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Long-term isolation has been reported to have impact on psycho-physiological performance in humans. As part of the 520 days isolation study (MARS500, n=6) from June 3rd 2010 to November 4th 2011, this study aimed to show that stress caused by isolation and confinement is mirrored in cortical activity and cortisol levels and that exercise is a valid countermeasure. Cortical activity was measured by electroencephalography (EEG) pre- and post-moderate exercise every two weeks, salivary cortisol was taken every 60 days. Data show a decrease of global cortical activity, in both alpha- and beta-activity (p<.05-p<.001), and an increase of salivary cortisol (p<.05-p<.001), during the isolation, indicating that isolation acts as a chronic stressor with impact on cortical activity and cortisol levels. Moderate exercise leads to an increase (p<.01) in cortical activity. Therefore, during long-term space missions the factor isolation must be kept in mind as the reduction of cortical activity and the heightened stress level could impair performance. However moderate exercise might be able to counteract this impairment., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Balance is a crucial component in numerous every day activities such as locomotion. Previous research has reported distinct changes in cortical theta activity during transient balance instability. However, there remains little understanding of the neural mechanisms underlying continuous balance control. This study aimed to investigate cortical theta activity during varying difficulties of continuous balance tasks, as well as examining the relationship between theta activity and balance performance. 37 subjects completed nine balance tasks with different levels of surface stability and base of support. Throughout the balancing task, electroencephalogram (EEG) was recorded from 32 scalp locations. ICA-based artifact rejection was applied and spectral power was analyzed in the theta frequency band. Theta power increased in the frontal, central, and parietal regions of the cortex when balance tasks became more challenging. In addition, fronto-central and centro-parietal theta power correlated with balance performance. This study demonstrates the involvement of the cerebral cortex in maintaining upright posture during continuous balance tasks. Specifically, the results emphasize the important role of frontal and parietal theta oscillations in balance control., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Intense exercise and sleep deprivation affect the amount of homeostatically regulated slow wave sleep in the subsequent sleep period. Since brain energy metabolism plays a decisive role in the regulation of behavioral states, we determined the concentrations of nucleotides and nucleosides: phosphocreatine, creatine, ATP, ADP, AMP, adenosine, and inosine after moderate and exhaustive treadmill exercise as well as 3 and 5 h of sleep deprivation and sleep in the rat brain using the freeze-clamp technique. High intensity exercise resulted in a significant increase of the sleep-promoting substance adenosine. In contrast, following sleep, inosine and adenosine levels declined considerably, with an accompanied increase of ADP after 3 h and ATP after 5 h. Following 3 h and 5 h sleep deprivation, ADP and ATP did not differ significantly, whereas inosine increased during the 3 and 5-h period. The concentrations of AMP, creatine and phosphocreatine remained unchanged between experimental conditions. The present results are in agreement with findings from other authors and suggest that depletion of cerebral energy stores and accumulation of the sleep promoting substance adenosine after high intensity exercise may play a key role in homeostatic sleep regulation, and that sleep may play an essential role in replenishment of high-energy compounds.

Implications of exercise on serotonergic neuromodulation in the brain have been investigated in two studies. Acute paroxetine (selective serotonin (5-HT) reuptake inhibitor) administration to endurance athletes, who performed a cycle ergometer test to exhaustion at moderate intensity, reduced time to exhaustion and post exercise cognitive performance in comparison to trials with placebo or BCAA administration. Furthermore, during a 3-week moderate endurance training of sedentary males basaline values of Bmax of 5-HT transporters (5-HTT) and 5-HT2A receptors (5-HT(2A)R) on isolated platelet membranes increased while plasma prolactin (PRL) concentrations decreased as well as mood and physical efficiency improved. In contrast, after an excessive training program over four weeks, well-trained endurance athletes showed no change of Bmax of 5-HTT, but a decline of 5-HT(2A)R density and an increase in basal plasma PRL concentration. Mood was impaired and central fatigue increased. Thus, the impact of exercise on 5-HT neurotransmission may depend on training state of athletes and extent of exertion. The theoretical background of the implication of exercise and the effect of long lasting exhaustive exercise in athletes on mental and physical efficiency or central fatigue are evaluated. The significance of the primary disturbance of central neuromodulation and dysfunction of 5-HTT, 5-HT receptor subtypes and the phosphoinositol signal transduction as well as the limited modulation capacity of the 5-HT system in overstrain are also addressed.

Modern technical and biochemical methods allow investigation of hemodynamic and metabolic responses of the human brain during muscular work. Following a general introduction to the topic results from selected studies on endogenous opioid peptides, pain sensitivity and psyche, regional cerebral blood flow and cerebral glucose metabolism, amino acid transport across the blood-brain barrier, impact of physical work on the serotonergic system, influence of oxygen partial pressure on neurotransmitters and hormones during exercise, role of the brain as performance limiting factor as well as age-related changes in cerebral blood flow and hypothalamo-pituitary-adrenal/-gonadal axis function will be presented.