Pouco se conhece ainda sobre as demandas atencionais necessárias para o equilíbrio em condições desafiantes, como em situação de postura perturbada. Respostas posturais podem ser influenciadas por tarefas supraposturais. Tarefas de estabilidade manual parecem induzir respostas posturais mais eficientes. Já as tarefas supraposturais cognitivas apresentam resultados incongruentes nos efeitos em tarefa postural perturbada. Este estudo procurou determinar os efeitos de realizar diferentes tipos de tarefa suprapostural nas respostas posturais reativas a uma perturbação mecânica. Vinte e cinco adultos jovens foram sujeitos a uma perturbação mecânica, com liberação de carga, imprevisível. Concomitantemente com essa tarefa postural, realizaram uma tarefa de estabilidade manual, que requeria segurar uma bandeja com cilindro, em uma de duas variantes: com superfície plana para baixo, ou com superfície redonda para baixo. Os participantes realizaram ainda uma tarefa cognitiva, de contagem decrescente de três em três. Essa tarefa foi desempenhada em conjunto com a tarefa dual descrita anteriormente e ainda de forma isolada. A realização da multitarefa prejudicou o desempenho na tarefa cognitiva e também na tarefa postural. Foi observado maior número de erros e maior tempo médio para responder à tarefa cognitiva. Na tarefa postural foram encontradas diferenças nas estratégias motoras quando foi solicitada a tarefa cognitiva: maiores amplitudes de flexão articular no quadril e ombro, maior deslocamento linear do tronco, maior velocidade do tronco e da bandeja bem como menor magnitude do gastrocnêmio. Nesta condição os participantes também demoraram mais para reverter a oscilação anterior e assim retornar a uma posição mais estável. Assim a integração entre as tarefas não foi bem sucedida, por interferência nos processos e/ou recursos atencionais necessários para realizar as tarefas. É possível que tenha ocorrido afastamento de recursos atencionais do processamento de inputs sensoriais associados ao controle postural. Tal afetaria o central set, produzindo uma influência imprecisa nas respostas posturais à perturbação. A tarefa manual produziu efeito positivo na tarefa postural. Observou-se que a condição de maior restrição da tarefa manual induziu uma resposta postural mais eficiente, com menor amplitude articular do ombro, quadril e tornozelo. Verificou-se ainda que as medidas referentes à mobilização do tronco: amplitude linear, velocidade e verticalidade, bem como a velocidade da bandeja, também foram menores. Este estudo indica que o central set é elaborado a partir de restrições funcionais impostas por tarefas supra-posturais e consegue exercer algum controle na tarefa postural, mesmo com um processamento paralelo para realizar uma tarefa cognitiva. A competição entre os processos e\\ou recursos para realizar as tarefas propostas no presente estudo afeta o equilíbrio, de forma negativa quando uma tarefa cognitiva está presente, e de forma positiva quando existe uma restrição funcional manual / Attentional demands on posture challenging conditions still present many questions. Postural answers can be influenced by suprapostural tasks. Motor tasks and, specifically, manual stability tasks induce more efficient postural answers. Cognitive suprapostural tasks present incongruent effects on perturbed posture. This study aimed to determine the effects of performing different suprapostural task types on reactive postural answers. Twenty five received a mechanical perturbation through unpedictable load liberation. Concurrently to this postural task, they performed a manual stability task, to hold a cylinder on a tray, with two variations: with the flat surface down or with the round surface down. Participants also performed a cognitive task, the n-back 3 task. This task was performed as a single task and concomitantly with the dual task. Performing multitask impaired cognitive and postural task performance. More errors and greater mean time to answer to the cognitive task were observed. At the postural task we found differences on motor strategies on the cognitive task condition: greater joint flexion at hip and shoulder, greater trunk linear displacement, greater trunk and tray velocity, as well as a reduction on gastrocnemius magnitude. At this condition we also found that the participants took longer to revert the anterior oscilation to return to a more stable position. Therefore the integration between tasks was successful, given the interference between the attentional processes and/or necessary resources to accomplish the tasks. It is possible that may have been withdrawal of attentional resources form the sensorial inputs processing associated with the postural control. That would affect central set, producing an inaccurate influence on postural answers to perturbation. Manual task produced positive effect on postural task. On the higher restriction condition it was found a more efficient postural answer, with less joint range on shoulder, hip and ankle. Additionally, the trunk variables: linear displacement, velocity and verticality, as well as tray velocity, also were inferior. This study indicates that central set is elaborated based on functional restrictions imposed by suprapostural tasks and it can influence postural task, even with a parallel processing in order to execute a concomitant cognitive task. Competition between processes and/or resources to accomplish the proposed tasks affects balance, with negative results when a cognitive task is present, and with positive results when there is a manual restriction

