[The N2 component of event-related potentials to CV syllables in a task-free situation]

Event-related potentials (ERPs) were recorded while subjects simply listened to sequences of consonant-vowel (CV) syllables. Each sequence was presented in random order and consisted of two kinds of CV syllables--90% ('frequent') and 10% ('rare deviant'), respectively. The features separating these two syllables were varied in phoneme (consonant and/or vowel) or intensity in different runs. In all eight conditions, a fronto-centrally dominant, negative wave peaking around 200 ms (N2) was observed for the deviants. The shorter latency N2 was found for the separating features of vowels or intensities but not for consonants. The results were interpreted as showing that N2 reflects a covert orienting response to rare deviants and that its latency can serve as an index for identifying the separating feature. Observation of N2 in the task-free situation suggested that it might be a useful tool for assessing linguistic discriminability in a clinical setting.