Chronic exercise and neuropsychological function in healthy young adults: a randomised controlled trial investigating a running intervention.

Despite the well-known physical and mental health benefits of regular exercise, many of the world's population, including healthy young adults, grossly undershoot recommended physical activity levels. Chronic exercise has potential to improve cognitive performance and affect in most age groups. However, there is currently a poverty of relevant research in young adults, especially randomised controlled trials. To address this, the current research investigated the effects of a running intervention on neuropsychological function (cognition and affect) in young adults. We predicted that following a running intervention, neuropsychological performance would improve alongside increases in aerobic fitness. Thirty-two healthy young adult university students were randomised (using a 3:1 ratio) into an intervention or control group, with the intervention group (n = 24) asked to run for 30 min three times a week over a 6-week period and the control group (n = 8) asked to maintain their current level of exercise over a 6-week period. We assessed fitness, cognitive performance, affect and running enjoyment at baseline and follow-up, and runners recorded the environmental conditions of their runs. Repeated measures ANCOVAs failed to find any significant effects of the running intervention on fitness or the neuropsychological measures. Anecdotal evidence supported running environment and enjoyment as potentially relevant factors. The failure to find any fitness improvements, which likely underpins the lack of neuropsychological improvements, highlights the importance of monitoring exercise sessions. Coupled with other insights gained from this trial, this article may prove useful towards future endeavours to develop exercise interventions beneficial to young adults.TRN: ACTRN12621000242820, Date of registration: 08/03/2021.

3-Year test-retest reliability in Parkinson's disease and healthy older adults: The Parkinson's progression markers initiative study.

Repeated neuropsychological assessments are often conducted in clinical and research settings to track cognitive changes over single or multiple intervals in patients with Parkinson's disease (PD). Yet few studies have documented test-retest reliability in PD. To address this gap, we used data from the Parkinson's Progression Markers Initiative (PPMI) to investigate the reliability of five well-known neuropsychological tests over a 3-year follow-up assessment in early-stage PD with either normal (PD-NC; N = 158) or abnormal (PD-AC; N = 39) cognitive screening, categorized based on recommended cutoffs for the Montreal Cognitive Assessment (MoCA), and healthy older adults (HOA; N = 102). All participants analyzed maintained the same cognitive status category across the assessment points. Intraclass correlation coefficients (ICCs) estimated reliability. The overall ICCs calculated across time points were as follows: Judgment of Line Orientation (PD-NC = .47, PD-AC = .50, HOA = .59); Letter-Number Sequencing (PD-NC = .64, PD-AC = .64, HOA = .65); Semantic Fluency (PD-NC = .69, PD-AC = .89, HOA = .77); Symbol Digit Modalities Test (PD-NC = .67, PD-AC = .83, HOA = .71). For the two primary components of the Hopkins Verbal Learning Test-Revised, we found the following ICCs: immediate recall (PD-NC = .46, PD-AC = .57, HOA = .58); delayed recall (PD-NC = .42, PD-AC = .57, HOA = .54). Findings from this study provide useful information for clinicians and researchers toward selecting suitable neuropsychological tests to monitor cognition at two or more time points among newly diagnosed individuals with PD and HOA.

Age differences in inhibitory and working memory functioning: limited evidence of system interactions.

Debate persists regarding the nature of age-related deficits in inhibition, and whether inhibitory functioning depends on working memory systems. The current research aimed to measure age-related differences in inhibition and working memory, characterize the relationship between inhibitory functions and working memory performance, and determine how these relationships are affected by age. Toward these ends, we measured performance on a range of established paradigms in 60 young adults (18-30 years) and 60 older adults (60-88 years). Our findings support age-related increases in reflexive inhibition (based on the fixation offset effect and inhibition of return) and age-related decrements in volitional inhibition (based on several paradigms: antisaccade, Stroop, flanker, and Simon). This evidence of stronger reflexive inhibition combined with weaker volitional inhibition suggests that age-related deterioration of cortical structures may allow subcortical structures to operate less controlled. Regarding working memory, older adults had lower backward digit scores and lower forward and backward spatial scores. However, of the 32 analyses (16 in each age group) that tested for dependence of inhibitory functioning on working memory functioning, only one (in young adults) indicated that inhibition performance significantly depended on working memory performance. These results indicate that inhibition and working memory function largely independently in both age groups, and age-related working memory difficulties cannot account for age-related declines in inhibitory control.

