Biomedical subjects

M Audiffren

Publications and source records attributed to M Audiffren.

9 recordsLinked to original sources

PubMed2006

Perceptual factors contribute to akinesia in Parkinson's disease.

Parkinson's disease (PD) patients have longer reaction time (RT) than age-matched control subjects. During the last decades, conflicting results have been reported regarding the source of this deficit. Here, we addressed the possibility that experimental inconsistencies originated in the composite nature of RT responses. To investigate this idea, we examined the effect of PD on different processes that compose RT responses. Three variables were manipulated: the signal quality, the stimulus-response compatibility and the foreperiod duration. These variables have been shown to affect, respectively, the ability to extract the relevant features of the stimulus (perceptual stage), the intentional selection of the motor response (cognitive stage) and the implementation of the muscle command (motor stage). Sixteen PD patients were tested on and off-medication and compared with an age and gender-matched control group. Results indicated that degrading the legibility of the response stimulus affected the latency of simple key-press movements more dramatically in the off-medication PD group than in the control population. The stimulus-response compatibility and the foreperiod duration had similar effects in the two groups. Interestingly, the response slowing associated with the degradation of the stimulus was the same whether the patients were on or off dopaminergic medication. This suggests that the high-level perceptual deficits observed in the present study do not have a dopaminergic origin.

Adult↗

PubMed2001

Single and choice reaction time during prolonged exercise in trained subjects: influence of carbohydrate availability.

The aim of the present study was to examine the effects of prolonged exercise at the ventilatory threshold and carbohydrate ingestion on single (SRT) and choice (CRT) reaction time. Eight well-trained triathletes completed three testing sessions within a 3-week period. Maximal oxygen uptake was determined in the first test, whereas the second and the third sessions were composed of a 100-min run (treadmill 15 min, overground 70 min, treadmill 15 min) performed at the velocity associated with the ventilatory threshold. During these submaximal tests, the subjects ingested (in random order) 8 ml x kg(-1) body weight of either a placebo (Pl) or 5.5% carbohydrate (CHO) solution prior to the first submaximal run and 2 ml x kg(-1) body weight every 15 min after that. The cognitive tasks were performed before and after exercise for CRT, and before, during each submaximal run and after exercise for SRT. Furthermore, at the end of each submaximal test subjects were asked to report their rating of perceived exertion (RPE). Results showed a significant positive effect of CHO ingestion on RPE and CRT performance at the end of exercise, while no effect of exercise duration was found in the Pl condition. After a 100-min run, during the CHO condition, CRT mean (SD) group values decreased from 688.5 (51) ms to 654 (63) ms, while during the Pl condition, RPE mean group values increased from 11 (2) to 16 (1.02) and CRT mean values remained stable [688 (104) ms vs 676 (73.4) ms, P > 0.05]. No similar effect was observed for SRT. These results suggest that CHO-electrolyte ingestion during a 100-min run results in an improvement in the complex cognitive performance measured at the end of that run.

Adult↗

PubMed2001

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 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.

Adult↗

PubMed2001

[Change in effects of motor preparation due to priming as a function of the amount of practice].

The goal of the present experiment is to assess the effects of motor preparation on reaction time (RT) as a function of practice. We used a priming procedure to induce different levels of motor preparation. In reaction to a visual signal, the 16 participants had to respond with a flexion or an extension of the right or left wrist. Each participant performed 6120 successful trials divided into 34 experimental series. The first analysis of RT as a function of the type of cue (valid, neutral, or invalid) suggested that the time needed (a) to inhibit the prepared response and (b) to program the required one, remains stable throughout practice. A second analysis on the amount of information to be processed according to type of cue (0.42, 2.00, and 3.58 bits) indicated that central processing speed did not vary with practice. Indeed, only RT for the 0 bit condition decreased during the first 720 trials, suggesting that only the peripheral processes were influenced in early learning.

Adult↗

PubMed2000

Local muscular fatigue and attentional processes in a fencing task.

