Individual differences in the ability to identify, select and use appropriate frames of reference for perceptuo-motor control.

The causes of the interindividual differences (IDs) in how we perceive and control spatial orientation are poorly understood. Here, we propose that IDs partly reflect preferred modes of spatial referencing and that these preferences or "styles" are maintained from the level of spatial perception to that of motor control. Two groups of experimental subjects, one with high visual field dependency (FD) and one with marked visual field independency (FI) were identified by the Rod and Frame Test, which identifies relative dependency on a visual frame of reference (VFoR).

Are there specific conditions for which expertise in gymnastics could have an effect on postural control and performance?

The first aim of this study was to analyse the effect of elite training, linked to expertise, in gymnastics on postural performance and control. For this purpose, body sway of expert gymnasts was compared to other sportsmen, non-experts and non-gymnasts, in two different postures: bipedal (easy and unspecific to gymnasts) and unipedal (difficult and fairly specific). The second aim was to compare the groups in the same tasks but in a visual condition for which they were not trained, i.

Perceived versus actual head-on-trunk orientation during arm movement control.

Static roll head tilt induces bias in the trajectory of upper limb voluntary movements. The aim of the experiment was to investigate whether this bias is dependant on the perception of body configuration rather than on its actual configuration. We used the 'return' phenomenon as a method to produce dissociation between perceived and actual head tilt.

Effects of the removal of vision on body sway during different postures in elite gymnasts.

The aim of this study was to analyse the effects of the removal of vision on postural performance and postural control in function of the difficulty and specificity of the posture. Twelve elite gymnasts were instructed to be as stable as possible with eyes open and eyes closed in three postures: bipedal, unipedal, and handstand ranked from the less difficult and less specific to the more difficult and more specific. The ratios eyes closed on eyes open, computed on CP surface and CP mean velocity, which respectively represents postural performance and postural control, were similar in the bipedal and handstand postures.

Influence of exercise duration and hydration status on cognitive function during prolonged cycling exercise.

The purpose of the present study was to examine the influence of submaximal aerobic exercise duration on simple and complex cognitive performance. Eight well-trained male subjects agreed to participate in this study (trial group). A control group of eight regularly trained male subjects was included for comparative purposes.

Apnea-induced changes in time estimation and its relation to bradycardia.

Introduction: Both exercise and hypoxia affect human ability to estimate time, an alteration thought to be induced by changes in subjects' level of arousal. Apnea induces cardiovascular changes and a decrease in oxygen uptake that indicate changes in physiological arousal. We tested time estimation (TE) during brief periods of voluntary apnea.

Effects of ventilation on body sway during human standing.

Body sway was studied in standing with eyes closed during quiet breathing and apnoea. The hypothesis was that absence of ventilation improved balance. Performance and control of balance were assessed by centre of gravity and centre of pressure motions respectively.

Is there a transfer of postural ability from specific to unspecific postures in elite gymnasts?

The purpose of this study was to investigate the transfer of postural ability by comparing the level of performance and postural control of elite gymnasts in postures specifically trained or not. Fifteen elite gymnasts were asked to stand as still as possible with eyes opened in three conditions: bipedal, unipedal and handstand. Surface and mean velocity of the centre of pressure motions were used to quantify respectively performance and postural control.

Differential approach to strategies of segmental stabilisation in postural control.

The present paper attempts to clarify the between-subjects variability exhibited in both segmental stabilisation strategies and their subordinated or associated sensory contribution. Previous data have emphasised close relationships between the interindividual variability in both the visual control of posture and the spatial visual perception. In this study, we focused on the possible relationships that might link perceptual visual field dependence-independence and the visual contribution to segmental stabilisation strategies.

Influence of physical exercise on perceptual response in aerobically trained subjects.

A significant effect of fatigue induced byphysical exercise leading to exhaustion was observed for 6 male triathletes using some specific analysis of the critical flicker fusion test.

Visual contribution to self-induced body sway frequencies and visual perception of male professional dancers.

We studied the degree of dependence on vision, for postural control and for perception, among male adult dancers and untrained subjects. First, body sways were analyzed on a free seesaw platform. Fast Fourier transform processing allowed spectral frequency analysis of the platform sways recorded by an accelerometer.

Effect of physical training on head-hip co-ordinated movements during unperturbed stance.