This study indicates that, compared to young adults, older adults have difficulties with both working memory and volitional inhibition but show stronger reflexive inhibition.The pattern of age differences shown in this study suggests that the balance of power shifts from cortical to subcortical brain structures as we age, which may reflect cortical brain regions deteriorating more rapidly as we age, thus limiting their ability to control subcortical brain regions.In contrast to current theory, in this study the difficulties that older adults showed with volitional inhibition could not be explained by failing working memory systems, and both young and older adults showed very limited evidence that inhibitory functioning depends on working memory.

Commonalities between mind wandering and task-set switching: An event-related potential study.

Previous research has established that mind wandering does not necessarily disrupt one's task-switching performance. Here we investigated the effects of mind wandering on electrophysiological signatures, measured using event-related potentials (ERPs), during a switching task. In the current study, a final sample of 22 young adults performed a task-switching paradigm while electroencephalography was continuously recorded; mind wandering was assessed via thought probes at the end of each block. Consistent with previous research, we found no significant disruptive effects of mind wandering on task-switching performance. The ERP results showed that at the posterior electrode sites (P3, Pz, and P4), P3 amplitude was higher for mind-wandering switch trials than on-task switch trials, thus opposing the typical pattern of P3 attenuation during periods of mind wandering relative to on-task episodes. Considering that increased P3 amplitude during higher-order switch trials (e.g., response rule switching) may reflect the implementation of new higher-order task sets/rules, the current findings seem to indicate similar executive control processes underlie mind wandering and task-set switching, providing further evidence in favor of a role for switching in mind wandering.

Reconceptualizing mind wandering from a switching perspective.

Mind wandering is a universal phenomenon in which our attention shifts away from the task at hand toward task-unrelated thoughts. Despite it inherently involving a shift in mental set, little is known about the role of cognitive flexibility in mind wandering. In this article we consider the potential of cognitive flexibility as a mechanism for mediating and/or regulating the occurrence of mind wandering. Our review begins with a brief introduction to the prominent theories of mind wandering-the executive failure hypothesis, the decoupling hypothesis, the process-occurrence framework, and the resource-control account of sustained attention. Then, after discussing their respective merits and weaknesses, we put forward a new perspective of mind wandering focused on cognitive flexibility, which provides an account more in line with the data to date, including why older populations experience a reduction in mind wandering. After summarizing initial evidence prompting this new perspective, drawn from several mind-wandering and task-switching studies, we recommend avenues for future research aimed at further understanding the importance of cognitive flexibility in mind wandering.

Emotional information processing in young and older adults: meta-analysis reveals faces elicit distinct biases.

Although a number of empirical studies have found support for distinct emotional information processing biases in young versus older adults, it remains unclear whether these biases are driven by differential processing of positive or negative emotional information (or both) and whether they are moderated by stimulus type, in particular face versus non-face, the former of which is known to be subject to distinct processing. To address these gaps in the literature, our analyses included 2237 younger (mean age = 21.61 years) and 2136 older (mean age = 70.58 years) adults from 73 data sets, 19 involving face stimuli and 54 involving non-face stimuli (objects or scenes). Our findings indicated a significant overall age-related positivity effect (Hedge's g = 0.35) when comparing positive and negative stimuli, but consideration of emotionally neutral stimuli revealed significant age differences in emotional processing for negative stimuli only, with younger adults showing a stronger negativity bias. Furthermore, compared to emotionally neutral stimuli, both younger and older adults showed evidence of biases toward non-face positive and negative stimuli and toward positive but not negative face stimuli. Thus, although the present meta-analysis found evidence of an overall age-related positivity effect consistent with a shift toward positivity with aging, a different picture emerged when comparing emotional against neutral stimuli, and consideration of stimulus type revealed a distinct pattern for face stimuli, which may reflect the biological and social significance of facial expressions. Supplementary Information: The online version contains supplementary material available at 10.1007/s10433-021-00676-w.

