Under pressure-the influence of hypergravity on electrocortical activity and neurocognitive performance.

The effects of hypergravity and the associated increased pressure on the human body have not yet been studied in detail, but are of great importance for the safety of astronauts on space missions and could have a long-term impact on rehabilitation strategies for neurological patients. Considering the plans of international space agencies with the exploration of Mars and Moon, it is important to explore the effects of both extremes, weightlessness and hypergravity. During parabolic flights, a flight manoeuvre that artificially creates weightlessness and hypergravity, electrocortical activity as well as behavioural parameters (error rate and reaction time) and neuronal parameters (event-related potentials P300 and N200) were examined with an electroencephalogram. Thirteen participants solved a neurocognitive task (mental arithmetic task as a primary task and oddball paradigm as a secondary task) within normal as well as hypergravity condition in fifteen consecutive parabolas for 22 s each. No changes between the different gravity levels could be observed for the behavioural parameters and cortical current density. A significantly lower P300 amplitude was observed in 1 G, triggered by the primary task and the target sound of the oddball paradigm. The N200, provoked by the sounds of the oddball paradigm, revealed a higher amplitude in 1.8 G. A model established by Kohn et al. (2018) describing changes in neural communication with decreasing gravity can be used here as an explanatory approach. The fluid shift increases the intracranial pressure, decreases membrane viscosity and influences the open state probability of ion channels. This leads to an increase in the resting membrane potential, and the threshold for triggering an action potential can be reached more easily. The question now arises whether the observed changes are linear or whether they depend on a specific threshold.

The influence of microgravity on cerebral blood flow and electrocortical activity.

Changes in gravity conditions have previously been reported to influence brain hemodynamics as well as neuronal activity. This paper attempts to identify a possible link between changes in brain blood flow and neuronal activity during microgravity. Middle cerebral artery flow velocity (MCAv) was measured using Doppler ultrasound. Brain cortical activity (i.e., cortical current density) was measured using electroencephalography. Finger blood pressure was recorded and exported to generate beat-by-beat systolic (SBP), diastolic (DBP) and mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), and cerebrovascular conductance index (CVCi). Seventeen participants were evaluated under normal gravity conditions and microgravity conditions, during 15 bouts of 22-s intervals of weightlessness during a parabolic flight. Although MAP decreased and CO increased, MCAv remained unchanged in the microgravity condition. CVCi as the quotient of MCAv and MAP increased in microgravity. Cortical current density showed a global decrease. Our data support earlier data reporting a decrease in the amplitude of event-related potentials recorded during microgravity. However, the general decrease in neural excitability in microgravity seems not to be dependent on hemodynamic changes.

Distraction versus Intensity: The Importance of Exercise Classes for Cognitive Performance in School.

OBJECTIVE: The aim of this study was to compare the influence of a class of aerobic exercise and an art class on brain cortical activity and possible effects on cognitive performance. SUBJECT AND METHODS: Electroencephalography was used to record the electrocortical activity of 16 schoolchildren (8-10 years old) before and after an aerobic exercise class and an art class. Performance in a standardized test of educational attainment (VERA-3) was assessed following both classes. RESULTS: A significant decrease in cortical activity was detected in all 4 lobes after exercise but not after art classes (p < 0.05). No changes in cognitive performance were observed after exercise and art classes. CONCLUSION: In this study, cortical activity was reduced after an exercise class but no effect on cognitive performance was observed. Hence, the neurophysiological effect of exercise should be further evaluated regarding different kinds of cognitive performance: creativity, knowledge acquisition as well as the outlasting effects of exercise on academic achievement.

The effect of 6 h of running on brain activity, mood, and cognitive performance.

