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Motor control, including locomotion, strongly depends on the gravitational field. Recent developments such as lower-body positive pressure treadmills (LBPPT) have enabled studies on Earth about the effects of reduced body weight (BW) on walking and running, up to 60% BW. The present experiment was set up to further investigate adaptations to a more naturalistic simulated hypogravity, mimicking a Martian environment with additional visual information during running sessions on LBPPT. Twenty-nine participants performed three sessions of four successive five-min runs at preferred speed, alternating Earth- or simulated Mars-like gravity (100% vs. 38% BW). They were displayed visual scenes using a virtual reality headset to assess the effects of coherent visual flow while running. Running performance was characterized by normal ground reaction force and pelvic accelerations. The perceived upright and vection (visually-induced self-motion sensation)in dynamic visual environments were also investigated at the end of the different sessions. We found that BW reduction induced biomechanical adaptations independently of the visual context. Active peak force and stance time decreased, while flight time increased. Strong inter-individual differences in braking and push-off times appeared at 38% BW, which were not systematically observed in our previous studies at 80% and 60% BW. Additionally, the importance given to dynamic visual cues in the perceived upright diminished at 38% BW, suggesting an increased reliance on the egocentric body axis as a reference for verticality when the visual context is fully coherent with the previous locomotor activity. Also, while vection was found to decrease in case of a coherent visuomotor coupling at 100% BW (i.e., post-exposure influence), it remained unaffected by the visual context at 38% BW. Overall, our findings suggested that locomotor and perceptual adaptations were not similarly impacted, depending on the -simulated- gravity condition and visual context.

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Introduction: Originally developed for astronauts, lower body positive pressure treadmills (LBPPTs) are increasingly being used in sports and clinical settings because they allow for unweighted running. However, the neuromuscular adjustments to unweighted running remain understudied. They would be limited for certain lower limb muscles and interindividually variable. This study investigated whether this might be related to familiarization and/or trait anxiety. Methods: Forty healthy male runners were divided into two equal groups with contrasting levels of trait anxiety (high, ANX+, n = 20 vs. low, ANX-, n = 20). They completed two 9-min runs on a LBPPT. Each included three consecutive 3-min conditions performed at 100%, 60% (unweighted running), and 100% body weight. Normal ground reaction force and electromyographic activity of 11 ipsilateral lower limb muscles were analyzed for the last 30 s of each condition in both runs. Results: Unweighted running showed muscle- and stretch-shortening cycle phase-dependent neuromuscular adjustments that were repeatable across both runs. Importantly, hamstring (BF, biceps femoris; STSM, semitendinosus/semimembranosus) muscle activity increased during the braking (BF: +44 ± 18%, p < 0.001) and push-off (BF: +49 ± 12% and STSM: +123 ± 14%, p < 0.001 for both) phases, and even more so for ANX+ than for ANX-. During the braking phase, only ANX+ showed significant increases in BF (+41 ± 15%, p < 0.001) and STSM (+53 ± 27%, p < 0.001) activities. During the push-off phase, ANX+ showed a more than twofold increase in STSM activity compared to ANX- (+119 ± 10% vs. +48 ± 27, p < 0.001 for both). Conclusion: The increase in hamstring activity during the braking and push-off phases may have accelerated the subsequent swing of the free-leg, likely counteracting the unweighting-induced slowing of stride frequency. This was even more pronounced in ANX+ than in ANX-, in an increased attempt not to deviate from their preferred running pattern. These results highlight the importance of individualizing LBPPT training and rehabilitation protocols, with particular attention to individuals with weak or injured hamstrings.

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Evidence from extreme environments suggests that there are relationships between difficulties of adaptation and psychological factors such as personality. In the framework of microgravity research on humans, the aim of this exploratory study was to investigate inter-individual differences of parabonauts on the basis of quality of adaptation to the physical demands of parabolic flights. The personality characteristics of two groups of parabonauts with a different quality of adaptation (an Adaptive group, N = 7, and a Maladaptive group, N = 15) were assessed using the Sensation Seeking Scale, Brief COPE, and MSSQ-Short. Compared to the Maladaptive group, the individuals of the Adaptive group scored higher on Boredom Susceptibility (i.e., a subscale of the Sensation Seeking Scale), lower on scales of susceptibility to motion sickness (MSSQ-Short) and tended to score lower on Instrumental Support Seeking (i.e., a subscale of the Brief COPE). These results suggest that individuals of the Adaptive group are more intolerant to monotony, present an aversion to repetitive and routine activities, are less susceptible to motion sickness and less dependent on problem-focused strategies. These characteristics may have contributed to developing a certain degree of flexibility in these subjects when faced with the parabolic flight situation and thus, may have favored them. The identification of differences of personality characteristics between individuals who have expressed difficulties of adaptation from those who have adapted successfully could help to prevent the risk of maladaptation and improve the well-being of (future) commercial or occupational aerospace passengers. More generally, these results could be extended to extreme environments and professional and/or sports domains likely to involve risk taking and unusual situations.