Cognitive Functioning of Unaffected First-degree Relatives of Individuals With Late-onset Alzheimer's Disease: A Systematic Literature Review and Meta-analysis.

First-degree relatives of individuals with late-onset Alzheimer's disease (LOAD) are at increased risk for developing dementia, yet the associations between family history of LOAD and cognitive dysfunction remain unclear. In this quantitative review, we provide the first meta-analysis on the cognitive profile of unaffected first-degree blood relatives of LOAD-affected individuals compared to controls without a family history of LOAD. A systematic literature search was conducted in PsycINFO, PubMed /MEDLINE, and Scopus. We fitted a three-level structural equation modeling meta-analysis to control for non-independent effect sizes. Heterogeneity and risk of publication bias were also investigated. Thirty-four studies enabled us to estimate 218 effect sizes across several cognitive domains. Overall, first-degree relatives (n = 4,086, mean age = 57.40, SD = 4.71) showed significantly inferior cognitive performance (Hedges' g = -0.16; 95% CI, -0.25 to -0.08; p < .001) compared to controls (n = 2,388, mean age = 58.43, SD = 5.69). Specifically, controls outperformed first-degree relatives in language, visuospatial and verbal long-term memory, executive functions, verbal short-term memory, and verbal IQ. Among the first-degree relatives, APOE ɛ4 carriership was associated with more significant dysfunction in cognition (g = -0.24; 95% CI, -0.38 to -0.11; p < .001) compared to non-carriers (g = -0.14; 95% CI, -0.28 to -0.01; p = .04). Cognitive test type was significantly associated with between-group differences, accounting for 65% (R23 = .6499) of the effect size heterogeneity in the fitted regression model. No evidence of publication bias was found. The current findings provide support for mild but robust cognitive dysfunction in first-degree relatives of LOAD-affected individuals that appears to be moderated by cognitive domain, cognitive test type, and APOE ɛ4.

Spontaneous mind-wandering tendencies linked to cognitive flexibility in young adults.

Despite that previous studies have investigated mind wandering using task-switching paradigms, the association between the tendency to mind wander and cognitive flexibility remains largely unexplored. The present study investigated the relationship between self-reported spontaneous mind-wandering tendencies and task-switching performance in young adults. Seventy-nine university students performed a forced task-switching and a voluntary task-switching paradigm and then completed a battery of questionnaires. The results showed that compared to participants with lower spontaneous mind-wandering tendencies, participants with higher spontaneous mind-wandering tendencies demonstrated better performance (evidenced by smaller switch cost reaction times) in the forced task-switching paradigm despite indicating more mind wandering during task performance. Performance on the voluntary task-switching paradigm, on the other hand, did not differ between the two groups. The findings in the forced task-switching paradigm indicate a link between mind wandering and cognitive flexibility, thus providing initial evidence in favor of a role for switching in mind wandering.

Forward and backward spatial recall in Parkinson's disease and matched controls: A 1-year follow-up study.

Patients with Parkinson's disease (PD) exhibit a domain-general visuospatial dysfunction; however, no previous study has examined changes over time in forward and backward spatial recall in PD against controls. To evaluate changes in short-term (STM) and working memory (WM) dysfunction in PD, the current study assessed performance on a computer-modified version of the Corsi Block-Tapping Test (forward and backward recall) at two-time points 1 year apart, while simultaneously exploring associations with potentially relevant demographic and clinical variables. We enrolled 38 patients with PD and 38 controls matched for age, sex, and Montreal Cognitive Assessment (MoCA) total scores. Linear mixed-effects models analyzed the primary measured variables (forward and backward scores). At baseline, the dysfunction effect sizes were as follows: forward recall (-0.45, 95% CI [-0.90, 0.01]) and backward recall (-0.26, 95% CI [-0.71, 0.19]). At follow-up, patients exhibited substantially greater difficulties in backward recall (-0.65, 95% CI [-1.18, -0.13]) compared to the baseline assessment, whereas the forward dysfunction effect size remained almost the same (-0.43, 95% CI [-0.94, 0.09]). Age (p = .005, f = 0.35) and total scores on MoCA (p = .017, f = 0.18), irrespective of group and recall condition, were significant predictors of spatial block scores. The pattern of dysfunction effect sizes indicates that, in contrast to forward recall, backward recall dysfunction in PD worsened 1-year after the baseline assessment, presumably reflecting the progression of PD-related visuospatial WM dysfunction.

