Endurance exercise selectively impairs prefrontal-dependent cognition

Neuroelectric and behavioral indices of interference control during acute cycling

OBJECTIVE

This study examined the effects of in-task, moderate-intensity aerobic exercise on neuroelectric and behavioral indices of interference control, one component of executive control.

METHODS

Forty-one participants completed a V O(2) max test to determine maximal heart rate (HR). On a separate day, event-related brain potentials and task performance were measured during the counterbalanced conditions of upright cycling at 60% of maximal HR and rest while performing congruent and incongruent trials of a flanker task.

RESULTS

Exercise resulted in reduced response accuracy for incongruent trials relative to rest; an effect not found for congruent trials. Decreased N1 amplitude was observed during exercise at parietal sites and globally for N2. Exercise also resulted in increased amplitude for the P2 at frontal and central sites, and for the P3 at frontal and lateral sites. Further, longer N2 and P3 latencies were observed during exercise relative to rest.

CONCLUSION

These findings suggest that the need to allocate attentional resources toward the large-scale bodily movements inherent in exercise may relate to inefficiency of neural resource allocation, resulting in decreased interference control.

SIGNIFICANCE

These data indicate general and selective exercise-induced decrements in cognitive processing while performing acute aerobic exercise.

Transient hypofrontality as a mechanism for the psychological effects of exercise

Although exercise is known to promote mental health, a satisfactory understanding of the mechanism underlying this phenomenon has not yet been achieved. A new mechanism is proposed that is based on established concepts in cognitive psychology and the neurosciences as well as recent empirical work on the functional neuroanatomy of higher mental processes. Building on the fundamental principle that processing in the brain is competitive and the fact that the brain has finite metabolic resources, the transient hypofrontality hypothesis suggests that during exercise the extensive neural activation required to run motor patterns, assimilate sensory inputs, and coordinate autonomic regulation results in a concomitant transient decrease of neural activity in brain structures, such as the prefrontal cortex, that are not pertinent to performing the exercise. An exercise-induced state of frontal hypofunction can provide a coherent account of the influences of exercise on emotion and cognition. The new hypothesis is proposed primarily on the strength of its heuristic value, as it suggests several new avenues of research.

Heat stress, plasma concentrations of adrenaline, noradrenaline, 5-hydroxytryptamine and cortisol, mood state and cognitive performance

The primary aims of this paper were to examine the effect of heat stress on working memory, choice reaction time and mood state, and to investigate the relationship between heat induced changes in plasma concentrations of selected neurotransmitters and hormones, and cognition. Heat stress resulted in a deterioration of performance on a central executive task (random movement generation) but not on verbal and spatial recall, and choice reaction time tasks. Perceptions of vigour decreased and fatigue increased following exposure to heat stress. Plasma concentrations of cortisol and 5-hydroxytryptamine significantly increased following exposure to heat. Regression analyses showed that percent body mass loss and change from baseline (Delta) concentrations of cortisol, post-exposure to heat, were significant predictors of Delta random movement generation and Delta fatigue. A secondary purpose was to examine the effect of recovery on cognition and mood. Following recovery, the performance of the central executive task was poorer than pre-treatment. Mood states, catecholamines and 5-hydroxytryptamine concentrations returned to pre-treatment values, but cortisol fell to a level significantly lower. Regression correlations showed that Delta adrenaline and Delta scores, post-recovery, on the central executive task were significantly correlated. Delta noradrenaline correlated significantly with Delta fatigue. It was concluded that heat stress results in deterioration in the performance of central executive tasks and perceptions of mood state, and that this can be predicted by changes in body mass loss and plasma concentrations of the hormones cortisol and adrenaline.

Effect of creatine supplementation and sleep deprivation, with mild exercise, on cognitive and psychomotor performance, mood state, and plasma concentrations of catecholamines and cortisol

RATIONALE

Sleep deprivation has a negative effect on cognitive and psychomotor performance and mood state, partially due to decreases in creatine levels in the brain. Therefore, creatine supplementation should lessen the negative effects of sleep deprivation.