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BACKGROUND: Working memory is the most impaired cognitive domain in the acute phase of stroke. In a context where anxiety is highly prevalent, close attention must be paid to anxiety which could mimic mild to moderate working memory impairments. This is the first study to assess the contribution of state anxiety (the currently experienced level of anxiety) to the working memory (verbal, visuospatial) in patients with first-ever acute stroke without severe cognitive impairment. METHODS: 28 patients with first-ever acute stroke and 41 matched control subjects were exposed to a neutral condition and an anxiogenic condition in which verbal (VWM) and visuospatial working memory (VSWM) performance and state anxiety were assessed. State anxiety was assessed before the beginning of the experiment (baseline), after the neutral condition and after the anxiogenic condition. RESULTS: The mean state anxiety score was higher in patients than in controls in the neutral (z = 1.9, p<0.05) and anxiogenic (z = 2, p<0.05) conditions despite a similar level at baseline. Multiple regression analyses with a dummy variable 'group' (patients vs controls) showed that increased state anxiety in patients contributed significantly more to both reduced VWM (ß = -0.93, p<0.05) and VSWM (ß = -1, p<0.05) performance between the neutral and anxiogenic conditions compared to controls. CONCLUSIONS: In a stressful context, the contribution of state anxiety to reduced working memory performance is more pronounced in patients with acute stroke than in controls. These results are of particular relevance for clinicians assessing patients in the acute phase of stroke in which anxiety is highly prevalent.

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BACKGROUND: Studies have shown that members of expeditions in extreme environments differed on the basis of personality factors (e.g., they were highly competitive, higher on Extraversion and Conscientiousness) compared to the control population. In order to identify individuals who are likely to participate in extreme environments, the aim of the present study using parabolic flights was to compare the personality traits of voluntary participants (VP) in a weightlessness experiment with those of the general population (GP) (French norms). METHODS: The personalities of 57 voluntary participants in a parabolic flights experiment were assessed using NEO-PI-R and Trait-Anxiety. RESULTS: Our results show significant differences with the general population: (1) in Trait-Anxiety (GP = 42.25 +/- 11.44 vs. VP = 34.56 +/- 6.24) and in 3 out of 5 personality domains (Neuroticism GP = 90.04 +/- 22.68 vs. VP = 78.70 +/- 17.44, +/- 18.87 vs. VP = 123.81 +/- 15.41, and Conscientiousness GP = 109.23 +/- 22.30 vs. VP = 124.47 + 19.03); and (2) in 14 out of 30 NEO-PI-R facets. DISCUSSION: These findings indicate a specific personality profile for voluntary participants in parabolic flights and confirm that participants attracted to extreme environments differ compared to the normative population.

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OBJECTIVE: In view of the negative impact of anxiety on working memory, we induced anxiety in 26 patients with acute stroke and 33 healthy controls, and studied how the anxiety affected their emotional reactivity and how the reactivity affected their verbal and visuospatial working memory. We compared the overall findings with those in 1 of our patients (C.B.) who had presented with an abnormally high level of state anxiety. METHODS: We gave verbal and visuospatial 1-back tasks under both neutral and anxiogenic conditions, and we compared participants' working memory scores, self-reported levels of state anxiety, and electrodermal activity. RESULTS: When comparing performance in the neutral condition, the control and patient groups exhibited disrupted verbal working memory, which was associated with greater electrodermal activity and higher state anxiety during the anxiogenic condition. Although patient C.B. also had heightened electrodermal activity during the anxiogenic condition, she experienced a significant reduction in her state anxiety. Her verbal working memory was better during the anxiogenic than the neutral condition. CONCLUSIONS: Because of the phonological (subvocal speech) nature of verbal working memory, a higher level of anxious apprehension could explain the increase in state anxiety and the corresponding disruption of verbal working memory in our patient and control groups during the anxiogenic condition. C.B.'s lower state anxiety and selective improvement in verbal working memory during the anxiogenic condition suggest that she felt less anxious apprehension.

