Grace E. Giles

Acute caffeine consumption enhances the executive control of visual attention in habitual consumers

Recent work suggests that a dose of 200-400 mg caffeine can enhance both vigilance and the executive control of visual attention in individuals with low caffeine consumption profiles. The present study seeks to determine whether individuals with relatively high caffeine consumption profiles would show similar advantages. To this end, we examined the effects of four caffeine doses (0 mg, 100 mg, 200 mg, 400 mg) on low- and high-level visual attention in individuals with high consumption profiles (n=36), in a double-blind study using a repeated measures design. Results from the Attention Network Test indicated that caffeine enhanced both vigilance and the executive control of visual attention, but only at the highest administered dose (400 mg). We demonstrate that in habitual consumers high doses of caffeine can produce beneficial changes in visual attention. These results carry implications for the theorized interactions between caffeine, adenosine and dopamine in brain regions mediating visual attention.

Omega‐3 fatty acids influence mood in healthy and depressed individuals

Depression is one of the most prevalent disorders in the United States, and rates of depression are higher for women than men. Despite their widespread use, drugs used in the treatment of depression are only moderately more effective than placebo in treating the disorder. Effective treatment of perinatal depression is of particular concern as treatment can influence both the mother and the developing child. Omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation may reduce symptoms of major depressive disorder and perinatal depression. The aim of the present review was to evaluate epidemiological studies examining PUFA intake and depressive symptoms in the general population, as well as double-blind, placebo-controlled trials assessing the influence of n-3 PUFA in healthy individuals and those with depression; specific consideration was given to perinatal depression and potential gender differences in the relationship. Although there is some evidence to suggest that n-3 PUFA intake is associated with reduced depressive symptoms, particularly in females, these results are generally limited to epidemiological studies, whereas results from randomized controlled trials are mixed.

Stress Effects on Mood, HPA Axis, and Autonomic Response: Comparison of Three Psychosocial Stress Paradigms

Extensive experimental psychology research has attempted to parse the complex relationship between psychosocial stress, mood, cognitive performance, and physiological changes. To do so, it is necessary to have effective, validated methods to experimentally induce psychosocial stress. The Trier Social Stress Test (TSST) is the most commonly used method of experimentally inducing psychosocial stress, but it is resource intensive. Less resource intense psychosocial stress tasks include the Socially Evaluative Cold Pressor Task (SECPT) and a computerized mental arithmetic task (MAT). These tasks effectively produce a physiological and psychological stress response and have the benefits of requiring fewer experimenters and affording data collection from multiple participants simultaneously. The objective of this study was to compare the magnitude and duration of these three experimental psychosocial stress induction paradigms. On each of four separate days, participants completed either a control non-stressful task or one of the three experimental stressors: the TSST, SECPT, or MAT. We measured mood, working memory performance, salivary cortisol and alpha-amylase (AA), and heart rate. The TSST and SECPT exerted the most robust effects on mood and physiological measures. TSST effects were generally evident immediately post-stress as well as 10- and 20-minutes after stress cessation, whereas SECPT effects were generally limited to the duration of the stressor. The stress duration is a key determinant when planning a study that utilizes an experimental stressor, as researchers may be interested in collecting dependent measures prior to stress cessation. In this way, the TSST would allow the investigator a longer window to administer tasks of interest.

Omega-3 fatty acids and stress-induced changes to mood and cognition in healthy individuals

Omega-3 fatty acid (n-3 PUFA) intake is associated with improved mood and cognition, but randomized controlled trials addressing the causal nature of such relationships are less clear, especially in healthy, young adults. Stress is one potential mechanism by which n-3 PUFAs may influence mood. Thus the present aim is to evaluate the influence of n-3 PUFA supplementation on stress-induced changes to mood, cognition, and physiological stress markers in healthy, young adults. Using a double-blind, placebo-controlled design, 72 young adults were randomized to receive 2800mg/day fish oil (n=36, 23 females) or olive oil control (n=36, 22 females) for 35days. Subjects completed measures of mood and cognition before supplementation, and two times after supplementation: following an acute stressor or non-stressful control task. The stress induction was effective in that the stressor impaired mood, including augmenting feelings of tension, anger, confusion and anxiety, reduced accuracy on a cognitive task measuring attentional control and the ability to regulate emotion, and increased salivary cortisol and pro-inflammatory cytokine interleukin-1β (IL-1β). Rated anger and confusion increased with stress in the olive oil group, but remained stable in the fish oil group. However, fish oil had no further effects on mood, cognitive function, cortisol, or IL-1β. Fish oil exerted few effects in stressful and non-stressful situations, consistent with findings showing little influence of n-3 PUFA supplementation on mood and cognition in young, healthy individuals. Potential target populations who would more likely benefit from increased n-3 PUFA intake are discussed.

Acute exercise increases oxygenated and deoxygenated hemoglobin in the prefrontal cortex.

Both acute and chronic exercise is consistently associated with a number of benefits to physical and mental health, including cardiovascular function, body weight, mood, and cognition. Near-infrared spectroscopy is an ideal method to measure changes in oxygenated and deoxygenated hemoglobin (O2Hb and dHb) levels in the prefrontal cortex (PFC) during exercise, to better understand the locus of such changes in affective and cognitive processes. The present study tracked time-dependent changes in O2Hb and dHb levels in the PFC as a function of parametrically manipulated target exercise intensity. Near-infrared spectroscopy was conducted as regular exercisers completed a 30-min bout of exercise with one of three target intensities: 52% (low condition), 68% (moderate condition), or 84% (high condition) of age-adjusted maximum heart rate. Heart rate data confirmed that the participants reached their goal intensities immediately, after 10 min, or after 20 min, respectively. Data showed that O2Hb and dHb levels in the PFC increased as a function of both exercise load and duration. An 84%>68%>52% difference was evident after 18 min of cycling for O2Hb and after 23 min of cycling for dHb. The present results add to the growing body of literature showing that at submaximal levels, increasing exercise intensities reliably promote prefrontal cerebral oxygenation.

