Browsing by Author "Dreyer, Anna"

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    Acute psychosocial stress enhances visuospatial in healthy males
    (SAGE Publications, 2013) Human, Robyn; Thomas, Kevin G F; Dreyer, Anna; Amod, Alysaa R; Wolf, Pedro S A; Jacobs, W Jake
    Previous research demonstrates that stress can disrupt a number of different cognitive systems, including verbal memory, working memory, and decision-making. Few previous studies have investigated relations between stress and visuospatial information processing, however, and none have examined relations among stress, visuospatial memory performance, and planning/ organisation of visuospatial information simultaneously. In total, 38 undergraduate males completed the copy trial of the Rey-Osterrieth Complex Figure Test. Those assigned randomly to the Stress group (n = 19) were then exposed to a laboratory-based psychosocial stressor; the others were exposed to an equivalent control condition. All then completed the delayed recall trial of the Rey-Osterrieth Complex Figure Test. Physiological and self-report measures of stress indicated that the induction manipulation was effective. Our predictions that control participants, relative to stressor-exposed participants, (a) take less time to complete the Rey-Osterrieth Complex Figure Test recall trial, (b) reproduce the figure more accurately on that trial, and (c) show better planning and more gestalt-based organisational strategies in creating that reproduction were disconfirmed. At recall, those with higher circulating cortisol levels (measured post-stress-induction) completed the drawing more accurately than those with lower circulating cortisol levels. Otherwise stated, the present data indicated that exposure to an acute psychosocial stressor enhanced visuospatial memory performance in healthy males. This data pattern is consistent with a previously proposed inverted U-shaped relationship between cortisol and cognition: Under this proposal, moderate levels of the hormone (as induced by the current manipulation) support optimal performance, whereas extremely high and extremely low levels impair performance.
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    Influence of Age and Cognitive Reserve on Cognitive Function in HIV-infected South African Adults
    (2021) Wagner, Marcelle; Thomas, Kevin; Combrinck, Marc; Dreyer, Anna
    Background. HIV remains a significant global public health concern. South Africa is one of the hardest-hit countries, housing more than 7 million people living with HIV (PLWH), a figure that represents more than 12% of the global infected population. Globally, HIV-associated cognitive impairment is present in almost 45% of PLWH, with 72% of that total burden found in Sub-Saharan Africa (Wang et al., 2020). The severity and trajectory of that impairment is, however, influenced by numerous risk and protective factors. This study aimed to investigate the strength of influence that two of these factors (cognitive reserve and age) have in a sample of HIV-positive South African adults. Method. Participants were 32 HIV-infected and virally suppressed adults (27 women; Mage = 41.13±9.34). They were administered the Cognitive Reserve Index Questionnaire (CRIq) and a comprehensive neuropsychological battery that assessed performance on tests of motor function, attention and working memory, information processing speed, language, memory, and executive function. They also provided 3T magnetic resonance imaging data. Bivariate correlations, independent-sample t-tests, and hierarchical regression models tested the prediction that age and cognitive reserve (as indexed by CRIq scores, fractional anisotropy, white and gray matter volume, education level, and IQ score), both independently and in interaction, will have significant effects on cognitive test performance (i.e., that increasing age and lower levels of cognitive reserve will be independently associated with poorer performance, and that older adults with lower levels of cognitive reserve will display the worst performance). Results. Regarding the association of age with global cognitive function (average performance across all tests), analyses detected a moderate negative correlation (r = -.425, p = .015.), a significant between-group difference (participants ≥ 45 years worse than those < 45 years, p = .012), and a significant proportion of variance accounted for (R 2 = .18, p = .016). There were no significant main effects of cognitive reserve, and no significant age x cognitive reserve interaction effect, on cognitive test performance. Conclusion. The current analyses confirmed the influence of age on cognition in PLWH but did not provide support for the same influence of cognitive reserve. Although neuroscience research attaches increasing importance to the construct of cognitive reserve, the lack of a universally-applied definition (and hence a standard measure) of the construct hampers investigations such as this and makes cross-study comparisons difficult. From a policy-making perspective, the contrasting findings regarding age and cognitive reserve is crucial because it is imperative that intervention efforts focus only on those modifiable factors that significantly impact cognitive function, especially in countries such as South Africa that are characterized by high HIV disease burden and limited clinical and infrastructural resources.