Sentence comprehension in proficient adult cochlear implant users: On the vulnerability of syntax

Abstract

Comprehending language via a cochlear implant, a neural prosthesis which stimulates the acoustic nerve electrically, poses a remarkable challenge to the brain. We investigated auditory sentence comprehension in a group of thirteen high proficient adult cochlear implant patients using event-related brain potentials. Four types of sentences were examined: correct sentences with either high (1) or low (2) expectancy of the sentence final word (cloze probability), semantically incorrect sentences (3), and sentences violating the argument structure of the verb (4). Participants judged the acceptability of the sentences. Relative to correct sentences with a high cloze probability all other conditions elicited a N400 effect in both the patient group and a matched control group, although the timing of the effect differed between the two groups. Moreover, whereas the argument structure violation elicited a late positivity in addition to the N400 effect in the control group, no such effect was observable in the cochlear implant group. We take these data to indicate that under adverse input conditions, processes of syntactic repair reflected in the P600 effect, are much more vulnerable than processes of semantic integration reflected in N400 effects.