A cross-correlation analysis between head and hip lateral accelerations has been used to analyse the effects of sport training (in experts in judo or classical dance as compared to controls) on postural strategies during unperturbed stance. Subjects were standing in the sharpened Romberg position on either a hard or foam rubber support. The main results were: (1) several non-visual and ankle-like strategies (head-hip movements in the same sense) were used by both groups on both supports; (2) two types of lateral hip strategies (head-hip movements in opposite sense) were seen in controls on soft support only, and were mainly modulated by vision.

Selection of spatial frame of reference and postural control variability.

The present paper addresses the question of the possible links between perceptive visual field dependence-independence and the visual contribution to postural control. In our differential approach, visual field dependent (FD) and independent (FI) subjects were selected on the basis of their score in the Rod and Frame Test (subjective vertical). The hypothesis that we have tested is that the FD subjects use mainly visual cues for estimating not only their subjective vertical but also their body orientation and stability.

Cross-correlation analysis of the lateral hip strategy in unperturbed stance.

Subjects standing heel-to-toe on either hard ground or soft support were instructed to stand upright keeping optimal balance. Lateral accelerometric measurements at head, hip and ankle levels were subjected to conjugate cross-correlations analysis in order to determine the co-ordinated movements or strategies. The results strongly suggest that there exists a hip lateral strategy which is very similar to the hip strategy previously described in fore-aft body oscillations.

Differential sensitivity to static visual cues in the control of postural equilibrium in man.

Decreasing the visual sampling rate by reducing the stroboscopic frequency affected the postural performance of human subjects. At low strobe frequencies of up to 2 flashes/sec., at which only static visual cues were available, no decrease in subjects' mean postural sway was previously observed as compared to their equilibrium behavior without vision.

Use of an ultrasonic echolocation prosthesis by early visually deprived cats.

The aim of this study was to design an animal model of sensory substitution in the case of blindness. Six kittens were binocularly enucleated; as adults, they were fitted with an ultrasonic echolocation prosthesis. This device provided the animals with auditory signals that coded distance and direction of obstacles.

[Non-linear development of the frequency of swimming movements during ontogeny in rats].

The choice of swimming as locomotor behaviour was justified by the fact that it could be elicited from birth to adult age. We have recorded electromyographic activities during swimming movements, on flexor muscles in front legs and hind legs (Spinodeltoidus and Gluteus superficialis). The mean frequency of activity of each limb during swimming, for animals aged from 0 to 20 or 30 days was then computed.

Variability as a characteristic of immature motor systems: an electromyographic study of swimming in the newborn rat.

Swimming behaviour was studied in neonate rats by carrying out electromyographic recordings. The study showed that the early swimming pattern was characterized by highly instable temporal parameters. A decrease was found to occur with age in the variability of the instantaneous period in each leg and in that of the antiphase pattern.

Early sensory determinants of locomotor speed in adult cats: II. Effects of strobe rearing on vestibular functions.

Cats raised under stroboscopic illumination are known to exhibit oculomotor and visuomotor deficits, but little is known about their locomotor abilities. Four strobe-reared cats with intact labyrinths were tested in a locomotor test involving various walking surfaces and various illumination conditions. Apart from their general slowness under all the experimental conditions, these strobe cats showed no special deficit on narrow rails, which indicates that their dynamic balancing abilities were normal.

Two types of motor rhythm induced by NMDA and amines in an in vitro spinal cord preparation of neonatal rat.

Rhythmic motor activities were studied in two rat spinal cord preparations; in the first one, the spinal cord was completely isolated and the ventral roots activity was recorded; in the other, spinal cord and hindlimbs were kept in order to record muscle activities. Motor patterns were therefore recorded in ventral roots and/or hindlimb muscles. Two kinds of specific patterns were elicited by neurochemicals.

Experimental myopia in cats reared in stroboscopic illumination.

Spectacle refraction of eyes of strobe-reared animals was compared to that of normal cats. Strobe reared cats were found to be significantly more myopic than normal cats.

Response properties of area 17 neurons in cats reared in stroboscopic illumination.

The response properties of 196 area 17 cells were studied qualitatively in seven cats reared from birth in a stroboscopically illuminated environment (frequency, 2/s; duration, 200 microseconds). Quantitative testing with the multihistogram technique was carried out in 115 cells. As control population, 453 neurons recorded in area 17 of the normal adult cat and tested qualitatively (of which 301 neurons were tested quantitatively) were available.