It is well established that aging is associated with numerous health concerns, including poor balance. Deteriorations in attention demand also place older adults at a greater risk for falls. Emerging experiments have explored the impact of dual-task training programs and have improved dual-tasking in older adults. However, it is unknown whether these performance-related improvements are a function of the intervention itself or the repeated exposure to the testing protocol. Study 1 explored the implications of repeated administration, once per week for 5 weeks, of a protocol involving standing postural sway while concurrently performing reaction time (RT) tasks in older adults. Results revealed that postural sway was stable across testing sessions whereas the difficult RT task gradually improved over time. Study 2 examined the influence of repeated exposure, once per week for 5 weeks, of a protocol involving negotiating a series of obstacles while performing RT tasks in older adults. Participants walked significantly faster with repeated exposure and gradually improved RT. Study 3 investigated the impact of repeated exposure, once per week for 5 weeks, to three functional mobility measures in older adults. It also examined the influence of a 12-week balance and mobility training (BMT) program as well as a 12-week balance and mobility plus cognitive training (BMT+C) program on functional mobility in older adults. Functional mobility served to be stable over time. Both the BMT and BMT+C groups significantly improved functional mobility and sustained these improvements at the 12-week follow-up, while no changes were observed in the control group. No differences between the BMT and BMT+C groups emerged. Experiment 4 examined the influence of BMT and BMT+C on postural sway and RT in older adults. Participants in both training groups significantly improved RT and sustained these improvements at the follow-up, while no changes were observed in the control group. No changes to postural control were shown in any group. No differences between the BMT and BMT+C groups emerged. Experiment 5 examined the influence of BMT and BMT+C on negotiating a series of obstacles while performing RT tasks in older adults. Both the BMT and BMT+C groups significantly improved RT and sustained these improvements at the follow-up, while no changes were observed in the control group. All groups showed faster time to completion of the obstacle series. No differences between the BMT and BMT+C groups emerged. Collectively, these findings suggest that BMT and BMT+C significantly improve functional mobility and divided attention, and sustain these improvements over time. Although some improvements were observed after repeated exposure over 5 weeks, no changes in the control group were observed. Therefore, the improvements exhibited from BMT and BMT+C are likely not a function of repeated exposure to the testing protocol, as participants may be more susceptible to performance-related improvements when the testing sessions are close in proximity. Altogether, these findings propose that, whether or not cognitive training is included, attention demanding dual-task training not only improves functional mobility and RT, but also sustains these improvements over time in older adults. These results may be used to improve the prescription of exercise in older adults.

While stepping in place without vision, individuals displace linearly and rotate, without perceiving these displacements. The aims of this study were to evaluate the effect of a concomitant cognitive task and the influence of knee height on these displacements in stepping in place for 50 steps. Sixteen adults (mean age = 22 years) performed four conditions of stepping: normal knee height and high knee height with and without a cognitive task. Antero-posterior (AP) displacement was significantly smaller in dual task than in single task at normal knee height, and AP and medio-lateral displacements were significantly larger at high than at normal knee height for single and dual task. No changes in body rotation were found. These findings suggest that automaticity is involved in the control of stepping in place with a concurrent cognitive task and that one’s attentional capacity is exceeded when stepping in place with high knees and a cognitive task.

