Trail-making Task Research Articles

Cognitive switching processes in young people with attention-deficit/hyperactivity disorder

Patients with attention-deficit/hyperactivity disorder (ADHD) can be slow at switching between stimuli, or between sets of stimuli to control behaviour appropriate to changing situations. We examined clinical and experimental parameters that may influence the speed of such processes measured in the trail-making (TMT) and switch-tasks in cases with ADHD combined type, their non-affected siblings and unrelated healthy controls. The latency for completion of the trail-making task controlling for psychomotor processing (TMT-B–A) was longer for ADHD cases, and correlated with Conners’ ratings of symptom severity across all subjects. The effect decreased with age. Switch-task responses to questions of “Which number?” and “How many?” between sets of 1/111 or 3/333 elicited differential increases in latency with condition that affected all groups. But there was evidence for increased symptom-related intra-individual variability among the ADHD cases, and across all subjects. Young siblings showed familiality for some measures of TMT and switch-task performance but these were modest. The potential influences of moderator variables on the efficiency of processing stimulus change rather than the speed of processing are discussed.

Neuropsychological sequelae of digital mobile phone exposure in humans

The effect of electromagnetic fields from digital mobile phones (DMP) on cognitive functioning is an area receiving increased attention. This study compares the performance of 120 volunteers on 8 neuropsychological tests during real or sham exposure to a DMP set to maximum permissible radiofrequency power output. When results were adjusted for known covariates (gender, age, or education), several alterations at significance levels of p < 0.05 were obtained. Of these, simple and choice reaction times (CRT) showed strong evidence of impairment. Further, performance on the Trail Making Task (TMT) improved, supporting the hypothesis that DMP radiofrequency emissions improve the speed of processing of information held in working memory.

Neuropsychological sequelae of 50 Hz magnetic fields

Purpose : The effects of occupational levels of 50 Hz magnetic fields on cognitive function were studied on 30 human volunteers. Materials and methods : The exposure system consisted of Merrit-type modified Helmholtz coils forming a 2 m cube, employing two orthogonal sets of coils producing a 28 μ T (resultant) circularly polarized 50 Hz magnetic field. Subjects sat at a desk within the coils where they undertook a series of verbal and written tests of cognitive function. After these tests were concluded (~30min) subjects were either exposed or sham-exposed to fields (double-blinded) for 50min. A second set of tests (employing alternate versions) was administered 20min from the start of this period. Each subject returned after 7 days to repeat the sequence, but with the opposite field/sham status. Results and conclusions : The majority of the results indicated no significant effect of exposure on cognition. However, verbal recall of a list of 15 words after an interference (the different list) was significantly impaired in the 'field on' condition. This is indicative of a reduction in short-term memory of words. The mean baseline score was somewhat higher in the 'field on' condition. However, this difference is within the parameters of normal variation. The other significant result occurred during performance of a trail-making task (alternating 1-A-2-B-3-C, etc.), with a decrease in performance as a result of exposure to the 50 Hz field. This task requires executive functioning with a working memory load, involving parietal spatial processing coordinated by prefrontal executive processing. In summary, the data are suggestive of detrimental effects on cognitive processes, particularly short-term learning and executive functioning. However, larger sample sizes are required to demonstrate statistically a more specific pattern of cognitive effects.

The Edinburgh cohort of HIV-positive injecting drug users at 10 years after infection: a case-control study of the evolution of dementia.

To examine the evolution of dementia in HIV-positive injecting drug users (IDU) in Edinburgh. Case-control study. Twenty six (6%) out of 404 patients in the Edinburgh cohort of HIV-positive IDU who have developed HIV-1-associated dementia in the 10 years since infection and seroconversion. Patients were tested repeatedly, where possible, on a range of neuropsychological and neurophysiological measures. The results from patients with dementia were compared with those of age, sex and IQ-matched non-demented HIV-positive controls from the cohort. An auditory event-related potential (P3 or P300), a neurophysiological measure of cognitive function, detected the onset of a marked slowing of cognitive and psychomotor functions. Neuropsychological measures that involve the speed of information processing such as the Trail-Making task also identified the early stages of dementia. Dementia was associated with a more advanced stage of systemic disease, increased rates of decline in CD4 cell counts and markedly reduced survival compared with the non-demented controls. No evidence for a protective effect of treatment with zidovudine was detected. In the first 10 years after infection with HIV-1 dementia is an individual development, not the clinical extreme of general intellectual impairment, and had occurred in at least 6% of our IDU cohort. Future questions concern the long-term rate of dementia, the critical neuropathological change and the true potential for early treatment.

A Single Photon Emission Computerised Tomography Study of Regional Brain Function in Elderly Patients with Major Depression and with Alzheimer-Type Dementia

The uptake, at rest, of 99mTc-exametazime into different brain regions was compared using SPECT for 20 elderly subjects with major depressive disorder, 20 with Alzheimer-type dementia, and 30 age-matched normal volunteers. Uptake was referred to calcarine-occipital cortex as a reference sensory area. Cross-sectional differences between the three groups were highly statistically significant, but reflected primarily the reductions in cortical uptake in the Alzheimer group. A detailed comparison of depressed patients and controls identified decrements in anterior cingulate, temporal and frontal cortex and in caudate and thalamus in men only. These decrements were correlated with impairment of performance on a trail-making task, but were also associated with continuing treatment with antidepressants or benzodiazepines. However, most depressed patients had quantitatively normal scans for posterior parietal association cortex, and this suggests that SPECT may find a limited role in the differential diagnosis of depression and dementia. The reduced brain function in some depressed patients may parallel the findings from studies of brain structure in elderly depressives; there was between good outcome at 6-18 months and increased tracer uptake in subcortical areas.

The effects of sleep deprivation on divergent thinking and attention processes.

Twelve male undergraduate students were deprived of sleep for one night and were tested with a series of cognitive tasks. Their performance was compared to the performance of thirteen control subjects. Two hourly tasks and three occasional tasks were administered in order to examine cognitive performance following sleep loss. In an attempt to replicate the findings of Horne (1988a), the figural form of the Torrance Tests of Creative Thinking was administered. To explore the effects of short-term sleep deprivation on attention, the following tasks were also administered: a working memory task, a trail-making task, a vowel/consonant discrimination task, and a letter recognition task. Results of the Torrance test, trail-making task and letter recognition task revealed decreases in cognitive abilities following sleep loss, although all tasks required less than 10 minutes to administer. The results of this study suggest that cognitive measures following sleep deprivation have not been adequately explored. Results support the hypothesis that sleep serves a function of cognitive restitution, particularly in the maintenance of attentional mechanisms.

Mental Efficiency and Hypoglycemia

Cognitive functioning after a mild hypoglycemic episode (MHE) was studied in 24 school-age children with insulin-dependent diabetes mellitus (IDDM). All children were administered a battery of neuropsychological tests which included digit spans, trailmaking tasks, Klove Mathews Maze test, and finger-tapping and handwriting tasks. The experimental group (n = 14) consisted of children who were tested initially after resolution of hypoglycemic symptoms following a documented MHE (Chemstrip bG less than or equal to 60 mg/dl with symptoms). The comparative group (n = 10) consisted of children who were initially evaluated after documentation of euglycemia. Comparison of the comparative group scores with test scores of the experimental group after recovery from the MHE demonstrated statistically significant differences (p less than 0.05 by dependent t-tests) in five of 12 tasks. No differences were noted when second trial scores of both groups were compared when they were retested after documentation of euglycemia. This study suggests that a discrepancy exists between the recovery rate of physical symptoms and cognitive function in children following a MHE.