Michel Audiffren

The reticular-activating hypofrontality (RAH) model of acute exercise.

We present here a comprehensive, neurocognitive model to account for the psychological consequences of acute exercise. There is a substantial amount of disparate research and the proposed mechanistic explanation meaningfully integrates this body of brain and behavioral data into a single, unified model. The models central feature is a cascading, two-step process. First, exercise engages arousal mechanisms in the reticular-activating system. This activation process, which involves a number of neurotransmitter systems, has several interrelated effects on cognition and emotion but, in general, has evolved to facilitate implicit information processing. Second, exercise disengages the higher-order functions of the prefrontal cortex. This deactivation process, which is caused in part by resource limitations, also has several interrelated effects but, in general, has evolved to keep the inefficient explicit system and unhelpful emotional processes from compromising the implicit systems functioning when optimal motor execution is needed most. In this article, we review evidence in support of this reticular-activating hypofrontality (RAH) model of acute exercise and place it into a larger evolutionary context.

Facilitating effects of exercise on information processing

The aim of this study was to examine the facilitating effects of moderate physical exercise on the reaction process to gain a better understanding of the interaction between physiological and cognitive processes. Sixteen participants with specific expertise in decision-making sports performed a double task consisting of choice reaction time while cycling. Signal quality, stimulus–response compatibility and time uncertainty were manipulated. Participants were tested at rest and while cycling at 20% and at 50% of their maximal aerobic power. A mood assessment questionnaire and a critical flicker fusion test were administered before and after the choice reaction time task. The results showed that moderate-intensity exercise (50% maximal aerobic power) improves cognitive performance and that low-intensity exercise (20% maximal aerobic power) enables participants to compensate the negative dual-task effect.

Information processing during physical exercise: a chronometric and electromyographic study

Choice reaction time (RT) is shorter when participants perform a choice task at the same time as a sub-maximal exercise than when they are at rest. The purpose of the present study was to determine whether such an exercise affects response execution or whether it alters processes located upstream from the neuro-muscular level. To this end, the electromyographic (EMG) activity of the response agonists was analysed in a between-hand choice RT task performed either concurrently with a pedalling task or at rest. Visual stimulus intensity was also manipulated so as to determine whether exercise further affects early sensory processes. Results shows that exercise affected the time interval elapsing from the onset of the contraction of the response agonists to the mechanical response, thereby indicating that this variable modifies the peripheral motor processes involved in response execution. EMG signal analyses further revealed that the cortico-spinal command is more efficient during exercise than at rest. In addition, exercise was shown to interact with visual stimulus intensity on the time between stimulus and voluntary EMG onset and to increase the critical flicker fusion frequency threshold, thereby indicating that exercise modifies the peripheral sensory processes involved in early sensory operations. The decomposition of RT, with respect to the EMG activity of response agonists, sheds light on the processes affected by exercise and suggests that exercise affects both sensory processes and late motor processes.

Processing speed and executive functions in cognitive aging: How to disentangle their mutual relationship?

The processing-speedtheory and the prefrontal-executivetheory are competing theories of cognitive aging. Here we used a theoretically and methodologically-driven framework to investigate the relationships among measures classically used to assess these two theoretical constructs. Twenty-eight young adults (18-32 years) and 39 healthy older adults (65-80 years) performed a battery of nine neuropsychological and experimental tasks assessing three executive function (EF) components: Inhibition, Updating, and Shifting. Rate of information processing was evaluated via three different experimental and psychometric tests. Partial correlations analyses suggested that 2-Choice Reaction Time (CRT) performance is a more pure measure of processing speed than Digit Symbol Substitution Test (DSST) performance in the elderly. Hierarchical regression analyses showed that, although measures of processing speed and EF components share mutual variance, each measure was independently affected by chronological age. The unique adverse effect of age was more important for processing speed than for EF. The processing-speed theory and the prefrontal-executive theory of cognitive aging were shown not to be mutually exclusive but share mutual variance. This implies the need to control for their mutual relationship before examining their unique potential role in the explanation of age-related cognitive declines. Caution has still to be taken concerning the tasks used to evaluate these theoretical constructs.

