Second, errors commonly seen in serial order research in younger adults most often include out-of-sequence, transposition errors, i.e., a response that is recalled in the wrong serial position. First, prior research has consistently shown that when young, healthy participants are asked to repeat numbers backward, recency effects are enhanced. Subsequent experimental research assessing serial order, such as asking participants to repeat digits backward, has been used to operationally-define a number of specific parameters related to working memory including primacy and recency effects and the generation of specific patterns of errors (see for a complete review]. Karl Lashley was among the first researchers to address what he termed The Problem of Serial Order 1. Moreover, reduced aggregate serial order recall was associated with greater MRI evidence of left-sided frontal and posterior parietal white matter alterations. found that total serial order recall was able to differentiate patients with AD versus vascular dementia who presented with MRI evidence of subcortical white matter alterations. The BDT has previously been analyzed to generate two gross aggregate measures including total any recall – tallied as the total percent recall of digits regardless of their correct serial order and believed to provide a measure of auditory span and total serial order recall – tallied as the total percent recall of digits in the exact serial order and believed to provide a measure of working memory and the capacity for mental manipulation. have been used to assess working memory deficits in both dementia and MCI. Tests that examine serial order recall, such as the Backward Digit Span Test (BDT) as described by Lamar et al. In addition to unique patterns of behavior obtained from neuropsychological measures, patients with dysexecutive MCI have also been distinguished from other MCI subtypes using and neuroimaging parameters. suggested that steeper temporal gradients may provide a useful heuristic for understanding brain-behavior relationships that underlie impairment on executive tests in patients with MCI. The emergence of this striking negative slope, or steep temporal gradient as described by Fuster, suggests difficulty maintaining mental set. found that impairment on executive tests produced by mixed and dysexecutive MCI patients were similar and remarkable in that performance deteriorated as a function of time to completion and/or test epoch. have shown that patients with amnestic MCI differ from other MCI subtypes on a variety of linguistic as well as memory parameters obtained from a serial list learning test. Second, the investigation of MCI subtypes provides an opportunity to investigate the neurocognitive constructs underlying brain-behavior relationships associated with MCI. Recent research has also shown that when mixed/dysexecutive MCI patients are defined using neuropsychological criteria there tends to be faster progression to dementia than other groups. ![]() For example, past empirical findings suggest greater reliability for the eventual emergence of dementia for amnestic and multi-domain MCI as compared to single domain dysexecutive MCI. The importance of investigating MCI subtypes revolves around several clinical as well as theoretical issues including a greater understanding of conversion to dementia and a clearer appreciation of the brain-behavior relationships that underlie MCI syndromes. Patients diagnosed with MCI can be classified as presenting with single versus multiple domain subtypes. Diagnostic criteria for MCI include the subjective complaint of memory and/or other neurocognitive problems, along with relative preservation of instrumental activities of daily living, in conjunction with objective evidence documenting a decline in memory and/or other neurocognitive abilities. Mild cognitive impairment (MCI) is generally believed to be a prodrome that often results in the emergence of dementia syndromes such as Alzheimer’s disease (AD) and is considered to be a useful construct to identify patients who are potentially at risk for developing a dementing illness.
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