Which of the following thalamic nuclei does not project to neocortex;
Ans. is 'b' i.e. Reticular nucleiRef. Ganong 21st/e page 195 & 260, Snells neuroanatomy 3rd/e p78First, what is Neocortex?The neocortex is the nonlimbic portion of the cerebral hemisphere.Now let us discuss the connections of various thalamic nuclei in the questionAnterior thalamic nuclei -Anterior thalamic nuclei receive afferents from the mamillary bodies and give fibers to cingulate gyrus. Cingulate gyrus is included in the limbic cortex.So it means that anterior thalamic nuclei do not project to the neocortex.Intralaminar nuclei-Efferents from intralaminar nuclei are diffuse and reach various parts of the cortex. It includes both limbic and nonlimbic areas.Pulvinar nuclei -Efferents from pulvinar nuclei project to all parts of cortex which include both limbic and nonlimbic areas.Reticular nucleiAbout Reticular nuclei of Snell's neuroanatomy states "Every thalamic nucleus except the reticular nuclei sends axons to different parts of the cortex. The output of Reticular nuclei is mainly to other thalamic nuclei"In every other neuroanatomy book, I looked into states the same fact that Reticular nuclei do not send any efferent to the cerebral cortex.So in this question, two options seem correct.One is Ant Thalamic nuclei because, though it sends fibers to other parts of cortex it does not send any fibers to the neocortex.The other correct option is reticular nuclei, it does not have any efferent to the cerebral cortexI have gone for Reticular nucleus because following text from Gray's gives some evidence of efferents from Anterior thalamic nuclei projecting to the neocortex.Gray's states about Ant. Thalamic nuclei "In addition, there appears to be a minor connection between Ant Thalamic nuclei and the dorsolateral prefrontal and posterior areas of neocortex" Gray's 38th/Ep 1086.
Intralaminar nuclei
Reticular nuclei
Pulvinar nuclei
Anterior thalamic nuclei