Caffeine-induced physiological arousal accentuates global processing biases.

The effects of caffeine-induced arousal on global versus local object focus were investigated in non-habitual consumers using a double-blind, within-subjects, repeated-measures design. Following an overnight fast, low caffeine consumers (N=36; M=42.5mg/day caffeine) completed 5 counterbalanced test sessions (normal consumption, 0mg, 100mg, 200mg, and 400mg) separated by at least 3 days. During each session, volunteers either consumed their normal amount of caffeine or were administered 1 of 4 treatment pills. One hour later they completed two tasks assessing visual attention, in counterbalanced order. Measures of mood, salivary caffeine and cortisol were taken at multiple time points. Dose-dependent elevation of caffeine in the saliva demonstrated the experimental manipulation was effective. Furthermore, analyses of the mood and arousal measures detected consistent changes on arousal subscales and caffeine administration elevated saliva cortisol. Analyses of the visual attention tasks revealed that caffeine-induced physiological arousal produced global processing biases, after as little as 100mg caffeine. These data suggest caffeine consumption may influence how individuals attend to and process information in their environment and could influence daily tasks such as face recognition, learning new environments and navigation, especially for those who normally consume little caffeine.

The Effects of Load Carriage and Physical Fatigue on Cognitive Performance.

In the current study, ten participants walked for two hours while carrying no load or a 40 kg load. During the second hour, treadmill grade was manipulated between a constant downhill or changing between flat, uphill, and downhill grades. Throughout the prolonged walk, participants performed two cognitive tasks, an auditory go no/go task and a visual target detection task. The main findings were that the number of false alarms increased over time in the loaded condition relative to the unloaded condition on the go no/go auditory task. There were also shifts in response criterion towards responding yes and decreased sensitivity in responding in the loaded condition compared to the unloaded condition. In the visual target detection there were no reliable effects of load carriage in the overall analysis however, there were slower reaction times in the loaded compared to unloaded condition during the second hour.

Caffeine and theanine exert opposite effects on attention under emotional arousal

Tea is perceived as more relaxing than coffee, even though both contain caffeine. L-theanine in tea may account for the difference. Consumed together, caffeine and theanine exert similar cognitive effects to that of caffeine alone, but exert opposite effects on arousal, in that caffeine accentuates and theanine mitigates physiological and felt stress responses. We evaluated whether caffeine and theanine influenced cognition under emotional arousal. Using a double-blind, repeated-measures design, 36 participants received 4 treatments (200 mg caffeine + 0 mg theanine, 0 mg caffeine + 200 mg theanine, 200 mg caffeine + 200 mg theanine, 0 mg caffeine + 0 mg theanine) on separate days. Emotional arousal was induced by highly arousing negative film clips and pictures. Mood, salivary cortisol, and visual attention were evaluated. Caffeine accentuated global processing of visual attention on the hierarchical shape task (p < 0.05), theanine accentuated local processing (p < 0.05), and the combination did not differ from placebo. Caffeine reduced flanker conflict difference scores on the Attention Network Test (p < 0.05), theanine increased difference scores (p < 0.05), and the combination did not differ from placebo. Thus, under emotional arousal, caffeine and theanine exert opposite effects on certain attentional processes, but when consumed together, they counteract the effects of each other.

Caffeine increases false memory in nonhabitual consumers

Insight into caffeines equivocal effects on memory can be derived from work suggesting both emotional arousal and psychosocial stress increase false memory rates without increasing veridical memory. This study investigated how a range of caffeine doses affect veridical and false memory formation in nonhabitual consumers. A double-blind, repeated-measures design with caffeine (0 mg, 100 mg, 200 mg, 400 mg caffeine) was used to examine memory using the Deese-Roediger-McDermott (DRM) paradigm. Results showed that caffeine modulated arousal levels, peaking at 200 mg and returning to near baseline levels at 400 mg. Main effects of caffeine demonstrated higher critical lure recall and recognition ratings (i.e., false memory) as a function of dose, again peaking at 200 mg. Those who showed the highest arousal increases as a function of caffeine also tended to produce the highest false recall and recognition rates. Veridical memory was not affected. Results demonstrate that consumption of as little as 100 mg of caffeine elicits reliable inverted-U shape changes in arousal and, in turn, false memories in individuals who do not habitually consume caffeine.

Omega-3 Fatty Acids and Cognitive Behavior

Omega-3 polyunsaturated fatty acids (PUFAs) may influence cognition throughout the lifespan. This chapter will discuss how omega-3 PUFA supplementation may impact cognitive development in infants and children, cognitive performance in young adults, and age-related cognitive impairment in older adults. Research examining omega-3 PUFA supplementation in mothers and children shows positive effects on certain aspects of cognition; however, there is less evidence to support a role for omega-3 PUFAs in global indices of cognitive development. Studies in young adults are quite limited, with conflicting effects of omega-3 PUFAs on mood and cognitive measures, particularly executive function. In older adults, while epidemiological studies suggest that higher omega-3 PUFA intake and plasma and/or erythrocyte levels are associated with reduced cognitive decline, results from randomized controlled trials are less consistent. Though evidence points to a beneficial influence of omega-3 PUFAs on cognitive performance across the lifespan, the conclusions remain tenuous and this issue remains a topic in need of future research.