Neural systems for sentence processing in stuttering

The role of neurolinguistic factors in stuttering was investigated by determining whether individuals who stutter display atypical neural functions for language processing, even with no speech production demands. Event-related brain potentials (ERPs) were obtained while 9 individuals who stutter (IWS) and 9 normally fluent speakers (NS) read sentences silently. The ERPs were elicited by: (a) closed-class words that provide structural or grammatical information, (b) open-class words that convey referential meaning, and (c) semantic anomalies (violations in semantic expectation). In standardized tests, adult IWS displayed similar grammatical and lexical abilities in both comprehension and production tasks compared to their matched, normally fluent peers. Yet the ERPs elicited in IWS for linguistic processing tasks revealed differences in functional brain organization. The ERPs elicited in IWS were characterized by reduced negative amplitudes for closed-class words (N280), open-class words (N350), and semantic anomalies (N400) in a temporal window of approximately 200-450 ms after word onsets. The overall pattern of results indicates that alterations in processing for IWS are related to neural functions that are common to word classes and perhaps involve shared, underlying processes for lexical access.