Chronometric analysis: Clinical applications in aging and dementia

No evidence of reaction time slowing in autism spectrum disorder

A total of 32 studies comprising 238 simple reaction time and choice reaction time conditions were examined in individuals with autism spectrum disorder (n = 964) and controls (n = 1032). A Brinley plot/multiple regression analysis was performed on mean reaction times, regressing autism spectrum disorder performance onto the control performance as a way to examine any generalized simple reaction time/choice reaction time slowing exhibited by the autism spectrum disorder group. The resulting regression equation was Y (autism spectrum disorder) = 0.99 × (control) + 87.93, which accounted for 92.3% of the variance. These results suggest that there are little if any simple reaction time/choice reaction time slowing in this sample of individual with autism spectrum disorder, in comparison with controls. While many cognitive and information processing domains are compromised in autism spectrum disorder, it appears that simple reaction time/choice reaction time remain relatively unaffected in autism spectrum disorder.

Application of Hick's law of response speed in Alzheimer and Parkinson diseases

Reaction time in normal subjects is known to increase in a log-linear fashion relative to the number of alternative choices. However, this relationship (formalized as "Hick's law") has received limited investigation in populations with neurological cognitive impairment. The present study used timed sorting of standard playing cards to test Hick's law for 20 young control subjects, and 20 each of age-matched elderly subjects with Alzheimer disease, Parkinson disease, and no cognitive abnormalities. Although Parkinson patients were slowest in the simple tasks of dealing out the cards and sorting by color, Alzheimer patients showed the greatest slowing for the more cognitively complex conditions of sorting by suit and rank of the cards. The performance of all four groups followed Hick's law in displaying a significant linear relationship between response time and log2 of the number of choices. These findings suggest that, although limitations of information-processing speed in Alzheimer and Parkinson disease affected choice response time, there may be sparing of fundamental cognitive organization in these disorders.

Age-related decline of psychomotor speed: effects of age, brain health, sex, and education

A cross-sectional study into age-related decline of psychomotor speed is reported. A newly introduced choice response task was used, involving three conditions: simple reaction time (SRT), choice reaction time (CRT), and CRT with stimulus-response incompatibility. Subjects were 247 volunteers, aged 20 to 80 yr. in seven age levels. Although all subjects thought themselves to be normal and healthy, a post hoc division could be made based on biological life events (BLE, mild biological or environmental factors that can hamper optimal brain functioning, such as repeated general anesthesia). Performance was poorer by subjects who had experienced one or more such event: slowing was comparable to the effect of age, especially in the more difficult task conditions. There were significant effects of sex and education, men being consistently faster than women, and more highly educated subjects performing better than subjects with only low or medium education. These findings replicate observations from other test methods. They are also in line with several other studies giving interactions between the effects of aging and physical fitness. This study questions the validity of much research on aging, as the data suggest that a more rigorous health screening for biological life events in subjects recruited from the normal, healthy population can reduce performance effects normally ascribed to aging.

The driving advisement system: a computer-augmented quasi-simulation of the cognitive prerequisites for resumption of driving after brain injury

No other activity so starkly pits the needs of the individual recovering from brain injury against the protection of society than does operating a motor vehicle. Cognitive abilities (e.g., response to complex processing demands, impulse control, ability to sustain performance, mental flexibility, and judgment), while evident only indirectly, are essential to performance, yet few are well sampled in currently used assessment procedures, which, instead, emphasize visuo-motor coordination and reaction time. In response to this need, a computerized quasi-simulation, the Driving Advisement System (DAS), was developed and is introduced here. The DAS incorporates a set of computer-based tasks for use by professionals charged with rendering advice concerning cognitive abilities necessary for driving safely. Normative data on DAS measures were obtained from a group of over 60 safe drivers free of significant neurological impairment. Preliminary validation findings are summarized. A sample DAS-generated report for a brain-injury survivor, who sought to resume driving, is used to illustrate the graphic norm-referenced presentation of an individual's performance together with self-appraisal ratings.

Divided attention and metabolic brain dysfunction in mild dementia of the Alzheimer's type

The relationship between reaction time (RT) measures under single-task and dual-task conditions and resting levels of brain metabolism, as measured by positron emission tomography (PET), was examined in patients with mild dementia of the Alzheimer type (DAT) and age- and educationally-matched controls. Slowing of RT in dual-task but not single-task conditions correlated with reductions in brain metabolism in right premotor and right parietal association areas only for the mild DAT patients. The results suggest a relation between divided attention deficits and metabolic dysfunction of right frontal and parietal lobes in mild DAT patients.