Neurological plausibility

Since we linguists are attempting to be realistic, we cannot treat a linguistic structure as just some kind of abstract mathematical object. In keeping with the requirements of operational plausibility and developmental plausibility, we have to recognize that linguistic structures exist in the real world and that their loci are the brains of people. And so a theory of linguistic structure needs to be consistent with what is known about the structure and operation of the brain. This is the requirement of neurological plausibility.

Source
Lamb, Sydney M. "Linguistic structure: A plausible theory" in Language Under Discussion, published online June 2, 2016.