BCI-Based Control for Ankle Exoskeleton T-FLEX: Comparison of Visual and Haptic Stimuli with Stroke Survivors.

Brain-computer interface (BCI) remains an emerging tool that seeks to improve the patient interaction with the therapeutic mechanisms and to generate neuroplasticity progressively through neuromotor abilities. Motor imagery (MI) analysis is the most used paradigm based on the motor cortex's electrical activity to detect movement intention. It has been shown that motor imagery mental practice with movement-associated stimuli may offer an effective strategy to facilitate motor recovery in brain injury patients. In this sense, this study aims to present the BCI associated with visual and haptic stimuli to facilitate MI generation and control the T-FLEX ankle exoskeleton. To achieve this, five post-stroke patients (55-63 years) were subjected to three different strategies using T-FLEX: stationary therapy (ST) without motor imagination, motor imagination with visual stimulation (MIV), and motor imagination with visual-haptic inducement (MIVH). The quantitative characterization of both BCI stimuli strategies was made through the motor imagery accuracy rate, the electroencephalographic (EEG) analysis during the MI active periods, the statistical analysis, and a subjective patient's perception. The preliminary results demonstrated the viability of the BCI-controlled ankle exoskeleton system with the beta rebound, in terms of patient's performance during MI active periods and satisfaction outcomes. Accuracy differences employing haptic stimulus were detected with an average of 68% compared with the 50.7% over only visual stimulus. However, the power spectral density (PSD) did not present changes in prominent activation of the MI band but presented significant variations in terms of laterality. In this way, visual and haptic stimuli improved the subject's MI accuracy but did not generate differential brain activity over the affected hemisphere. Hence, long-term sessions with a more extensive sample and a more robust algorithm should be carried out to evaluate the impact of the proposed system on neuronal and motor evolution after stroke.

Haptic information provided by anchors and the presence of cognitive tasks contribute separately to reducing postural sway in young adults.

BACKGROUND: Haptic information provided by the anchors reduces postural sway while standing upright. It is unclear whether this benefit would remain in the presence of cognitive tasks combined with a more challenging postural task. RESEARCH QUESTION: Our aim was to investigate the effects of the anchors and visual and auditory cognitive tasks on postural control in young adults in a challenging balancing task. METHODS: Twenty young adults stood upright on a balance beam with the central portion of each foot placed over the beam and feet at shoulder width without and with the use of the anchors in three cognitive conditions: control, visual Stroop task, and auditory digit-monitoring task. Each anchor consisted of a flexible cable with a light load (125 g) attached at one end of the cable. With the anchors, the participants held the flexible cable in each hand with the light load resting on the ground while keeping tension in the cable. RESULTS: Both visual and auditory cognitive tasks reduced the center of pressure (COP) ellipse area, the root mean square of the margin of dynamic stability (based on the extrapolated center of mass, COM) and increased the COM time-to-contact relative to the boundaries of the base of support in the AP direction. The anchors reduced the COP ellipse area. SIGNIFICANCE: There is a functional integration between postural control and cognitive tasks, such that postural sway was reduced to facilitate the execution of the cognitive tasks. Anchors were effective in reducing postural sway, suggesting that haptic information was able to benefit postural control in a challenging balancing task regardless of the cognitive task.

Modulation of Cortisol Responses to an Acute Stressor in Zebrafish Visually Exposed to Heterospecific Fish During Development.

Studies regarding predator-prey relationships have often focused on prey assessment and the responses to predation risk, but few have verified the relationship in the presence or absence of visual contact with a predator (e.g., tiger oscar, Astronotus ocellatus) or a nonpredator (e.g., goldfish, Carassius auratus) during the developmental phase, which could alter several physiological and neuroendocrine mechanisms in adulthood. Herein, we determined responses to physical (chasing with a net) and biological stressors (visualization to predator) in adult zebrafish raised in visual contact with a predator or nonpredator fish. We demonstrated that adult naive zebrafish show a more intense cortisol stress response than fish housed in visual contact with the stimulus fish (predator or nonpredator) when larvae, and that this alteration is related with movement specificity of the stimulus fish.

The Influence of Different Performance Level of Fencers on Simple and Choice Reaction Time / A influência dos diferentes níveis de desempenho dos esgrimistas no tempo de reação simples e de escolha

Abstract In many sport disciplines reaction time plays a key role in the sport performance. It is good to point out for example ball games or fighting sports (fencing, karate etc.). The research is focused on detection of the differences in the simple and choice reaction time during visual stimulation among elite, sub-elite fencers and beginners. For the measurement a Fitrosword device and the SWORD software were used. An additional stimulus was added during measuring which should increase the overall number of stimuli, but shouldn’t force fencer to any reaction whatsoever. The results from presented study can be compared with Hicks law. The next focus of the study was to identify the difference in reaction time during two different movement tasks with different complexity movement requirements. The research was built up on a hypothesis that the results will differ among different performance groups of fencers. The difference however was overt among beginners and elite fencers (p = 0.0088, d = 0.5) in reaction time during different movement tasks (direct hit vs. lunge). The results of this research could be useful to trainers for training process organisation and increase the effectivity of muscle coordination during several movements in fencing.

Resumo Em muitos desportos, o tempo de reação desempenha um papel crucial no resultado desportivo. Como exemplo, pode-se citar jogos que envolvam bola ou desportos de combate (esgrima, karate, etc). A pesquisa foca-se na detecção das diferenças entre os tempos de reação simples e de escolha durante os estímulos visuais entre esgrimistas de elite, sub-elite e iniciantes. Para a medição foram usados um aparelho de Fitrosword e o software SWORD. Foi ainda adicionado um estímulo extra durante as medições que leva em consideração o número total de estímulos, sem, no entanto, forçar o esgrimista a esboçar qualquer reação. Os resultados deste estudo podem ser comparados com a lei de Hicks. O próximo objetivo do estudo foi identificar a diferença no tempo de reação entre duas tarefas de movimento diferentes com diferentes exigências no tipo de complexidade motora. A investigação foi formulada sobre a hipótese de que os resultados irão divergir entre os diferentes grupos de esgrimistas. A diferença (p = 0.0088, d = 0.5) foi evidente entre os iniciantes e os de elite no tempo de reação durante as diferentes tarefas motoras (golpe directo vs. ataque). Os resultados desta investigação poderão ser úteis para os treinadores no seu esquema de treinos e aumentar a eficácia da coordenação muscular durante os vários movimentos na esgrima.