Long-duration exercise has been linked with the psychological model of flow. It is expected that the flow experience is characterized by specific changes in cortical activity, especially a transient hypofrontality, which has recently been connected with an increase in cognitive performance post-exercise. Nevertheless, data on neuro-affective and neuro-cognitive effects during prolonged exercise are rare. The cognitive performance, mental state, flow experience, and brain cortical activity of 11 ultramarathon runners (6 female, 5 male) were assessed before, several times during, and after a 6-h run. A decrease in cortical activity (beta activity) was measured in the frontal cortex, whereas no changes were measured for global beta, frontal or global alpha activity. Perceived physical relaxation and flow state increased significantly after 1 h of running but decreased during the following 5 h. Perceived physical state and motivational state remained stable during the first hour of running but then decreased significantly. Cognitive performance as well as the underlying neurophysiological events (recorded as event-related potentials) remained stable across the 6-h run. Despite the fact that women reported significant higher levels of flow, no further gender effects were noticeable. Supporting the theory of a transient hypofrontality, a clear decrease in frontal cortex activity was noticeable. Interestingly, this had no effect on cognitive performance. The fact that self-reported flow experience only increased during the first hour of running before decreasing, leads us to assume that changes in cortical activity, and the experience of flow may not be linked as previously supposed.

Shades of gravity - effects of planetary gravity levels on electrocortical activity and neurocognitive performance.

The plans of international space agencies to return to the Moon and explore deep space, including Mars, highlight the challenges of human adaptation and stress the need for a thorough analysis of the factors that facilitate, limit and modify human performance under extreme environments. This study investigates the influence of partial gravity on behavioural (error rate and reaction time) and neuronal parameters (event-related potentials) through parabolic flights. Brain cortical activity was assessed using EEG from 18 participants who solved a neurocognitive task, consisting of a mental arithmetic task and an auditory oddball paradigm, during Earth (1G), Lunar (0.16G + 0.25G) and Martian gravity (0.38G + 0.5G) for 15 consecutive parabolas. Data shows higher electrocortical activity in Earth gravity compared to Lunar and Martian gravity in the parietal lobe. No differences in participants' performance were found among the gravity levels. Event-related potentials displayed gravity-dependent variations, though limited stimuli recording suggests caution in interpretation. Data suggests a threshold between Earth and Martian gravity within the different gravities responsible for physiological changes, but it seems to vary greatly between individuals. The altered neuronal communication could be explained with a model developed by Kohn and Ritzmann in 2018. The increasing intracranial pressure in weightlessness changes the properties of the cell membrane of neurons and leads to a depolarisation of the resting membrane potential. The findings underscore the individuality of physiological changes in response to gravity alterations, signalling the need for further investigations in future studies.

The effect of age on cerebral blood flow responses during repeated and sustained stand to sit transitions.

INTRODUCTION: Aging is associated with impaired cerebrovascular blood flow and function, attributed to reduced vasodilatory capacity of the cerebrovascular network. Older adults may also have an impaired relationship between changes in blood pressure and cerebral blood flow; however, previous reports conflict. This study aimed to compare the blood pressure and cerebral blood flow responses to both repeated and sustained stand-to-sit transitions in young and older adults, and to assess the relationship with cerebrovascular reactivity. METHODS: In 20 young (age: 24 ± 4 years) and 20 older (age: 71 ± 7 years) adults we compared middle cerebral artery flow velocity (MCAv), end-tidal partial pressure of carbon dioxide (PET CO2 ), and blood pressure (mean arterial blood pressure [MAP]) during repeated stand-to-sit (10 s standing and 10 s sitting) and sustained stand-to-sit (3 min standing followed by 2 min sitting) transitions. Cerebrovascular reactivity to changes in carbon dioxide levels was assessed using a repeated breath-hold test. RESULTS: The % change in MCAv per % change in MAP (%∆MCAv/%∆MAP) was higher in the older adults than in the young adults during repeated stand-to-sit transitions. During the sustained protocol the %∆MCAv/%∆MAP response was similar in both age groups. A high %∆MCAv/%∆MAP response during the repeated stand-to-sit protocol was associated with low cerebrovascular reactivity to CO2 (r = -.39; p < .01), which was significantly lower in the older adults. CONCLUSION: These findings suggest that the higher %∆MCAv/%∆MAP during repeated stand-sit transitions was associated with impaired cerebrovascular reactivity. Impairments in endothelial function and vascular stiffness with age may contribute to the altered transient cerebral pressure-flow responses in older adults.

