both thalamo-cortical and cortico-thalamic fibers, thus TRN provides a way for neocortex to selectively suppress its thalamic inputs, perhaps acting as an “attentional gate”. BTW, the TRN bears no relation to the reticular formation of the brainstem.
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