Biomedical subjects

Brian Stollery

Publications and source records attributed to Brian Stollery.

4 recordsLinked to original sources

PubMed2005

Cognitive performance inconsistency: intraindividual change and variability.

Although many studies have examined inconsistency of cognitive performance, few have examined how inconsistency changes over time. 91 older adults (age 52 to 79) were tested weekly for 36 consecutive weeks on a series of multitrial memory speed (i.e., letter recognition) tasks. A number of multivariate techniques were used to examine how individuals' level of inconsistency changed across weeks and how this change was related to interindividual differences in age and intelligence. Results indicated that (a) inconsistency of performance is a construct separate from the underlying performance ability (i.e., memory speed); (b) inconsistency reduces exponentially with practice; (c) individuals with higher scores on tests of fluid general intelligence (G-sub(f)) reached lower asymptotic levels of inconsistency compared to lower scorers; and (d) after controlling for the systematic effects of practice, variability in inconsistency from week-to-week was more pronounced for individuals with lower G-sub(f) scores compared to individuals with higher scores.

Aged↗

PubMed2005

Memory processing and the glucose facilitation effect: the effects of stimulus difficulty and memory load.

Previous research has consistently found enhancement of memory after the ingestion of a glucose containing drink. The aims of the present study were to specify more precisely the nature of this facilitation by examining the cognitive demand hypothesis. This hypothesis predicts greater glucose induced facilitation on tasks that require significant mental effort. In two experiments, both employing an unrelated sample design, participants consumed either 25 g of glucose or a control solution. In experiment 1, participants first studied low and high imagery word-pairs and memory was assessed 1-, 7- and 14-days later by cued recall. Overall, glucose enhanced both encoding and consolidation processes only for the more difficult low imagery pairs. In experiment 2, the degree of mental effort in a verbal memory task was manipulated in two ways: (1) by varying the phonological similarity of the words; and (2) by varying the length of word lists. Glucose was found to enhance memory only for longer word lists. These data are consistent with the idea that glucose is especially effective in demanding memory tasks, but place some limits on the forms of difficulty that are susceptible to enhancement.

Adolescent↗

PubMed2004

The impact of glucose ingestion and gluco-regulatory control on cognitive performance: a comparison of younger and middle aged adults.

A great deal of research has been devoted to the issue of whether the ingestion of a glucose containing drink facilitates cognitive performance. However, it remains unclear exactly how age and individual differences in gluco-regulatory control mediate a boost in cognitive functioning. The present study investigates these issues further. A repeated measures (25 g vs 50 g glucose vs placebo) counterbalanced, double-blind design was used with 25 younger and middle-aged adults. A battery of memory and non-memory tasks was administered; including tests of episodic and semantic memory, attention and visuospatial functioning. Glucose ingestion largely facilitated performance on tasks with a memory component. Notably, task demands and age (young vs middle-aged) contributed to the magnitude of memory enhancement. This finding suggests an age- and load-specific benefit of glucose intake. In addition, evidence suggests greater facilitation in individuals with good glucose regulation. These data are discussed in relation to the idea that glucose specifically affects neural mechanisms supporting memory functioning (i.e. the hippocampus), which are known to decline in ageing. Importantly, the present investigation adds to the growing body of literature showing the utility of glucose supplementation as memory enhancers.

Adolescent↗

PubMed2004

Evidence for disproportionate dual-task costs in older adults for episodic but not semantic memory.

Previous research demonstrates that older adults are poor at dual tasking, but there is less agreement on whether their decrement is worse than that predicted from single-task performance. This study investigated whether task domain moderates dual-task costs in old age. In two experiments, young and older adults retrieved either previously learned associates (episodic retrieval) or overlearned category members (semantic retrieval) under single or working-memory load conditions, using cued recall (Experiment 1) and recognition (Experiment 2) procedures. In both experiments the proportional costs of dual tasking were age invariant for semantic retrieval but were particularly marked for episodic retrieval, although the size of the age effect was reduced in recognition compared to cued recall. The data suggest that age effects in dual tasking may be domain specific.

Adult↗