Influence of stimulus modality and interstimulus interval in computerized measures of verbal working memory performance in Parkinson's disease

Reports of working memory in healthy and neurologically impaired individuals are commonly used in discussions of the theoretical models of working memory created to hypothesize the link between working memory and verbal comprehension. Because of the evidence implicating the frontal cortex and circuitry in working memory, the influence of verbal working memory abilities on language is of particular interest in people with Parkinson's disease (PD), a population with neurological impairment in subcortical and frontal cortex circuitry, and executive deficits that affect language processing.;Twenty four non-demented individuals with PD performed similarly to an age- and gender-matched healthy control group for all measures. Both groups performed more slowly and less accurately in a 2-back compared to a 1-back test of working memory. Response time lengthened but accuracy improved as ISI lengthened across three levels (800, 1600, and 3200 ms) in the n-back tests, indicating participants utilized the additional time to determine the correct response. Visual or auditory presentation of stimuli did not generally influence response time or accuracy, supporting an amodal theory of verbal working memory. Influential parameters of stimuli in computerized measures of working memory need to be carefully considered and reported in the continuing investigations of the complex relationship between language use and working memory.;The development of computerized measures for working memory has improved the precision of clinical researchers' assessments and provided tools for interventions. The effects of manipulating parameters of computerized tests are unclearly understood and should be carefully considered when selecting or developing computerized measures of attention or memory. Empirical studies rarely provide a strong rationale for selecting a particular interstimulus interval (ISI), which vary greatly across studies. ISI is particularly important to consider in tasks of verbal working memory, in which subjects are required to retain and manipulate information for the duration of the ISI. The influence of stimulus modality also has not been adequately explored, although Schumacher et al. (1996) conclude that verbal working memory is amodal, simply using phonological representations translated from visual or auditory stimuli.