The contingent negative variation as an indicator of speech discrimination difficulty.

Recent studies have illustrated the usefulness of the contingent negative variation (CNV) in exploring language processing capabilities. The purpose of this study was to investigate how CNV magnitude is influenced by speech discrimination tasks of graded difficulty. Nine young adult subjects performed easy and difficult speech discrimination tasks while cortical activity was recorded from the vertex. Stimuli consisted of consonant-vowel pairs that were presented in a background of noise. Consistently larger CNV responses were obtained for the difficult versus the easy discrimination task in the nonimperative condition. No consistent trend was found for the imperative condition. There electrophysiological results correspond well with both correct and incorrect discrimination behavior. The clinical implications of these findings are discussed.