O presente estudo teve como objetivo avaliar a aprendizagem em uma tarefa dual em comparação à aprendizagem de tarefas singulares e a respectiva variação de demanda atencional em função da prática. Participaram do estudo 27 estudantes universitários destros, divididos em três grupos de acordo com a tarefa praticada: prática da tarefa singular de traçar uma estrela com a mão esquerda recebendo feedback invertido (EST), prática da tarefa singular de toques sequenciais dos dedos da mão direita (TOQ) e prática dual consistindo na prática simultânea das duas tarefas singulares (T+E). A demanda atencional foi mensurada por meio do tempo de reação probatório, com estímulo auditivo e resposta vocal. As tarefas foram praticadas em 200 tentativas, distribuídas em 4 sessões executadas em diferentes dias. O efeito de aprendizagem foi avaliado após um dia e após uma semana a última sessão de prática. Os resultados mostraram que a demanda atencional foi maior na tarefa dual em comparação com as tarefas singulares e houve diminuição persistente da demanda atencional após o período de prática somente para a tarefa dual. A análise da fase de aquisição mostrou que o ganho proporcional de desempenho do grupo T+E foi equivalente ao encontrado para os grupos singulares, apesar de ter havido vantagem de desempenho favorável aos grupos singulares. A avaliação da retenção revelou que a prática na tarefa dual induziu resultados equivalentes à prática nas tarefas singulares quando avaliado o desempenho em cada tarefa motora separadamente. Para desempenho na tarefa dual, o grupo T+E atingiu valores superiores ao grupo EST e valores equivalentes ao grupo TOQ nas respectivas tarefas praticadas por estes dois grupos. Tais resultados mostram que o compartilhamento dos recursos atencionais durante a tarefa dual não prejudicou a aprendizagem motora em comparação com a prática com atenção focal em uma tarefa singular / This study aimed to evaluate learning of a dual task in comparison to learning of single tasks and the respective variation of attentional demand as a function of practice. Twenty-seven right-handed university students participated of the study. They were assigned to one of three groups: practice of a single task requiring drawing of a star based on inverted visual feedback with the left hand (EST); practice of a single task requiring fast sequential fingers movements with the right hand (TOQ); and practice of a dual task requiring performance of both single tasks simultaneously (T+E). To evaluate attentional demand we used a probe reaction time task, consisting of auditory stimuli and vocal responses. The experimental tasks were practiced for 200 trials, during four sessions distributed on different days. The learning effect was evaluated after one day and after one week the last practice session. Results showed that attentional demand was higher when performing the dual task in comparison with the two single tasks and reduced attentional demand persisted after the practice period only for the dual task. Analysis of the acquisition phase showed that the proportional performance gain of the T+E group was equivalent to that found for groups practicing single tasks, despite the performance advantage favoring the latter. Evaluation of the retention phase showed that practice of the dual task led to similar results to practicing single tasks when performance was measured on each motor task separately. For performance on the dual task, the T+E group was superior in comparison with the EST group and equivalent to the TOQ group on the specific tasks practiced by these two groups. The results evidenced that sharing attentional resources in the practice of a dual task did not hinder motor learning in comparison to situations of focused attention to the practice of a single task

The postural control-cognition dual-task literature has demonstrated greater postural stability through the examination of multiple kinetic and kinematic measures. Recently, sample entropy (SampEn) and wavelet discrete transform have supported the claim of automaticity, as higher SampEn values and a shift toward higher contribution from automatic sensory systems have been demonstrated in dual-task settings. In order to understand the cortical component of postural control, functional near-infrared spectroscopy (fNIRS) has been used to identify cortical activation under postural control conditions. However, the neural correlates of automatic postural behaviour have yet to be fully investigated. Therefore, the purpose of this study is to confirm the presence of automatic postural control through static and dynamic measurements, and to investigate the prefrontal cortex activation (PFC) when concurrently performing quiet standing and auditory cognitive tasks. Eighteen healthy young adults (21,4 ± 3,96yo), 12 females and 6 males, with no balance deficits were recruited. Participants were instructed to either quietly stand on a force platform (SM), perform three cognitive tasks while seated (SC) and perform a combination of SM and SC concurrently (DT). Results revealed automatic postural control as evidenced by lower area and standard deviation of center-of-pressure in DT conditions. As for SampEn and the wavelet analysis, greater values and a shift from vision to the cerebellum contribution were demonstrated in DT conditions. For the DNS task, a trend toward significantly lower right hemisphere PFC activation compared to left hemisphere activation in DT was evidenced, which potentially reiterate the presence of automaticity. Therefore, as demonstrated by this experiment, the simultaneous performance of a difficult cognitive task and posture yields automatic postural behaviour, and provides insight into the neural correlates of automaticity.

The aim of the study was to investigate the association between working memory capacity and golf performance in a dual-task paradigm. Twenty-eight golfers with ages varying from 19-58 participated in the study. The participants were instructed to, after assessing their working memory capacity with digit span tests, hit ten golf putts from varying distances in two different conditions, one single-task condition (just performing the golf putts) and one dual-task condition (golf putts plus a working memory task). In the dual-task condition the participants were given an address (including street name, postal code and city) to remember while hitting all ten putts. After hitting the putts in each condition the participants reported their perceived mental effort. Results from the study showed that participants with higher working memory capacity performed better than participants with lower working memory capacity in general, but especially in the distracted condition. Results also showed that participants with higher working memory capacity perceived less mental effort compared to participants with lower working memory capacity, especially in the distracted condition. The findings from this study indicate that working memory capacity is related to performance and mental effort exerted during performance, especially in a distracted condition.

