Effect of haptic supplementation on postural stabilization: A comparison of fixed and mobile support conditions

International audienceIt is well known in the literature of haptic supplementation that a "light touch" (LT) with the index finger on a stable surface increases postural stability. In view of potential application in the domain of mobility aids, it should however be demonstrated that haptic supplementation is effective even when provided by an unstable stick support. The present study aimed to explore the stabilizing effect of a three-digit "light grip" (LG) of different supports (fixed or mobile stick) in young people. Eleven participants (M = 25.9 years) were tested in an upright standing task in six experimental conditions in which the mobility of the given support and its resistance in opposite direction to the body movement were manipulated. The RMS variability and the range of postural oscillations were measured. The results confirmed that the stabilizing effect of haptic supplementation is independent from the nature of the support (fixed or mobile) when sufficiently large sway-related contact forces on the fingers are provided. Future applications of this "mobile stick paradigm" to complex situations while targeting different groups of participants may help to approach everyday life situations in which an informational stick could potentially be of assistance to gain stability and mobility

Sequential difficulty effects in cognitive and sensorimotor tasks: Insights from arithmetic and Fitts' task

International audienceThe present study tested sequential difficulty effects (SDEs) in arithmetic problem solving and Fitts’ aiming task for the same individuals. SDEs refer to poorer performance on current items following harder items relative to after easier items. Young and older adults accomplished a computational estimation task (i.e., finding the approximate products to two digit multiplication problems) and a Fitts aiming task (i.e., performing rapid pointing movements to reach the finish areas). Current items were preceded by two easy or difficult items (i.e., in the repeate precursor condition) or only one easy or difficult item (i.e., in the unrepeated precursor condition). Participants’ performance revealed SDEs in both the arithmetic and the aiming tasks only when the precursor items were repeated. Data also revealed comparable SDEs in both age groups during the arithmetic task, but SDEs only in older adults while participants accomplished the aiming task. These findings have a number of implications for our understanding of mechanisms underlying SDEs and age-related differences in SDEs, as they suggest that SDEs involve both domain general and domain specific mechanisms that are differentially influenced by aging

Bimanual training in stroke: How do coupling and symmetry-breaking matter?

<p>Abstract</p> <p>Background</p> <p>The dramatic consequences of stroke on patient autonomy in daily living activities urged the need for new reliable therapeutic strategies. Recently, bimanual training has emerged as a promising tool to improve the functional recovery of upper-limbs in stroke patients. However, who could benefit from bimanual therapy and how it could be used as a part of a more complete rehabilitation protocol remain largely unknown. A possible reason explaining this situation is that coupling and symmetry-breaking mechanisms, two fundamental principles governing bimanual behaviour, have been largely under-explored in both research and rehabilitation in stroke.</p> <p>Discussion</p> <p>Bimanual coordination emerges as an active, task-specific assembling process where the limbs are constrained to act as a single unit by virtue of mutual coupling. Consequently, exploring, assessing, re-establishing and exploiting functional bimanual synergies following stroke, require moving beyond the classical characterization of performance of each limb in separate and isolated fashion, to study coupling signatures at both neural and behavioural levels. Grounded on the conceptual framework of the dynamic system approach to bimanual coordination, we debated on two main assumptions: 1) stroke-induced impairment of bimanual coordination might be anticipated/understood by comparing, in join protocols, changes in coupling strength and asymmetry of bimanual discrete movements observed in healthy people and those observed in stroke; 2) understanding/predicting behavioural manifestations of decrease in bimanual coupling strength and/or increase in interlimb asymmetry might constitute an operational prerequisite to adapt therapy and better target training at the specific needs of each patient. We believe that these statements draw new directions for experimental and clinical studies and contribute in promoting bimanual training as an efficient and adequate tool to facilitate the paretic upper-limb recovery and to restore spontaneous bimanual synergies.</p> <p>Summary</p> <p>Since bimanual control deficits have scarcely been systematically investigated, the eventual benefits of bimanual coordination practice in stroke rehabilitation remains poorly understood. In the present paper we argued that a better understanding of coupling and symmetry-breaking mechanisms in both the undamaged and stroke-lesioned neuro-behavioral system should provide a better understanding of stroke-related alterations of bimanual synergies, and help clinicians to adapt therapy in order to maximize rehabilitation benefits.</p

<p>Cognitive functioning enhancement in older adults: is there an advantage of multicomponent training over Nordic walking?</p>

International audienceIntroduction: We compared Nordic walking training (NW) to a multicomponent training (MCT) program of an equivalent intensity, in older adults. Our main hypothesis was that MCT would result in larger effects on cognitive processes than NW. Methods: Thirty-nine healthy older adults, divided into two groups (NW and MCT), took part in the study (17 males, 22 females, mean age =70.8±0.8 years). They were tested for cardiovascular fitness, motor fitness and cognitive performance during the two weeks preceding and following the 12-week training session (3 times/week), respectively. For both the NW and MCT interventions, the training sessions were supervised by a trainer. Heart rate of participants was monitored during the sessions and then used to make training loads as similar as possible between the two groups (TRaining IMPulse method). Results: Results showed that training resulted in better performance for cardiovascular and motor fitness tests. Among these tests, only two revealed a significant difference between the two groups. The NW group progressed more than the MCT group in the 30 Seconds Chair Stand test, while in the One Leg Stance test, the MCT group progressed more. For the cognitive assessment, a significant effect of training was found for executive functions, spatial memory score, and information processing speed response time, with no differences between the two groups. Conclusion: The study confirmed that physical exercise has a positive impact on cognitive processes with no advantage of MCT intervention over NW training. A possible reason is that NW intervention not only improved cardiovascular capacities, but also motor fitness, including coordination capacities

Does bimanual coordination training benefit inhibitory function in older adults?

