Hilda Koopman is a co-author on a PNAS paper arguing that yes, there (seems to be/is) a Neural correlate of syntactic operation Merge. From the abstract:
Our results provide initial intracranial evidence for the neurophysiological reality of the merge operation postulated by linguists and suggest that the brain compresses syntactically wellformed sequences of words into a hierarchy of nested phrases.
Matthew J. Nelsona, Imen El Karoui, Kristof Giber, Xiaofang Yang, Laurent Cohen, Hilda Koopman, Sydney S. Cash, Lionel Naccacheb, John T. Hale, Christophe Palliera and Stanislas Dehaene, Neurophysiological dynamics of phrase-structure building during sentence processing, PNAS 2017 ; published ahead of print April 17, 2017, doi:10.1073/pnas.