two-part correlative constructions that present an initial clause and then emphasize or expand it with a contrasting/additive second clause (e.g., the classic “not X … but Y” pattern).
The neuron activates strongly for the word "but" when it introduces a contrasting or additional element in a sentence, particularly after a comma, and especially when followed by words like "also," "as," "into," "to," or other continuation phrases.