Rating of perceived exertion - a valid method for monitoring light to vigorous exercise intensity in individuals with subjective and mild cognitive impairment?

In rehabilitation settings, exercise intensity is often monitored with Borg's rating of perceived exertion (RPE). However, previous studies showed that severe cognitive impairment may limit the usability of the RPE. The aim of this study was to assess the relationship between RPE and heart rate (HR), and to establish whether a target RPE can be used to achieve exercise intensity based on an individual's HR-RPE in people with early cognitive impairment. 97 participants (74.7 ± 6 years) with early cognitive impairment completed an incremental exercise test. Of these, 54 were tested during a single, RPE guided exercise session. RPE and HR were monitored throughout. Correlations between HR and RPE were assessed using Spearman's correlation. Mean differences between measured HR and target HR were calculated and compared using a two-way ANOVA with factors cognition and exercise mode. Bland-Altman plots were constructed to analyse the agreement between target and measured HR. HR and RPE correlated moderately with each other (p < 0.001; r = 0.555) and no differences between target and measured HR were observed. Bland-Altman plots revealed a mean difference of 1.2 bpm and a 95% level of agreement was between 24.4 and -22.1 bpm. No differences in rating accuracy were observed between different cognitive impairment levels nor between different exercise modes. Bland-Altman plots revealed some variance between the participants with almost half of them missing target HR by 10bpm or more. Therefore, the RPE should only be applied with caution and, if possible, with other measurements (e.g. heart rate monitors) to ensure that target intensity is reached.

Transient cerebral blood flow responses during microgravity.

PURPOSE: A number of studies has well described central cardiovascular changes caused by changing gravity levels as they occur e.g. during parabolic flight. limited data exists describing the effect of microgravity on the cerebrovascular system and brain perfusion. METHODS: In this study middle cerebral artery velocity (MCAv) of 16 participants was continuously monitored on a second-by-second basis during 15 consecutive parabolas (1G, 1,8G, 0G, 1,8G) using doppler ultrasound. Simultaneously central cardiovascular parameters (heart rate, mean arterial blood pressure, cardiac output) were assessed. RESULTS: Results revealed an immediate reaction of central cardiovascular parameters to changed gravity levels. In contrast, changes in MCAv only initially were in accordance with a normal cerebral autoregulation. Whereas all of the measured central cardiovascular parameters seemed to have reached a steady state after approximately 8 s of microgravity, MCAv, after an initial decrease with the onset of microgravity, increased again during the second half of the microgravity phase. CONCLUSION: It is concluded that this increase in MCAv during the second half of the microgravity period reflects a decrease of cerebrovascular resistance caused by a pressure driven increased venous outflow and/or a contraction of precapillary sphincters in order to avoid hyperperfusion of the brain.

Validation of a widely used heart rate monitor to track steps in older adults.

BACKGROUND: Activity tracking devices gain popularity in research, which is due to their multiple features (e.g. heart rate monitor, step count) and easy handling. Nevertheless, many devices used for research are lacking validation of specific features. This study aimed to assess the validity of the Polar M400© activity tracker to count steps in older adults and, therefore, compared it to a previously validated pedometer (Omron Walking Style©) and observed step count. METHODS: Thirty-two older adults (mean age: 74.8±5.9 years) walked at a self-selected, normal gait speed on a tartan track for 200 meters while wearing the activity tracker and the pedometer. Additionally, steps were counted manually. Data was analysed using Kruskal-Wallis test and Lin's concordance coefficient. Furthermore, Bland Altman plots were employed to evaluate accuracy of the activity tracker. RESULTS: Kruskal-Wallis test revealed significant differences between the step count of the activity tracker and the pedometer (P=0.011) but no further differences were observed. Lin's concordance showed a moderate correlation between activity tracker and pedometer (rc=0.561) and between pedometer and observed step count (rc=0.690). A high correlation was detected between activity tracker and observed step count (rc=0.802). Bland Altman plots revealed good accuracy of the activity tracker. CONCLUSIONS: The Polar M400© activity tracker accurately assesses steps during walking in older adults. Nevertheless, a slight overestimation compared to the pedometer was observed, which should be considered when using the activity tracker for tracking steps over a longer period of time.

