![]() ![]() ![]() This is in contrast to short-term memory tasks where previously presented stimuli are simply reiterated. This test requires active manipulation of stimuli in which an action is required on the presented stimuli. Specifically, they highlight studies using the Paced Auditory Serial Addition Task (PASAT). ![]() Gallagher and Blader suggest that "stressful" WM tests may be more sensitive to detecting deficits in adults with ADHD. A recent meta-analysis of neuropsychological performance in adults with ADHD found effect sizes for tests measuring WM and verbal memory to be among the highest within 10 functional domains. WM, or the ability to hold information in mind, manipulate it, and use it to guide behavior, is a key component of executive functioning. The inclusion of WM subtests in the battery of neuropsychological tests in previous studies in ADHD is quite logical given the growing body of literature suggesting WM impairments associated with the disorder. They suggest that the disparity between their results and Gansler's may reflect 1) differences in the WM and response inhibition tasks used or 2) problems related to the current DSM-IV diagnostic criteria in which adults who formerly may have been classified as ADHD-CT as children, are diagnosed with the ADHD-IA subtype as adults due to a reduction of the hyperactive/impulsive symptoms and thereby no longer meet criteria for the ADHD-CT subtype. The authors found no subtype differences on tests measuring interference control, inattention, response inhibition, WM, and verbal-ideational fluency. Murphy and colleagues examined neuropsychological functioning in a large sample of ADHD adults. Also, the ADHD-IA group emitted a higher rate of Continuous Performance Test (CPT) commission errors, a somewhat counterintuitive finding because one would tend to associate such errors with impulsivity rather than inattention. The ADHD-HI group showed perseverative responding on the Wisconsin Card Sort Test, while the ADHD-IA group demonstrated difficulty in WM on the Auditory Consonant Trigrams (ACT) Test. compared ADHD-HI to ADHD-IA adults and found that the types of executive functioning deficits exhibited differed across groups. While the findings regarding subtype differences in children are mixed, even less is known about the presence of neuropsychological differences between subtypes among ADHD adults. However, other researchers have detected subtype differences or demonstrated differential performance across subtypes when making comparisons to control groups. ![]() Several pediatric studies found no or limited differences between ADHD-CT and ADHD-IA subtypes on a series of executive functioning measures. The results for documenting neuropsychological differences according to DSM-IV nosology for ADHD subtypes have been ambiguous at best. Thus, one could conclude that individuals with the ADHD-CT may be most impaired because they experience the combined symptoms of inattention plus inhibition. Indeed, there is evidence that inattentive symptoms are most associated with neuropsychological impairment across the ADHD-CT and ADHD-IA subtypes. In contrast to this hypothesis, others note (e.g., that the ADHD-CT and ADHD-IA subtypes both share inattention as a common dimension and therefore the ADHD-CT and ADHD-IA should both be impaired on tests requiring attention, processing speed, vigilance and WM. According to this hypothesis the ADHD-IA subtype is a fundamentally distinct disorder with problems in attention arising from noninhibitory mechanisms. He conceptualizes the ADHD-HI and ADHD-CT as, centrally, exhibiting deficits in behavioral inhibition that in turn lead to impairment in executive functioning and working memory (WM). Barkley is most associated with this view. Some researchers hypothesize that the ADHD-IA subtype may constitute a different type of attention disorder compared to the ADHD-HI and ADHD-CT subtypes. DSM-IV defined the disorder based on the best available research at the time, but there is debate as to whether the exiting subtypes provide an accurate description of the disorder. The psychiatric classification system for ADHD, with its various subtypes, has evolved substantially over the years. Research in pediatric ADHD has progressed to documenting differences in neuropsychological functioning at the level of the DSM-IV subtypes: Combined (ADHD-CT, both inattentive and hyperactive-impulsive symptoms), Predominantly Inattentive (ADHD-IA), and least common, Predominantly Hyperactive-Impulsive (ADHD-HI). Attention deficit hyperactivity disorder (ADHD) may be the most common childhood DSM-IV diagnosis, with 30% to 50% of cases persisting into adulthood. ![]()
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