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It has proved difficult to demonstrate the differences in physiological response in individuals with contrasting trait anxiety levels. The purpose of this study was to examine tonic autonomic activity and muscle tension in male subjects with different levels of trait anxiety during and especially after a stressful situation. Twenty-eight low anxiety (LA) and thirty-one high anxiety (HA) individuals performed a video-recorded Stroop color-word interference test. Heart rate, skin conductance level, finger temperature, electromyographic activity of gastrocnemius and trapezius muscles were recorded; state anxiety and valence of thought content were assessed. Physiological activity increased during the stressful situation, whatever the group. However, prolonged gastrocnemius muscle tension and prolonged decrease in finger temperature were found in HA subjects after the stressful situation, but not in LA subjects. These results suggest that physiological recovery following a moderate cognitive stressor could depend on trait anxiety level.

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Compact tactile matrix (CTM) is a vibrotactile device composed of a seven-by-seven array of electromechanical vibrators "tactip" used to represent tactile patterns applied to a small skin area. The CTM uses a dynamic feature to generate spatiotemporal tactile patterns. The design requirements focus particularly on maximizing the transmission of the vibration from one tactip to the others as well as to the skin over a square area of 16 cm (2) while simultaneously minimizing the transmission of vibrations throughout the overall structure of the CTM. Experiments were conducted on 22 unpracticed subjects to evaluate how the CTM could be used to develop a tactile semantics for communication of instructions in order to test the ability of the subjects to identify: 1) directional prescriptors for gesture guidance and 2) instructional commands for operational task requirements in a military context. The results indicate that, after familiarization, recognition accuracies in the tactile patterns were remarkably precise for more 80% of the subjects.

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The aim of this study was to examine the adaptive process of muscular responses in healthy subjects over two repeated exposures to the same moderate cognitive stressor. The electromyographic (EMG) activity of the flexor pollicis brevis, biceps brachii, triceps brachii, trapezius, gastrocnemius and soleus muscles was recorded in 35 males during video-recorded Stroop color-word interference tests. The results showed lower EMG activity in all muscles during the second exposure to the stressful task, but not in the trapezius muscle. These findings could help to the understanding of the role of stressful situations in the development of musculoskeletal disorders.

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Recent studies have highlighted interactions between state anxiety, sensory processing involved in motor performance, and personality traits such as trait anxiety. In the present study, we investigated the effects of moderate state anxiety on static balance performance with eyes open and eyes closed in two groups of healthy subjects with contrasting trait anxiety. We found that an anxiogenic condition induces larger and faster body swaying in both groups in the eyes-open test. This suggests that state anxiety could modify the processing of the different sensory inputs involved in balance control whatever the subjects' trait anxiety level. When vision is absent, precision of static balance control in individuals with intermediate level of trait anxiety - characterized by a higher visual dependence - is more disrupted than in low trait anxiety subjects. Moreover, moderate state anxiety seems to disturb the ability to use vestibular and/or somatosensory inputs in individuals with low anxiety, but not in individuals with intermediate trait anxiety. These results on inter-individual differences provide a first insight into the inter-dependence between trait anxiety, state anxiety and static balance control.

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OBJECTIVE: To address the question of the space sensorimotor representation during hand-writing and its modifications with aging. We have chosen to study the drawing ellipses without visual guidance. We hypothesized that the decreased manual dexterity associated with aging could be attributed, in part, to the modification of space representation for action. METHODS: Young and elderly subjects drew ellipses with the tip of the index in the three anatomical planes: sagittal, frontal and horizontal. The 3D movements were recorded by a portable Video Recorder (3DVR) adapted to a clinical examination room with a natural light source. RESULTS: All subjects showed large disparities in errors in the various planes. Errors were maximal in the horizontal plane. These findings confirm the assumption of an anisotropic action-related representation of space when the movement is performed in a peripersonal frame of reference. Compared with young subjects, the results demonstrate that aging is associated with an important decreased ability to draw precisely ellipses in the three body-defined reference frames. CONCLUSION: Space representation is altered with aging. This finding supports the idea that the central nervous system is apparently able to maintain hand-drawing performance at a good level independently of the anisotropic character of the egocentric space. SIGNIFICANCE: These findings may contribute to introducing new functional clinical tests and open new perspectives for future investigations on the age-related changes in hand function.

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Previous studies have shown that anxiety and balance disorders could be related; however, the association between psychological processes and equilibrium remains ambiguous. In this study, we have examined whether mood states and anxiety may influence the ability to use the somatosensory, visual and vestibular systems and affect balance control in healthy subjects. Seven male students were submitted to a program testing equilibrium over a 12-day period, during which moods and anxiety states were assessed using self-evaluated questionnaires. Significant negative correlations were found between moods, including anxiety, and the subject's sensory and motor systems of balance control, suggesting that low moods may alter balance performance. However, depending on the type of mood, it is likely that adverse changes in mood states may affect balance in different ways, either through the sensory organization or motor control.

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