Neurocognitive performance is enhanced during short periods of microgravity-Part 2.

Previous studies showed a decrease in reaction time during the weightlessness phase of a parabolic flight. This effect was found to be stronger with increasing task complexity and was independent of previous experience of weightlessness as well as anti-nausea medication. Analysis of event related potentials showed a decreased amplitude of the N100-P200 complex in weightlessness but was not able to distinguish a possible effect of task complexity. The present study aimed to extend this previous work, by comparing behavioral (reaction time) and neurological (event related potentials analysis) performance to a simple (oddball) and a complex (mental arithmetic + oddball) task during weightlessness. 28 participants participated in two experiments. 11 participants performed a simple oddball experiment in the 1G and 0G phases of a parabolic flight. 17 participants were presented a complex arithmetic task in combination with an oddball task during the 1G and 0G phases of a parabolic flight. Reaction time as well as event related potentials (ERP) were assessed. Results revealed a reduced reaction time (p < .05) for the complex task during 0G. No gravity effects on reaction time were found for the simple task. In both experiments a reduction of typical ERP amplitudes was noticeable in weightlessness. It is assumed that the weightlessness induced fluid shift to the brain is positively affecting neuro-behavioral performance.

Short Bouts of Intensive Exercise During the Workday Have a Positive Effect on Neuro-cognitive Performance.

Beside its positive impact on physical health, exercise is indicated to positively affect cognitive performance based on a relocation of cortical activity. This study examined the influence of different types of breaks on cognitive performance and related cortical activity in office-based employees. Breaks were filled with exercise, resting or a usual break and a control condition where employees continued working without any break. Cognitive performance was assessed using the d2-R test and two commercially available cognitive tasks. Brain cortical activity was recorded using electroencephalography before and after breaks. Individual's mood was analysed using a profile of mood state. Results indicate a positive effect of a 3-min boxing intervention on cognitive performance, mirrored by a decrease in prefrontal cortex activity. Although perceived psychological state was increased after the usual break, this is reflected in neither cortical activity nor cognitive performance. With respect to the fact that also bike activity resulted an increase in prefrontal alpha-2 activity, a positive effect of exercise on neuro-cognitive performance can be stated. Health and economic benefits may result from brief physical activity breaks and help to maintain workplace performance and job satisfaction. Copyright © 2015 John Wiley & Sons, Ltd.

Neuro-cognitive performance is enhanced during short periods of microgravity.

There is increasing interest in the effects of microgravity on cognitive processing, particularly as it relates to the potential for human space travel. While findings to date are quite inconsistent, studies reporting a decrement in cognitive performance have generally not been able to distinguish between the direct influence of microgravity, and any associated influence of stress. Furthermore, the currently available findings are primarily based on behavioral observations, and there is a need to better understand the underlying neurophysiological responses. The current study aimed to determine the effects of microgravity on neurophysiological processing during a mental arithmetic task (executive function). During the normal- and microgravity phases of a parabolic flight, four levels of a mental arithmetic task were presented on a touchscreen tablet. The latency between the appearance of the problem and the participants' response was identified as reaction time. In addition visual evoked potentials N1 and P2 were determined using an active EEG system and analyzed using source localization algorithms. Results showed an increase in reaction time with increasing levels of task difficulty. During the most complex levels, reaction time was significantly reduced during microgravity. This observation was independent of previous parabolic flight experience as well as the use of anti-motion-sickness medication. P2 amplitude decrease during microgravity was concomitant to a related involvement of the superior frontal and medial frontal gyrus. It is concluded that cortical processes are enhanced during microgravity, and that previously reported impairments in cognitive performance are likely attributable to increased stress rather than weightlessness itself.