Sébastien Caudron

Does calculating impair postural stabilization allowed by visual cues

AbstractIn many daily situations, balance control is associated with a cognitive activity such as reading or a simple calculation. The objective of this study was to investigate the relationship between these two specific human activities, especially the influence of visual cues and support surface stability on body sway during a calculation task. A Sensory Organization Test, which can disrupt or suppress sensory inputs, was performed on 71 healthy young adults. The evaluations were performed both with and without mental arithmetic tasks which consisted of backward counting by three or thirteen. Our results showed that the addition of a calculation task induced an increase in body sway only when visual cues were available. They also showed the same instability effect of the support surface on the amount of body sway no matter what the associated cognitive task was. Moreover, no difference in body sway was observed between the two calculation tasks no matter what the visual context and/or the stability of the support surface were. We suggest that focusing on fulfilling the requirements of the mental calculation challenge may be responsible for the increase in body sway. This increase may be related to the use of oculomotor activity as unintentional attempts to increase arousal by self-generated body movement. Thus, this activity facilitates information processing rather than minimizing unbalance by a visual anchor point.

Attenuation of the evoked responses with repeated exposure to proprioceptive disturbances is muscle specific

In response to repetitive proprioceptive disturbances (vibration) applied to postural muscles, the evoked response has been shown to decrease in amplitude within the first few trials. The present experiment investigated whether this attenuation of the response to vibration stimulation (90Hz, 5s) was muscle specific or would be transferred to the antagonist muscles. Sixteen participants stood upright with eyes closed. One half of the participants practiced 15 tibialis vibrations followed by 15 calf vibrations (TIB-CALF order), while the other half practiced the opposite order (CALF-TIB order). Antero-posterior trunk displacements were measured at the level of C7 and centre of foot pressure (COP). EMG activity of the tibialis anterior (TA) and gastrocnemius lateralis (GL) was also measured. Results showed that evoked postural responses as well as EMG activity decreased with practice when vibration was applied to either calf or tibialis muscles. However, such attenuation of the response appeared muscle specific since it did not generalise when the same vibration stimulus was later applied onto the antagonist muscles.

Perception of body movement when real and simulated displacements are combined

Muscle-tendon vibration has often been used to study the contribution of proprioception to kinesthesia and postural control. This technique is known to simulate the lengthening of the vibrated muscle and, in the presence of balance constraints, evoke compensatory postural responses. The objective of the present study was to clarify the consequences of this stimulation on the dynamic features of whole-body movement perception in upright stance and in the absence of balance constraints. Eleven participants were restrained in a dark room on a motorized backboard that was able to tilt the upright body around the ankle joints. The participants were passively tilted backwards or forwards with a maximum amplitude of four degrees and at very low acceleration (thus preventing the semicircular canals from contributing to movement perception). In half the trials, the body displacement was combined with continuous vibration of the Achilles tendons, which simulates a forward tilt. Participants used a joystick to report when and in which direction they perceived their own whole-body movement. Our results showed that during backward whole-body displacement, the movement detection threshold (i.e. the minimum angular velocity required to accurately perceive passive displacement) was higher in the presence of vibration, whereas the accuracy rate (i.e. the proportion of the overall trial duration during which the movement was correctly indicated) was lower. Conversely, the accuracy rate for forward displacements was higher in the presence of vibration. In the absence of vibration, forward movement was detected earlier than backward movement. The simulated whole-body displacement evoked by Achilles tendon vibration was therefore able to either enhance or disrupt the perception of real, slow, whole-body tilt movements, depending on the congruence between the direction of real and simulated displacements.