OBJECTIVES

The objective of this study was to examine the effect of creatine supplementation and sleep deprivation, with mild exercise, on cognitive and psychomotor performance, mood state, and plasma concentrations of catecholamines and cortisol.

METHOD

Subjects were divided into a creatine group (n=10) and a placebo group (n=9). They took 5 g of creatine monohydrate or a placebo, dependent on their group, four times a time a day for 7 days, immediately prior to the experiment. The study was double blind. Subjects undertook tests of random movement generation (RMG), verbal and spatial recall, choice reaction time, static balance and mood state pre-test (0 h), after 6, 12 and 24 h of sleep deprivation, with intermittent exercise. They were tested for plasma concentrations of catecholamines and cortisol at 0 and 24 h.

RESULTS

At 24 h, the creatine group demonstrated significantly less change in performance from 0 h (delta) in RMG, choice reaction time, balance and mood state. There were no significant differences between groups in plasma concentrations of catecholamines and cortisol. Norepinephrine and dopamine concentrations were significantly higher at 24 h than 0 h, but cortisol were lower.

CONCLUSIONS

Following 24-h sleep deprivation, creatine supplementation had a positive effect on mood state and tasks that place a heavy stress on the prefrontal cortex.

Endocannabinoids and exercise

Exercise induces changes in mental status, particularly analgesia, sedation, anxiolysis, and a sense of wellbeing. The mechanisms underlying these changes remain unknown. Recent findings show that exercise increases serum concentrations of endocannabinoids, suggesting a possible explanation for a number of these changes. This article provides an overview of this emerging field.

Neurocognitive mechanisms underlying the experience of flow

Recent theoretical and empirical work in cognitive science and neuroscience is brought into contact with the concept of the flow experience. After a brief exposition of brain function, the explicit-implicit distinction is applied to the effortless information processing that is so characteristic of the flow state. The explicit system is associated with the higher cognitive functions of the frontal lobe and medial temporal lobe structures and has evolved to increase cognitive flexibility. In contrast, the implicit system is associated with the skill-based knowledge supported primarily by the basal ganglia and has the advantage of being more efficient. From the analysis of this flexibility/efficiency trade-off emerges a thesis that identifies the flow state as a period during which a highly practiced skill that is represented in the implicit system's knowledge base is implemented without interference from the explicit system. It is proposed that a necessary prerequisite to the experience of flow is a state of transient hypofrontality that enables the temporary suppression of the analytical and meta-conscious capacities of the explicit system. Examining sensory-motor integration skills that seem to typify flow such as athletic performance, writing, and free-jazz improvisation, the new framework clarifies how this concept relates to creativity and opens new avenues of research.

Functional neuroanatomy of altered states of consciousness: the transient hypofrontality hypothesis

It is the central hypothesis of this paper that the mental states commonly referred to as altered states of consciousness are principally due to transient prefrontal cortex deregulation. Supportive evidence from psychological and neuroscientific studies of dreaming, endurance running, meditation, daydreaming, hypnosis, and various drug-induced states is presented and integrated. It is proposed that transient hypofrontality is the unifying feature of all altered states and that the phenomenological uniqueness of each state is the result of the differential viability of various frontal circuits. Using an evolutionary approach, consciousness is conceptualized as hierarchically ordered cognitive function. Higher-order structures perform increasingly integrative functions and thus contribute more sophisticated content. Although this implies a holistic approach to consciousness, such a functional hierarchy localizes the most sophisticated layers of consciousness in the zenithal higher-order structure: the prefrontal cortex. The hallmark of altered states of consciousness is the subtle modification of behavioral and cognitive functions that are typically ascribed to the prefrontal cortex. The theoretical framework presented yields a number of testable hypotheses.