Time course of timing reprogramming in interception is modulated by uncertainty on velocity alteration
Luis Teixeira*
Mariana Franzoni
University of São Paulo, School of Physical Education and Sport, Brazil.
ABSTRACT
Reprogramming of interceptive actions is required when an abrupt unexpected modification in target velocity takes place. In such a situation, the original timing specifications have to be replaced by other ones appropriate for the new characteristics of the target motion in a short period of time. In this study, we contrasted two sources of uncertainty on target velocity modification in an interceptive task, probability and direction of change, and analyzed the time course of movement timing reprogramming. Participants tried to synchronize the action of hitting a hemiball with the arrival of a moving target at the end of an electronic trackway. The target was initially displaced at a constant velocity of 3 m/s, and in some trials its velocity was unexpectedly changed to 2 m/s or 4 m/s at different moments before interception. Participants were assigned to one of two groups: 25% or 50% probability of target velocity alteration, with both groups facing conditions of uni and bidirectional velocity change. The results showed a gradual increment of temporal accuracy as a function of longer times after velocity change, revealing the continuous nature of timing reprogramming. The lowest uncertainty condition led to the best movement reprogramming, producing more accurate timing responses throughout situations of changed velocity.
]]> Key Words: movement reprogramming, continuous models, moving targets, sensorimotor control.
RESUMO
O curso de tempo da reprogramação temporal em tarefa interceptativa é modulado pela incerteza sobre a mudança de velocidade.
Quando ocorre uma mudança abrupta e inesperada na velocidade de um alvo móvel em tarefas interceptativas, torna-se necessária a reprogramação do ato motor. Em tal situação, as especificações originais de temporização do movimento devem ser substituídas por outras apropriadas às novas características de deslocamento do alvo em um curto intervalo de tempo. Neste estudo contrastámos duas fontes de incerteza sobre a modificação de velocidade do alvo em uma tarefa interceptativa, probabilidade e direção de mudança, e analisamos o curso de tempo para reprogramação do componente temporal. Os participantes tentaram sincronizar a ação de contatar uma hemibola com a chegada de um estímulo móvel ao final de um trilho eletrônico. O estímulo foi deslocado inicialmente com uma velocidade constante de 3 m/s, e em algumas tentativas sua velocidade foi inesperadamente alterada para 2 m/s ou para 4 m/s em diferentes momentos antes da interceptação. Os participantes foram distribuídos em dois grupos: 25% ou 50% de probabilidade de mudança de velocidade, sendo que ambos os grupos foram submetidos às condições de mudança unidirecional e bidirecional de velocidade. Os resultados mostraram um aumento gradual da precisão temporal em função de períodos mais longos após a mudança de velocidade, revelando a natureza contínua da reprogramação motora. A condição de menor incerteza levou à melhor reprogramação, resultando em respostas temporalmente mais precisas através das situações de mudança de velocidade.
Palavras-chave: reprogramação motora, modelos contínuos, alvos móveis, controle sensoriomotor.
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]]> CORRESPONDÊNCIA
*Luis Augusto Teixeira
Escola de Educação Física e Esporte
Universidade de São Paulo
Av. Prof. Mello Moraes, 65
05508-900 - São Paulo, S.P.
Brasil
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