Effects of a Brief Stair-Climbing Intervention on Cognitive Functioning and Mood States in Older Adults: A Randomized Controlled Trial.

Despite an abundance of evidence that exercise benefits cognition and mood, physical activity levels among older adults remain low, with time and inaccessibility posing major barriers. Interval stair climbing is an accessible time-efficient form of physical activity demonstrated to benefit cognition and mood in young adults, but effectiveness in older adults remains unknown. To address this, 28 older adults (Mage = 69.78 years, 16 females) undertook cognitive and mood assessments twice, 1 week apart, once preceded by interval stair climbing. A fairly large, albeit only marginally significant, effect size (ηp2=.12) indicated improved cognition following the moderate- to high-intensity intervention; however, rather than improving mood, older adults reported feeling more tired (g = 0.51). These outcomes provide initial indications that this mode of exercise that can easily translate to naturalistic settings offers promise as an intervention strategy, but more research is needed to optimize the protocol to suit aged populations (ACTRN1261900169014).

Short-Term Retest Performance in Young versus Older Adults: Consideration of Integrated Speed-Accuracy Measures.

OBJECTIVES: The current research addressed gaps in the literature regarding short-term computerized cognitive retest performance in young and older adults using two integrated speed-accuracy metrics. The aims were: (a) to advance the aging literature on short-term retest performance using a computerized cognitive battery and a retest schedule that included both within- and between-day time points, and (b) to assess the test-retest reliability of two integrated speed-accuracy metrics, inverse efficiency scores (IES) and balanced integration scores (BIS). METHOD: Twenty young (18-23 years) and thirty older (65-71 years) men completed a battery measuring a range of cognitive functions, six times over three testing days, each 1 week apart. RESULT: Compared to young adults, older adults exhibited steeper within- and between-day performance gains in IES and BIS, which may reflect a combination of lower initial cognitive ability and familiarity, indicating that older adults may require more familiarization on computerized tests. Relative to unadjusted reaction times, IES reliability appeared comparable in older adults, but slightly lower among young adults. The reliability of BIS was lower than unadjusted reaction times and IES in both age groups. DISCUSSION: Our findings provide guidance for researchers wanting to combine speed and accuracy into a single performance metric in repeated testing contexts.

Bidirectional Within- and Between-Person Relations Between Physical Activity and Cognitive Function.

OBJECTIVES: To examine bidirectional within- and between-person relations between physical activity and cognitive function across 15 years. METHODS: Participants (N = 1,722, age range 40-85 years, 55% women) were drawn from the Betula prospective cohort study. We included 4 waves of data. Bivariate latent curve models with structured residuals were estimated to examine bidirectional within- and between-person relations between physical activity and cognitive function (episodic memory recall, verbal fluency, visuospatial ability). RESULTS: We observed no statistically significant bidirectional within-person relations over time. Higher levels of physical activity at baseline were related to less decline in episodic memory recall. Positive occasion-specific within- and between-person relations were observed, with the most consistent being between physical activity and episodic memory recall. DISCUSSION: The lack of bidirectional within-person relations indicates that shorter time lags may be needed to capture time-ordered within-person relations. The link between higher physical activity at baseline and less decline in episodic memory recall over time may indicate a protective effect of physical activity on episodic memory recall.

A Comprehensive Meta-analysis on Short-term and Working Memory Dysfunction in Parkinson's Disease.