Study of the effects of brief exercise on mental processes by Tomporowski and Ellis (1986) has shown that moderate muscular tension improves cognitive performance while low or high tension does not. Improvements in performance induced by exercise are commonly associated with increase in arousal, while impairments are generally attributed to the effects of muscular or central fatigue. To test two hypotheses, that (1) submaximal muscular exercise would decrease premotor time and increase would increase the attentional and preparatory effects observed in premotor time 9 men, aged 20 to 30 years, performed an isometric test at 50% of their maximum voluntary contraction between blocks of a 3-choice reaction-time fencing task. Analysis showed (1) physical exercise did not improve postexercise premotor time, (2) muscular fatigue induced by isometric contractions did not increase motor time, (3) there was no effect of exercise on attentional and preparatory processes involved in the postexercise choice-RT task. The invalidation of hypotheses was mainly explained by disparity in directional effects across subjects and by use of an exercise that was not really fatiguing.

Adult↗

PubMed2000

Study of anticipatory postural adjustments in an air pistol-shooting task.

A segmental teleokinetic movement performed from an upright standing position is usually preceded by a sequence of postural movements having the goal of counteracting the imbalance which will be caused by the forthcoming movement. This study had two aims, (1) to verify whether the postural component was programmed in the same way as that of the teleokinetic component and (2) to verify whether the postural component was specific to the direction and speed of the movement. 12 participants performed a pistol-shooting task involving a rapid arm-raising movement. Three directions, two time deadlines, and three types of cue were manipulated. This study showed that the postural component was sensitive to the cue effects, the characteristics of anticipatory postural adjustments were specific to the direction of the movement, and the characteristics of the postural muscle EMG burst were the same whether the participants programmed or deprogrammed and reprogrammed their movements for a given direction. The speed parameter did not seem to have any significant influence on the characteristics of the anticipatory postural adjustments.

Adolescent↗

PubMed1998

Age-related differences in the preparatory processes of motor programming.

This article investigates the mechanisms underlying the age-related differences in information processing in the production of motor responses, especially the development of feedforward mechanisms. No age-related differences have emerged from developmental studies aiming at analyzing motor programming. Nevertheless, age effects have seldom been studied in function of motor preparation. The aim of the present experiment was (1) to study age differences in motor preparation, and (2) to validate the early maturation of movement parameters specification. Two conditions were used (1) no advanced information on the movement to be made was given to the subject (neutral prime), and (2) advanced information on which direction should be followed was provided to the subject, allowing him to prepare a response based on a prime (primed condition). Four age groups were studied 6, 8, 10 and 22 years. Our results showed mainly an early maturation of the programming processes. More specifically, (1) beyond 6 years of age, children are capable of using the information provided by the prime to prepare their movement in advance, (2) costs and benefits of pre-programming do not vary significantly with age, (3) deprogramming-reprogramming of effector and direction is quite similar across the four age groups.

Adult↗

PubMed1997

Age differences in using precued information to preprogram interception of a ball.

The present experiment examined the development of programming interception of a ball's movement across three groups of children ages 6, 8, and 10 years, who were compared with adults. In an interception task we manipulated the subjects' preparation by using Rosenbaum's 1980 precuing procedure. Two levels of precued information were used concerning the effector specified (right or left arm) and the direction of the arm projection (outside or inside). We focused particularly on RT and response errors. Analysis indicated RT decreased across the age groups and errors decreased mainly in the nonprecued condition. A critical period in improvement might be at age 8 as children use precue information to program their movements as efficiently as adults. The duration of effector programming was similar for children and adults but was more precise for the older subjects. For children as well as for adults, the specification of direction occurs after movement initiation and not before.

Adult↗

PubMed1997

Influence of physical exercise on simple reaction time: effect of physical fitness.

The influence of physical fitness and energy expenditure on a simple reaction time task performed during exercise was investigated. Two groups of 10 subjects were used, one was composed of trained middle-distance runners and one of students who had no regular physical training. The subjects performed a simple reaction time task while pedalling on a cycloergometer at different relative power output corresponding to 20, 40, 60, and 80% of their own maximal aerobic power and immediately after exercise. During exercise, the results showed a decrease in cognitive performance for both groups whereas no significant effect was found after exercise. A significant effect of physical fitness on simple reaction time was noted during exercise. The data are interpreted in terms of optimization of performance focusing particularly on the relations between energy cost of the physical task and attentional demand.

Adult↗