IntroductionWhether complex movement training benefits inhibitory functions and transfers the effects to non-practiced motor and cognitive tasks is still unknown. The present experiment addressed this issue using a bimanual coordination paradigm. The main hypothesis was that bimanual coordination training allows for improving the involved cognitive (i.e., inhibition) mechanisms and then, transferring to non-practiced cognitive and motor tasks, that share common processes.Methods17 older participants (72.1 ± 4.0 years) underwent 2 training and 3 test sessions (pre, post, and retention one week after) over three weeks. Training included maintaining bimanual coordination anti-phase pattern (AP) at high frequency while inhibiting the in-phase pattern (IP). During the test sessions, participants performed two bimanual coordination tasks and two cognitive tasks involving inhibition mechanisms. Transfer benefits of training on reaction time (RT), and total switching time (TST) were measured. In the cognitive tasks (i.e., the Colour Word Stroop Task (CWST) and the Motor and Perceptual Inhibition Test (MAPIT)), transfer effects were measured on response times and error rates. Repeated one-way measures ANOVAs and mediation analyses were conducted.ResultsResults confirmed that training was effective on the trained task and delayed the spontaneous transition frequency. Moreover, it transferred the benefits to untrained bimanual coordination and cognitive tasks that also involve inhibition functions. Mediation analyses confirmed that the improvement of inhibitory functions mediated the transfer of training in both the motor and cognitive tasks.DiscussionThis study confirmed that bimanual coordination practice can transfer training benefits to non-practiced cognitive and motor tasks since presumably they all share the same cognitive processes

Heterogeneity of time delays determines synchronization of coupled oscillators

Network couplings of oscillatory large-scale systems, such as the brain, have a space-time structure composed of connection strengths and signal transmission delays. We provide a theoretical framework, which allows treating the spatial distribution of time delays with regard to synchronization, by decomposing it into patterns and therefore reducing the stability analysis into the tractable problem of a finite set of delay-coupled differential equations. We analyze delay-structured networks of phase oscillators and we find that, depending on the heterogeneity of the delays, the oscillators group in phase-shifted, anti-phase, steady, and non-stationary clusters, and analytically compute their stability boundaries. These results find direct application in the study of brain oscillations

Deconstructing Emmanuel Levinas’ Aesthetics : A Reading of The Seagram Murals

Emmanuel Levinas on ranskanjuutalainen filosofi, jonka filosofia keskittyy etiikkaan ja toisen kohtaamiseen. Tämä pro gradu keskittyy Levinaksen estetiikkaan, joka on riippuvainen hänen ”ensimmäisestä filosofiastaan”, eli etiikasta. !Työn tutkimuskysymykset ovat Kuinka Levinaksen estetiikka on muodostunut sekä kuinka Mark Rothkon Seagram Murals-maalauksia tulisi arvioida Levinaksen estetiikan pohjalta. Tämän lisäksi työ pohdiskelee juutalaisen filosofian mahdollisuutta ja fiosofian luonnetta. !Pro gradussa arvioidaan ensin Levinaksen laajempaa filosofiaa feministisen dekonstruktion avulla, joka paljastaa filosofian näennäisen rationaalisuuden ja Levinaksen naisvihamielisen paikantumisen. Tämän jälkeen gradussa arvioidaan Levinaksen estetiikkaa ja pohditaan Levinaksen estetiikan rajoja ensin tarkastelemalla Levinaksen argumenttien koherenttiutta hyväksikäyttäen Jacques Derridan kuva — merkki-analyysia, ja tämän jälkeen soveltamalla feministisen dekonstruktion paljastamia ongelmia spesifisti estetiikkaan. Lopuksi analysoin Mark Rothkon The Seagram murals-maalauksia käyttäen Levinaksen estetiikkaa, sekä vertaan sitä Rothkon omiin kirjoituksiin. !Tämä työ tulee siihen tulokseen, että Levinaksen etiikka sekä estetiikka pohjaa juutalaisuuteen, ja näin ollen on oikeutettua puhua juutalaisesta filosofiasta. Levinaksen etiikkaa kuitenkin heikentää hänen naisvihamielisyytensä, joka heikentää hänen esteettisiä argumenttejaan. Levinaksen pohjalta Rothkoa ja hänen töitään tulisi arvioida mukavuustuotteena, joka ei kuitenkaan täytä Levinaksen eettisen toiminnan määreitä

Le système neuro-musculo-squelettique, considéré comme un système dynamique complexe

Théories de l'auto-organisation, théorie des systèmes dynamiques : comment ce cadre conceptuel permet de rendre compte de l'élaboration et du contrôle des coordinations motrices multi-articulaires et multi-segmentaires en sport. Quelques pistes de réflexion à l'usage des intervenants en sport