olfactory brain vs nerve centre

olfactory brain and nerve centre both are nouns.

Word	Noun	Adjective	Verb	Adverb
olfactory brain	Yes	No	No	No
nerve centre	Yes	No	No	No

As nouns, nerve centre is a hypernym of olfactory brain; that is, nerve centre is a word with a broader meaning than olfactory brain:

olfactory brain: a center in the cerebral hemispheres that governs the sense of smell in lower animals; in humans it seems to mediate complex emotional behavior
nerve centre: a cluster of nerve cells governing a specific bodily process

Other hypernyms of olfactory brain include center, centre, nerve center.

olfactory brain (noun)	nerve centre (noun)
a center in the cerebral hemispheres that governs the sense of smell in lower animals; in humans it seems to mediate complex emotional behavior	a cluster of nerve cells governing a specific bodily process
	a center that provides information and control