Academic journal article Journal of Medical Speech - Language Pathology

Speech and Manual Reaction Time as a Function of Dopaminergic Medication in Parkinson's Disease

Academic journal article Journal of Medical Speech - Language Pathology

Speech and Manual Reaction Time as a Function of Dopaminergic Medication in Parkinson's Disease

Article excerpt

For the past thirty years, simple reaction time paradigms have been used to improve our understanding of limb motor control in Parkinson's disease (PD)--specifically, the ability to use advance information to complete the programming phases of movement prior to execution. The extension of this paradigm to speech reaction time provides a window into hypothesized speech motor programming deficits. To begin to understand the presence and nature of these deficits, 44 participants with idiopathic PD completed speech and manual simple reaction time tasks while optimally medicated and after a 15-hour withdrawal period. Neuropsychological, speech/language, and motor variables also were measured. Participants with PD were divided among those with hypophonia only (n = 19), mild dysarthria (n = 9), and no speech decline (n = 16). Results from the participants with PD and thirty control participants suggest that numerous, complex processes underlie even "simple" reaction time performance. Speech motor programming and initiation are implicated as possible areas of disruption in individuals with PD, particularly as speech impairment increases. Moreover, dopaminergic medication seemed to have differential effects on cognitive performance for those with atypical reaction time patterns. Effects of cognitive variables on motor programming and initiation are intriguing and necessitate further study.

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Simple reaction time (RT) tasks provide complete knowledge of the expected response. As a result, individuals are able to program the response in advance and maintain it for a brief period until registration of the go-signal (Sheridan, Flowers & Hurrel, 1987). A unifying theme among researchers is that simple RT paradigms reflect the extent to which an individual is able to use advance information to complete programming phases of a movement prior to motor execution (Berardelli et al., 2001; Byblow et al., 2002; Klapp, 2003; Muller et al., 2001; Rafal, Friedman & Lannon, 1989; Sheridan et al., 1987; Smiley-Oyen & Lowry, 2007). Thus, the simple RT paradigm can be used as a window into the programming and initiation (1) phases of movement and has often been employed to this end in individuals with Parkinson's disease (PD).

It is currently well-accepted that a limb motor programming impairment exists in PD (Gentilucci & Negrotti, 1999; Labyt, Devos, Bourriez, Cassim et al., 2003), and preliminary evidence using choice RT paradigms suggests that speech motor programming may also be affected (Spencer & Rogers, 2005). The purpose of the current study is to examine medication effects on speech programming and initiation in individuals with PD through the use of simple RT. Individuals with PD who have unaffected speech as well as those with dysarthria and/or hypophonia will be included. Moreover, as a comparison task, limb reaction time will also be measured.

To transform intention to articulation, the linguistic-symbolic representations of a thought must undergo motor planning and programming to be translated into a code that is recognized by a respiratory-phonatory-articulatory-resonatory system. The intricacies of motor programming remain enigmatic, but this term is generally used to refer to the specification of muscle commands that occurs before a motor sequence begins (van der Merwe, 1997). Speech RT research of populations--including PD (Gurd, Bessell, Watson & Coleman, 1998; Spencer & Rogers, 2005), ataxic dysarthria (Spencer & Rogers, 2005), apraxia of speech (Maas, Robin, Wright & Ballard, 2008), and healthy adults (Klapp, 1995, 1996, 2003, 2005; Netsell & Daniel, 1974; Wright et al., 2009)--has addressed issues parallel to the limb literature, such as attempting to delineate the stages of motor programming versus motor execution. However, this small body of speech RT literature is in its infancy and exists without the robust replications of the limb motor control literature. …

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