A previous meta-analysis demonstrated short-term memory (STM) and working memory (WM) dysfunction in patients with Parkinson's disease (PD). However, considerable research on the topic that calls into question the extent of such impairments in PD has since been published. The aim of the present quantitative review was to provide the largest statistical overview on STM and WM dysfunction in Parkinson's disease (PD), while simultaneously providing novel insights on moderating factors of effect size heterogeneity in PD. The systematic literature search in PubMed, PsycINFO, PsycArticles, Scopus and Web of Science databases allowed us to estimate 350 effect sizes from 145 empirical studies that reported STM and WM scores for patients with PD against healthy controls. The outcomes indicated general dysfunction in the visuospatial domain and poor verbal WM in PD. Subgroup analyses suggested that mild cognitive impairment is associated with STM and WM difficulties in PD. Furthermore, meta-regression analyses revealed that disease duration accounted for more than 80% of the visuospatial STM effect size variance (ß = 0.136, p < .001, R2 = .8272), larger daily levodopa equivalent dose was associated with WM dysfunction (verbal: ß = -0.001, p = .016, R2 = .1812; visuospatial: ß = 0.003, p = .069, R2 = .2340), and years of education partially explained the verbal STM effect size variance (ß = -0.027, p = .040, R2 = .1171). Collectively, these findings advance our understanding of underlying factors that influence STM and WM functioning in PD, while at the same time providing novel directions for future research.

Volunteering in older adulthood is associated with activity engagement and cognitive functioning.

Introduction: Given evidence that activity engagement in older adulthood can have protective effects on the aging brain, we investigated the idea that volunteering in the community, which often encompasses social, cognitive, and physical activity, might benefit cognition. Method: Ninety-one retired 65- to 75-year-olds reported their sociodemographic characteristics, wellbeing, volunteering, and activity engagement. They also completed computerized cognitive tests that tapped specific functions known to decline disproportionately with age. Results: Volunteering at least monthly was associated with better working memory and more social and cognitive activity. Mediation analyses indicated that volunteering was indirectly related to switching performance via cognitive activity. However, the volunteering-working memory association did not depend on activity engagement, leaving the underpinning mechanisms unclear. Conclusions: These findings provide new insight into positive associations between older people's volunteering, activity engagement, and cognitive functioning. However, further work is needed to understand the mechanisms that drive volunteering-cognition links, and to establish causality.

Physical activity and cognitive function: between-person and within-person associations and moderators.

In the present study, we decomposed between- and within-person effects and examined moderators of the longitudinal physical activity-cognition association. Participants (N = 1722) were drawn from the Betula study and we included four waves of data across 15 years. Bayesian multilevel modeling showed that self-reported physical activity did not predict changes in cognitive function. Physical activity positively predicted cognitive performance at baseline, and the relations were stronger for more active (compared to less active) older adults. Physical activity had a positive within-person effect on cognitive function. The within-person effect of physical activity on episodic memory recall was stronger for participants who on average engaged in less physical activity. The within-person effect on verbal fluency was stronger for participants with more education. Our results suggest that preserving cognitive functioning in old age might be more a matter of what you do in old age than reflecting what you did earlier in life.

Acute exercise-related cognitive effects are not attributable to changes in end-tidal CO2 or cerebral blood velocity.

PURPOSE: Cognition, cerebral blood flow (CBF) and its major regulator (i.e., arterial CO2), increase with submaximal exercise and decline with severe exercise. These responses may depend on fitness. We investigated whether exercise-related changes in cognition are mediated in part by concomitant changes in CBF and CO2, in ten active (26 ± 3 years) and ten inactive (24 ± 6 years) healthy adults. METHODS: Participants completed two randomised sessions; exercise and a resting CO2-control-wherein end-tidal CO2 (PETCO2) was matched between sessions and clamped across conditions at exercise-associated increases (+ 3 mmHg) and hypercapnia (+ 10 mmHg). Exercise comprised inclined walking at submaximal and severe intensities. CBF was indexed using right middle cerebral artery blood velocity (MCAv). Cognition (visuomotor, switching and inhibitory response time) was measured before, during, and after exercise. RESULTS: MCAv and its inverted-U response to exercise were comparable between groups, whereas visuomotor performance improved during submaximal exercise in the active group only (p = 0.046). Submaximal, but not severe (p = 0.33), exercise increased MCAv (p ≤ 0.03). Hypercapnia increased MCAv during the CO2-control (27 ± 12%) and during submaximal exercise (39 ± 17%; p < 0.01). Despite the acute increases in MCAv, cognition was impaired during both levels of increased PETCO2 (3-6%; p ≤ 0.04), regardless of session. Overall, resting or exercise-related changes in PETCO2 and MCAv did not associate with changes in cognition (r ≤ 0.29 ± 0.34). Fitness ([Formula: see text]O2MAX) was associated with baseline cognition (r ≥ 0.50). CONCLUSION: Acute increases in PETCO2 and MCAv were not associated with improved cognition. In fact, cognitive performance was impaired at both levels of increased PETCO2, regardless of session. Finally, fitter people were found to have better cognition.