Younger adults who are walking and doing additional tasks at the same time may not realize if their performance suffers, putting some at greater risk for injury and impairment during certain tasks. This thesis has addressed this confound by developing a divided attention paradigm focusing on discrete and continuous demand manipulations. The work assessed in motorcognitive processing changes with cerebral and behavioral monitoring of over-ground walking with or without cognitive tasks. Participants (n = 19, 18-35 years, 13 females) were asked to walk at their usual pace [usual walking condition (SM)], walk at their usual pace while performing a cognitive task [dual-task condition (DT)] as well as conduct a cognitive task while standing [single cognitive condition (SC)]. All participants conducted two discrete [simple response time (SRT) & go-no-go (GNG)] and two continuous cognitive tasks [N-back (NBK) & double number sequence (DNS)] of increasing demand. The study revealed significant brain and behavior interactions during the most demanding continuous cognitive task, the DNS. The findings demonstrated lower accuracy rates, slower walk speeds as well as greater cerebral oxygenation in DNS DT in comparison to single task conditions. With increasing cognitive demands and tasks, there were longer response times, as well as lower accuracy rates. The behavioral findings were qualified by marginally significant interactions in a 2 x 4 RM ANOVA between SC-DT task and demand for accuracy rate [F (3, 54) = 2.66, p = 0.06, η2 =.13], significant interactions in response time [F (2, 36) = 4.1, p = 0.026, η2 =.18] as well as significant SM-DT task and demand findings for walk speed [F (3, 54) =5.3, p = 0.003, η2 =.23]. The 2 x 2 x 4 RM ANOVA revealed significant HbO2 interactions between walking tasks (single and dual), hemisphere and demand [F (3, 54) = 5.730, p = 0.002, η2 =.24] in the DNS only. The data suggests that greater demand manipulations with continuous cognitive tasks may be sensitive to both prefrontal cortex (PFC) and behavioral assessments in younger adults (YA). Further validation of the discrete-continuous demand paradigm in motor studies may provide a basis for cognitive assessment with applications in motor learning, cognitive training, aging and more.

Alors que le traitement de nombreuses tâches ordinaires (e.g., parler à son passager, répondre à un e-mail) est en cours, l'apparition d'un stimulus important (e.g., le klaxon d'un voiture) peut nécessiter un traitement prioritaire. Paradoxalement, l'investigation de ce constat dans le champs de la psychologie expérimentale ne rend compte que très rarement compte de la possibilité d'interrompre une action en cours en vue de donner la priorité à une autre réponse motrice. Il apparait donc heuristique d'approfondir les limites et les effets de cette possibilité relativement répandue d'un point de vue écologique. Pour ce faire, nous avons articulé les problématiques inhérentes à l'interférence en double tâche et à l'inhibition motrice afin de mettre au point une série de quatre volets expérimentaux lors desquels la possibilité d'interrompre une réponse non prioritaire en vue de donner la priorité à une autre réponse motrice fut systématiquement donnée aux participants. L'ensemble des résultats convergent vers une diminution de la probabilité d'interruption de la réponse motrice non prioritaire lorsque le stimulus prioritaire apparaît tardivement et peu fréquemment. De plus, le caractère prioritaire d'une tâche motrice ne semble pas constituer un paramètre suffisant permettant d'isoler les processus correspondants de ralentissement. Corollairement, l'interruption de la réponse motrice non prioritaire ne semble pas non plus totalement prémunir le traitement de la tâche prioritaire de ralentissement notamment lorsqu'il n'est pas possible de prédire avec certitude l'apparition du stimulus correspondant. / While many ordinary task processes are ongoing (e.g., to talk with a passenger, answer an e-mail), the apparition of an important stimulus (e.g., a car honking at us) can urge a prioritized process. Paradoxically, investigations about this observation in experimental psychology's field give very few account of the possibility to interrupt a processing action in order to give all priority to another one. Thus, it seems heuristic to deepen the limits and the effects of this widespread possibility from an ecological perspective. To do so, we articulated dual task and motor inibition problematics in order to set up a serie four experimental parts where the possibility to interrupt a low priority response in order to prioritize another response was systematically given to the participants. The whole results converge toward a diminution of the capability to interrupt a low prioritized motor response when the prioritized stimulus appears belatedly and rarely. Moreover, the prioritized nature of a motor task seems to not represent a sufficient parameter alowing isolation of its processes from slowing. As a corollary, interruption of the low prioritized response seems to not prevent the prioritized process from slowing especially when corresponding stimulus apparition is not predictable.

Research in dual task performance varies widely in its methodology and results. The present study employed three different types of activity to provide insights into the interference that occurs in dual task performance. Twenty young adults completed a speech task (repeating a sentence), a verbal fluency task (listing words beginning with the same letter), and right- and left-handed motor tasks (placing pegs and washers in a peg board) in isolation and in concurrent conditions. Speech kinematic data revealed that during concurrent performance of manual tasks, lip displacement and peak velocity decreased, while sound pressure level and spatiotemporal variability increased. The impact of manual motor performance on speech differed between the right and left hand. Manual motor scores significantly decreased when concurrently performed with the verbal fluency task. Also, verbal fluency results declined when performed concurrently with left-handed manual motor task. These findings suggest that cortical localization of control may be more complex than is predicted by the functional distance hypothesis.

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