Latency shifts in the N2b component track phonological deviations in spoken words.
OBJECTIVE
We investigated event-related brain potentials (ERPs) elicited by a novel speech comprehension paradigm modelled after the neuropsychological Token Test. The objective of the study was to determine whether the ERPs were sensitive to differences in the initial phonemes of the speech stimuli.


METHODS
Twenty-seven healthy subjects identified incorrect spoken sentences on the computerised Token Test (CTT). The incorrect spoken sentences contained one word that did not match the previously studied animations. The initial phonemes of these words were either different than or similar to the initial phonemes of their correct counterparts.


RESULTS
Different initial phonemes were associated with an early N2b, while words having similar initial phonemes resulted in a substantially delayed N2b.


CONCLUSIONS
The delayed latency effect was due to whether the incorrect word's initial phoneme matched or mismatched that of the expected word. In both cases, this component reflected a mismatch with an existing cognitive template maintained in phonological working memory. The results indicate that this mismatching effect reflected primarily attentional detection rather than language processing.
D'Arcy
R C
RC
Department of Psychology, Life Sciences Centre, Dalhousie University, Halifax, NS, Canada. rdarcy@is2.dal.ca
Connolly
J F
JF
Crocker
S F
SF
D000328:Adult; D001921:Brain / Q000502:physiology*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D007807:Language Tests; D008297:Male; D010700:Phonetics; D011930:Reaction Time / Q000502:physiology*; D012016:Reference Values; D013060:Speech