A meta-analysis on verbal working memory in children and adolescents with ADHD.

Objective: Previous meta-analyses have demonstrated verbal working memory (WM) dysfunction in children and adolescents with attention deficit/hyperactivity disorder (ADHD); however, the findings are inconsistent. The main objective of this meta-analysis was to investigate the performance of children and adolescents with ADHD in the Digit Span Backwards (DSB) subtest from the Wechsler Intelligence Scale for Children or Wechsler Adult Intelligence Scale. We also sought to provide an updated meta-analysis on WM in children and adolescents with ADHD.Method: PubMed, PsyINFO, Scopus, and Web of Science were searched to locate studies published between 1990 and 2016 that report DSB scores both of children and adolescents with ADHD and matched controls. Potential moderator variables were also analyzed.Results: Forty-nine studies comparing children and adolescents with ADHD (n = 4956) against healthy controls (n = 3249) generated a medium-sized effect (Hedges' g) of 0.56 (95% CI [0.49, 0.64]), indicating poorer verbal WM performance in those with ADHD. A subgroup meta-analysis of studies with participants aged 8-16 years only demonstrated low heterogeneity (I2 = 17.06, cf. 55.50 for the main analysis). Moreover, the meta-regression showed a negative association (ß = -.05, p = .02) between DSB performance differences and increasing age, indicating that for every one year increase in age the effect size decreased by .05.Conclusion: These results, which emanated from the largest meta-analysis concerning verbal WM in ADHD reported to date, reinforce WM as a key domain of cognitive dysfunction in ADHD, and point to age as the main variable influencing DSB performance difficulties.

Effects of a Brief Stair-Climbing Intervention on Cognitive Performance and Mood States in Healthy Young Adults.

OBJECTIVE: Previous studies focused on the benefits of acute exercise on cognition and mood have mostly used specialized laboratory-based equipment, thus little is known about how such protocols generalize to naturalistic settings. Stair climbing is a simple and readily accessible means of exercise that can be performed in naturalistic settings (e.g., at home or at the workplace). In the present study we examined the effects of stair-climbing intervals on subsequent cognitive performance and mood in healthy young adults. METHOD: Thirty-two undergraduate students (M age = 19.4 years, SD = 1.3; 21 females) completed a controlled randomized crossover trial with session order counterbalanced across participants. Participants visited the lab on two occasions, one week apart, and completed one control session (no exercise) and one stair-climbing session (3 × 1 min stair-climbing intervals) with cognitive performance and mood assessed at the end of each session. RESULTS: Repeated measures ANCOVA revealed that males (Hedges' g av = 0.45) showed better switching performance following the stair climbing but females (Hedges' g av < 0.03) did not. Participants felt more energetic (Hedges' g av = 1.05), less tense (Hedges' g av = 0.61), and less tired (Hedges' g av = 0.43) following the stair climbing. In addition, higher exercise intensity during the stair climbing predicted better subsequent switching performance and higher energetic ratings. CONCLUSION: These findings indicate that short bouts of stair climbing in a naturalistic setting can induce cognitive benefits for more challenging tasks, albeit only in males, indicating a sex-specific effect. Short bouts of stair climbing can be a practical approach to increase feelings of energy in daily life.

Swimming-related effects on cerebrovascular and cognitive function.

