Eye-hand coordination during visuomotor adaptation: effects of hemispace and joint coordination

We previously examined adaptive changes of eye-hand coordination during learning of a visuomotor rotation. Gazes during reaching movements were initially directed to a feedback cursor in early practice, but were gradually shifted toward the target with more practice, indicating an emerging gaze anchoring behavior. This adaptive pattern reflected a functional change of gaze control from exploring the cursor-hand relation to guiding the hand to the task goal. The present study further examined the effects of hemispace and joint coordination associated with target directions on this behavior. Young adults performed center-out reaching movements to four targets with their right hand on a horizontal digitizer, while looking at a rotated visual feedback cursor on a computer monitor. To examine the effect of hemispace related to visual stimuli, two out of the four targets were located in the ipsilateral workspace relative to the hand used, the other two in the contralateral workspace. To examine the effect of hemispace related to manual actions, two among the four targets were related to reaches made in the ipsilateral workspace, the other two to reaches made in the contralateral workspace. Furthermore, to examine the effect of the complexity of joint coordination, two among the four targets were reaches involving a direct path from the start to the target involving elbow movements (simple), whereas the other two targets were reaches involving both shoulder and elbow movements (complex). The results showed that the gaze anchoring behavior gradually emerged during practice for reaches made in all target directions. The speed of this change was affected mainly by the hemispace related to manual actions, whereas the other two effects were minimal. The gaze anchoring occurred faster for the ipsilateral reaches than for the contralateral reaches; gazes prior to the gaze anchoring were also directed less at the cursor vicinity but more at the mid-area between the starting point and the target. These results suggest that ipsilateral reaches result in a better predictability of the cursor-hand relation under the visuomotor rotation, thereby prompting an earlier functional change of gaze control through practice from a reactive to a predictive control.

The influence of M. P. Bryden's work on lateralization of motor skill: Is the preferred hand selected for and better at tasks requiring a high degree of skill?

One question of interest to Dr M. P. Bryden was how skilled motor behaviour, task complexity, and the degree of handedness are linked. His research suggested that there would be dissociation between hand preference and performance for skilled versus unskilled actions. The thought was that "simple" or unskilled tasks such reaching or grasping could be performed equally well by either hand, and thus either could be selected. Skilled tasks such as fine manipulation would be performed best by the preferred hand and thus it would be selected more frequently. Over the past two decades, researchers have attempted to determine whether such a definition of skilled action best encapsulates the specialization of the preferred hand. The current paper will review M. P. Bryden's research on skilled motor behaviour, as well as more recent work, and explore the question of whether the preferred hand is actually superior and preferred for actions requiring manipulation.

Constraints on arm selection processes when reaching: degrees of freedom and joint amplitudes interact to influence limb selection

With an interest in identifying the variables that constrain arm choice when reaching, the authors had 11 right-handed participants perform free-choice and assigned-limb reaches at 9 object positions. The right arm was freely selected 100% of the time when reaching to positions at 30° and 40° into right hemispace. However, the left arm was freely selected to reach to positions at -30° and -40° in left hemispace 85% of the time. A comparison between free- and assigned-limb reaching kinematics revealed that free limb selection when reaching to the farthest positions was constrained by joint amplitude requirements and the time devoted to limb deceleration. Differences between free- and assigned-arm reaches were not evident when reaching to the midline and positions of ±10°, even though the right arm was freely selected most often for these positions. Different factors contribute to limb selection as a function of distance into a specific hemispace.

Integração de informação e reativação da memória: impacto positivo de uma intervenção cognitivo-motora em bebês

OBJETIVO: Investigar os efeitos de uma intervenção cognitivo-motora na integração de informação e reativação da memória de bebês. MÉTODOS: Participaram do estudo 40 bebês de seis a oito meses de idade, nascidos a termo e matriculados em creches, permanecendo nelas sete horas por dia com relação educador/bebê de 1/6, provenientes de famílias numerosas e de baixa renda que não participavam de programas interventivos. Uma intervenção cognitivo-motora foi propiciada ao Grupo Interventivo com atividades de perseguição visual, manipulação de brinquedo e controle postural. Para o Grupo Controle, nenhuma intervenção foi propiciada. As atividades da rotina da creche foram mantidas para os dois grupos. Três atividades de manipulação foram avaliadas no início do programa, um mês depois (retenção) e três dias após a retenção. Para a análise dos dados, foram utilizados o teste do qui-quadrado com correção de Yates, o teste exato de Fisher e o de Cochran. RESULTADOS: O Grupo Interventivo demonstrou desempenho significativamente superior ao Grupo Controle em evocar informações da memória na retenção e pós-retenção em duas atividades. Mudanças significativas e positivas também foram observadas para o Grupo Interventivo no fator tempo. Os bebês mais velhos do Grupo Interventivo demonstraram melhor capacidade de evocar informação em relação aos mais jovens. Essa tendência não foi observada para o Grupo Controle. CONCLUSÕES: Para potencializar o desenvolvimento global de bebês, as intervenções deveriam ser organizadas implementando tarefas diversificadas com intervalos de aprendizagem apropriados, os quais levem em consideração a capacidade dos bebês de manterem a informação e integrarem essa informação a novos desafios

Straight ahead acts as a reference for visuomotor adaptation

One can adapt movement planning to compensate for a mismatch between vision and action. Previous research with prismatic lenses has shown this adaptation to be accompanied with a shift in the evaluation of one's body midline, suggesting an important role of this reference for successful adaptation. This interpretation leads to the prediction that rotation adaptation could be more difficult to learn for some directions than others. Specifically, we hypothesized that targets seen to the right of the body midline but for which a rotation imposes a movement to its left would generate a conflict leading to a bias in movement planning. As expected, we observed different movement planning biases across movement directions. The same pattern of biases was observed in a second experiment in which the starting position was translated 15 cm to the right of the participants' midline. This indicates that the "straight ahead" direction, not one's midline, serves as an important reference for movement planning during rotation adaptation.