In the Wikipedia article on nuclei I read:
A nucleus is one of the two most common forms of nerve cell organization, the other being layered structures.
Is there a specific and plausible reason, why the thalamic reticular nucleus is called a nucleus, even though it is - anatomically - a layer?
Has the TRN once been a somehow spherical nucleus and evolved into a two-dimensional layer? Or does the TRN play a functional role that normally nuclei play, but not layers?