Both acute and regular exercise influence vascular and cognitive function. Upright aquatic exercise increases mean middle cerebral artery blood velocity (MCAvmean ) and has been suggested as favorable for cerebrovascular adaptations. However, MCAvmean has not been reported during swimming. Thus, we examined the cerebrovascular and cognitive effects of swimming. Ten land-based athletes (22 ± 5 years) and eight swimmers (19 ± 1 years) completed three cognitive tasks and four conditions that were used to independently and collectively delineate the swimming-related factors (i.e., posture, immersion, CO2 retention [end-tidal CO2 ; PETCO2 ], and motor involvement). Measurements of MCAvmean and PETCO2 were taken throughout each condition. Prone posture increased MCAvmean by 11% (P < 0.01 vs. upright land). Water immersion independently increased MCAvmean when upright (12%; P < 0.01) but not prone (P = 0.76). The consequent rise in PETCO2 during head-out, breast-stroke swimming (50% heart rate range) independently increased MCAvmean by 14% (P < 0.01), while the motor involvement of swimming per se did not significantly change MCAvmean (P = 0.32). While accounting for sex, swimmers had ~17% lower MCAvmean during all rest conditions (P ≤ 0.05). However, in a subset of participants, both groups had similar internal carotid artery diameters (P = 0.99) and velocities (P = 0.97). Water immersion per se did not alter cognition (P ≥ 0.15), but 20 min of moderate-intensity swimming improved visuomotor performance by 4% (P = 0.03), regardless of athlete group (P = 0.12). In conclusion, breast-stroke swimming increased MCAvmean mostly due to postural and PETCO2 effects, with minimal contributions from water immersion or motor activity. Lastly, swimming improved cognitive functioning acutely, regardless of athlete group. Future research should explore the chronic effects of swimming on cerebrovascular function and cognition, particularly in aging.

Cerebrovascular regulation is not blunted during mental stress.

NEW FINDINGS: What is the central question of the study? What are the effects of acute mental stress on the mechanisms regulating cerebral blood flow? What is the main finding and its importance? The major new findings are as follows: (i) high mental stress and hypercapnia had an interactive effect on mean middle cerebral artery blood velocity; (ii) high mental stress altered the regulation of cerebral blood flow; (iii) the increased cerebrovascular hypercapnic reactivity was not driven by changes in mean arterial pressure alone; and (iv) this increased perfusion with mental stress appeared not to be justified functionally by an increase in oxygen demand (as determined by near-infrared spectroscopy-derived measures). ABSTRACT: In this study, we examined the effects of acute mental stress on cerebrovascular function. Sixteen participants (aged 23 ± 4 years; five female) were exposed to low and high mental stress using simple arithmetic (counting backwards from 1000) and more complex arithmetic (serial subtraction of 13 from a rapidly changing four-digit number), respectively. During consecutive conditions of baseline, low stress and high stress, end-tidal partial pressure of CO2 ( PET,CO2 ) was recorded at normocapnia (37 ± 3 mmHg) and clamped at two elevated levels (P < 0.01): 41 ± 1 and 46 ± 1 mmHg. Mean right middle cerebral artery blood velocity (MCAvmean ; transcranial Doppler ultrasound), right prefrontal cortex haemodynamics (near-infrared spectroscopy) and mean arterial blood pressure (MAP; finger photoplethysmography) were measured continuously. Cerebrovascular hypercapnic reactivity (ΔMCAvmean /Δ PET,CO2 ), cerebrovascular conductance (CVC; MCAvmean /MAP), CVC CO2 reactivity (ΔCVC/Δ PET,CO2 ) and total peripheral resistance (MAP/cardiac output) were calculated. Acute high mental stress increased MCAvmean by 7 ± 7%, and more so at higher PET,CO2 (32 ± 10%; interaction, P = 0.03), illustrating increased sensitivity to CO2 (i.e. its major regulator). High mental stress also increased MAP (17 ± 9%; P ≤ 0.01), coinciding with increased near-infrared spectroscopy-derived prefrontal haemoglobin volume and saturation measures. High mental stress elevated both cerebrovascular hypercapnic and conductance reactivities (main effect of stress, P ≤ 0.04). These findings indicate that the cerebrovascular response to acute high mental stress results in a coordinated regulation between multiple processes.