Biomedical subjects

A F Stokes

Publications and source records attributed to A F Stokes.

4 recordsLinked to original sources

PubMed1999

When does imagery practice enhance performance on a motor task?

Imagery practice of motor tasks has been recommended for a wide range of activities as from flight training to basketball. A key question, both from a practical and a theoretical standpoint, is when during the learning process does imagery practice confer the most benefit? However, the literature does not provide clear guidance, in part because of methodological limitations. A 3 x 2 (physical practice x pretest-posttest) split-plot design was employed to investigate the effects of imagery practice on the acquisition of a discrete target at three different stages of learning. Analysis indicated that imagery practice was most beneficial in the early stages of learning and showed an inverse relationship between experience and efficacy of imagery practice. Results are discussed in terms of current theories of imagery practice and suggestions are made regarding when such practice might be best applied during skill development.

Adolescent↗

PubMed1994

Effects of alcohol and chronic aspartame ingestion upon performance in aviation relevant cognitive tasks.

Acute dosing studies of aspartame, known commercially as "NutraSweet," have failed to demonstrate any neuropsychological changes that would imply performance decrements in flight operations. Such studies may be criticized on the grounds that the administration of a single, if large, dose of aspartame is not ecologically valid. Accordingly, a double-blind chronic dosing study of aspartame was conducted using ethanol (at 0.1% BAL) as the positive control. No detectable cognitive performance decrements were associated with the aspartame condition. However, the alcohol results exhibited a pattern of asymmetric lateral brain impairment that closely resembles that observed in studies of depressive patients. These results have operational implications as well as theoretical importance.

Aerospace Medicine↗

PubMed1991

Effects of acute aspartame and acute alcohol ingestion upon the cognitive performance of pilots.

Anecdotal evidence has associated the artificial sweetener aspartame with a number of symptoms of central nervous system (CNS) dysfunction. There are, however, little scientific data concerning the effect of aspartame upon complex mental operations such as those necessary for flying an aircraft. Thirteen pilots were tested in a double-blind study using the SPARTANS cognitive test battery of aviation-relevant information-processing tasks. These tasks relate to perceptual-motor abilities, spatial abilities, working memory, attentional performance, risk taking, processing flexibility, planning and sequencing ability. Subjects were tested over five sessions consisting of pretest and posttest controls and three randomly ordered treatment sessions. The treatment conditions involved an aspartame dose of 50 mg/kg body weight, a placebo condition, and an ethyl alcohol (0.1% BAL) condition as the positive control. No detectable performance decrements were associated with the aspartame condition, although decrements in psychomotor and spatial abilities were detected in the ethanol condition. Results were found to be consistent with prior flight-simulator studies of alcohol, but do not appear to support the concerns expressed in anecdotal testimony regarding the deleterious effects of aspartame upon cognitive performance.

Aerospace Medicine↗

PubMed1991

Testing the tests--an empirical evaluation of screening tests for the detection of cognitive impairment in aviators.

The FAA has expressed concern that flight safety could be compromised by undetected cognitive impairment in pilots due to conditions such as substance abuse, mental illness, and neuropsychological problems. Interest has been shown in the possibility of adding a brief "mini-mental exam," or a simple automated test-battery to the standard flight medical to screen for such conditions. The research reported here involved the empirical evaluation of two "mini-mental exams," two paper-and-pencil test batteries, and a prototype version of an automated screening battery. Sensitivity, specificity, and positive predictive value were calculated for each sub-task in a discriminant study of 54 pilots and 62 individuals from a heterogeneous clinical population. Results suggest that the "mini-mental exams" are poor candidates for a screening test. The automated battery showed the best discrimination performance, in part because of the incorporation of dual-task tests of divided attention performance. These tests appear to be particularly sensitive to otherwise difficult-to-detect cognitive impairments of a mild or subtle nature. The use of an automated battery of tests as a screening instrument does appear to be feasible in principle, but the practical success of a screening program is heavily dependent upon the actual prevalence of cognitive impairment in the medical applicant population.

Adult↗