Physical exercise facilitates motor processes in simple reaction time performance: An electromyographic analysis

The aim of the current study was to assess the effects of physical exercise on simple reaction time performance. Participants performed a simple reaction time task twice, one time during physical exercise and another time without exercise. Electromyographic signals were recorded from the thumb of the responding hand to fraction reaction time in pre-motor and motor time. The results showed that exercise shortened motor time but failed to affect pre-motor time. This pattern of findings is consistent with previous studies examining the effects of physical exercise on choice reaction time.

Effects of a Prolonged Run on Simple Reaction Time of Well Trained Runners

The aim of the present study was to examine the effect of increased arousal induced by a prolonged exercise at ventilatory threshold on a simple reaction time performance performed during a running task. 11 well trained triathletes completed two testing sessions within a 2-wk. period. The first session was a protocol of VO2 max determination conducted on a treadmill. This protocol was used to assess the velocity associated with ventilatory threshold (vVvt). The second session was a 90-min. running test performed at vVvt. This last session was composed of five submaximal treadmill runs (10-min. long, 0% grade) separated by four overground runs (10-min.). Before, during each treadmill run, and after exercise, subjects performed three blocks of 20 simple reaction time. Furthermore, at the end of each overground run, perceived exertion (RPE) was recorded. Analysis showed a significant impairment in Simple RT performance during the first treadmill run only. After this first run a significant effect of exercise duration on Simple RT was observed. After 40-min. of exercise a significant improvement in reaction time during exercise was recorded. Furthermore, when Simple RT was recorded at rest, there was no difference pre-exercise and postexercise. These results suggest that a simple cognitive performance could be improved during exercise, despite the negative effect of the dual task. This improvement in reaction time could be explained mainly by an increase in arousal induced by a prolonged exercise.

A distributional analysis of the effect of physical exercise on a choice reaction time task

Abstract The aim of this study was to examine the facilitating effects of physical exercise on the reaction process. Eleven participants with specific expertise in decision-making sports performed a choice reaction time task during moderate sub-maximal exercise (90% of their ventilatory threshold power). Participants were tested at rest and while cycling. During exercise, the participants were faster, without being more variable. We suggest that the effect of exercise on cognitive performance was due to a major generalized improvement of the whole distribution of response time and, although the benefit effect was small, it was consistent throughout the entire range of reaction times.

The interactive effect of achievement motivation and task difficulty on mental effort

The interactive effect of achievement motivation and task difficulty on invested mental effort, postulated by Humphreys and Revelle [Humphreys, M.S., Revelle, W., 1984. Personality, motivation, and performance: a theory of the relationship between individual differences and information processing. Psychol. Rev. 91, 153-184], was examined using behavioral, subjective, and effort-related physiological measures. Eighteen approach-driven participants and 18 avoidance-driven participants were selected based on their motive to achieve success scores and their motive to avoid failure scores. A 2x3 factorial design was used, with three levels of task difficulty. As expected, approach-driven participants performed better and had a stronger decrease of midfrequency band of heart rate variability than avoidance-driven participants, especially during the difficult task. These results support the interactive effect of achievement motivation and task difficulty on invested mental effort.

Reliability of heart rate measures used to assess post-exercise parasympathetic reactivation

Postexercise HRR (heart rate recovery) and HRV (heart rate variability) are commonly used to asses non‐invasive cardiac autonomic regulation and more particularly reactivation parasympathetic function. Unfortunately, the reliability of postexercise HRR and HRV remains poorly quantified and is still lacking. The aim of this study was to examine absolute and relative reliability of HRR and HRV indices used to assess postexercise cardiac parasympathetic reactivation.

The effects of achievement motivation, task difficulty, and goal difficulty on physiological, behavioral, and subjective effort

The purpose of the study was to present experimental arguments evaluating the Humphreys and Revelles model of effort. Two important factors were tested: achievement motivation and difficulty. Heart rate, heart rate variability, blood pressure, facial electromyographic reactivity, and reaction time were measured as an index of effort expenditure. A 2x2x2 factorial design was used with two levels of resultant achievement motivation, two levels of task difficulty, and two levels of goal difficulty. As expected, the 16 participants high in resultant achievement motivation showed a better performance and had a larger decrease of the midfrequency band than the 16 participants low in resultant achievement motivation, especially during the difficult task. Results lend some support for the impact of resultant achievement motivation, task difficulty, and goal difficulty on effort mobilization.