Producing speech involves processing linguistic information at a cognitive level (henceforth, psycholinguistic planning) while, simultaneously, maintaining control at a speech motor level. Speech-language pathologists pay close attention to the latter in the diagnosis and treatment of adulthood stuttering, while little if any attention is paid to the performance of the cognitive machinery driving speech production. Psycholinguistic planning largely involves the cognitive processing of lexical knowledge on the path to speaking;processing that can, to some extent, be elicited via picture naming. Three psycholinguistic mechanisms that drive picture naming are: 1) Activation spreading. Words are activated and compete for selection in the mental lexicon on the path to picture naming. 2) Lexical retrieval. When a word is selected its semantic and phonological features are retrieved and used to generate a linguistic blueprint, or surface structure. 3) Internal error monitoring. The linguistic blueprint is monitored for accuracy before being transformed into speech motor movements. Fluent and accurate speaking depends as much on the efficiency with which these mechanisms operate as it does on speech motor control. Thus, a crucially important aim is to characterize psycholinguistic mechanisms in adults who stutter (AWS). Behavioral psycholinguistic research conducted to date has been limited in its ability to meet this aim. Here, an innovative cognitive neuroscientific approach, involving event-related potentials (ERPs), will be utilized. ERPs are reflexive changes in brain electrophysiological activity, recorded non- invasively at the scalp that can index specific psychological mechanisms with precision on the order of milliseconds. ERPs can be recorded as people prepare to name pictures and make lexical decisions about picture names they generate. ERPs elicited on the path to picture naming may comprise several components, some that respond via changes in amplitude and latency as activation spreading, lexical retrieval and internal error monitoring, respectively, unfold in real time. In three experiments, those ERP components will be compared in AWS versus adults who do not stutter (AWNS) to answer the following questions: 1) Does activation spreading operate typically in AWS, as evidenced in the amplitude of the N400 ERP component elicited during a picture-word priming task? 2) Does word retrieval operate along a typical time-course in AWS, as evidenced in the time-course of two ERP components - Lateralized Readiness Potential and NoGo N200 - elicited during a dual-choice lexical decision task? 3) Does internal error monitoring operate typically in AWS, as evidenced in the amplitude of Error Related Negativity elicited during a forced-error lexical decision task? Results will reveal whether brain electrophysiological activity in AWS may differ from that of AWNS in psycholinguistic mechanisms that mediate the activation, retrieval, and monitoring of lexical knowledge on the path to picture naming. Findings will have implications for the development of psycholinguistically-focused clinical diagnostic and intervention tools for stuttering.
Although efficient psycholinguistic planning is requisite for fluent and accurate speech production, psycholinguistic performance is not a standard consideration in the clinical diagnosis and treatment of adulthood stuttering. Understanding precisely how AWS activate, retrieve, and monitor lexical knowledge on the path to speaking could improve the efficacy of intervention for stuttering, an important goal in fostering the psychosocial and vocational prospects of adults who stutter. Results of this research will have implications for the development of psycholinguistically-focused assessment and treatment tools for stuttering.
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