Lasting improvements in left spatial neglect following a protocol combining neck-muscle vibration and voluntary arm movements: a case-study

Abstract Purpose: Beyond promising experimental results of sensory passive stimulations in spatial cognition disorders, some questions still remain regarding interests of these stimulations during the daily activities in neglect. The aim of this case-study was to evaluate the effects of a protocol combining left neck-muscle vibration with daily simple movements, like arm pointing movements, on perceptivo-locomotor deficits in a left spatial neglect patient. Materials and methods: Two neuropsychological tests, one subjective straight-ahead pointing (SSA) test and one wheelchair navigation test were carried out before the combination protocol, immediately after, 1 h later, and 24 h later. Results: The results showed a reduction of neglect spatial bias following the protocol lasted at least 24 h in all the tests (except for the SSA test due to the unavailability of the pointing device). Conclusions: The range of improvements in the symptoms of spatial neglect suggests that this therapeutic intervention based on the combining neck-muscle vibration to voluntary arm movements could be a useful treatment for this condition. One of future investigation axes should be the development of a vibratory tool in order to facilitate the combining this proprioceptive stimulation to daily activities. Implications for rehabilitation Spatial neglect is a perplexing neuropsychological syndrome, affecting different domains of spatial cognition and impacting also the functional domain. The treatments based on neck-muscle vibration are simple to use, non-invasive and requires none active participation of patient. A therapeutic intervention based on the combining left neck-muscle vibration and voluntary arm movements in a left-spatial-neglect show a lasting reduction of symptoms especially in daily activities. The combination of treatments based on the Bottom–Up approach opens innovative perspectives in rehabilitation.

Mobility may impact attention abilities in healthy term or prematurely born children at 7-years of age: protocol for an intervention controlled trial

BackgroundSeven years of age is a milestone for learning basic knowledge that is strongly related to attention abilities such as Alerting, Orienting, and Inhibition function, allowing for appropriate adaptation to primary school. These attention abilities are also influenced by gestational age at birth in a complex manner, indicating an area of weakness in prematurely born children. Furthermore, recent studies suggest that allowing children to have freedom of movement during learning may improve their attention level and school performance. The purpose of the present study is to determine the influence of mobility on the attentional components that may impact learning abilities in children aged 7-years who were born at term and prematurely.MethodsThis prospective, randomized, controlled trial will focus on psychometric testing of attentional abilities assessed with the Attention Network Test for Child (Child ANT) and involves a mixed measurement design. Forty-eight children aged 7-years, half of whom were premature at birth and in their expected grade without learning difficulties will be included after parental consent. They will be equipped with a head-mounted display in which the Child ANT will be presented. The association of different flankers and pre-cues will allow the measurement of the development level of Alerting, Orienting, and Inhibition function. The task will be composed of one experimental block of trials randomly performed per posture: seated, standing, or free.DiscussionThis study will assess the contribution of mobility in specific attentional contexts that are usually present during fundamental learning in children. New pedagogical formats of teaching could consider these findings, and new pedagogical tools enabling free spontaneous child mobility might be designed. Moreover, a small percentage of children integrating into the educational system are born prematurely. These children, often considered immature and hyperactive, could benefit from educational innovations that enhance their attention abilities, thereby improving their adaptation to primary school.Trial registrationThis trial is registered at ClinicalTrials.gov (NCT03125447).

Visuo-oculomotor skills related to the visual demands of sporting environments

The aim of this study was to assess the visuo-oculomotor skills of gaze orientation in selected sport activities relative to visual demands of the sporting environment. Both temporal and spatial demands of the sporting environment were investigated: The latency and accuracy of horizontal saccades and the gain of the horizontal smooth pursuit of the sporting environment were investigated in 16 fencers, 19 tennis players, 12 gymnasts, 9 swimmers and 18 sedentary participants. For the saccade test, two sequences were tested: In the fixed sequence, participants knew in advance the time interval between each target, as well as the direction and the amplitude of its reappearance; in the Freyss sequence however, the spatial changes of the target (direction and amplitude) were known in advance by participants but the time interval between each target was unknown. For the smooth-pursuit test, participants were instructed to smoothly track a target moving in a predictable sinusoidal, horizontal way without corrective ocular saccades, nor via anticipation or head movements. The results showed no significant differences between specificities of selected sporting activities via the saccade latency (although shorter than in non-athletes), contrary to saccade accuracy and the gain of smooth pursuit. Higher saccade accuracy was observed overall in fencers compared to non-athletes and all other sportsmen with the exception of tennis players. In the smooth-pursuit task, only tennis players presented a significantly higher gain compared to non-athletes and gymnasts. These sport-specific characteristics of the visuo-oculomotor skills are discussed with regard to the different cognitive skills such as attentional allocation and cue utilization ability as well as with regard to the difference in motor preparation.