Biomedical subjects

Luis Augusto Teixeira

Publications and source records attributed to Luis Augusto Teixeira.

6 recordsLinked to original sources

PubMed2006

Intermanual transfer of timing control between tasks holding different levels of motor complexity.

Interlateral transfer of learning was investigated in timing tasks holding different levels of motor complexity. The tasks required hitting a hemiball at the end of an electronic trackway simultaneously with the end of displacement of a visual stimulus. The hemiball was to be hit with the palm of one hand (simple task), or through a forehand drive with a racquet (complex task). Four experimental conditions were compared, which resulted from the combination between direction of transfer for complexity, and direction of transfer for hand. The results evidenced partial interlateral transfer of timing control, and that performance on the transfer task was temporally biased by the practised task. Additionally, there was not a consistent advantage for a single direction of transfer of learning, which means symmetric capacity of intermanual transfer. Such findings indicate that in synchronisation tasks motor learning takes place at two levels: at a higher level independent of the effector system, and at a lower effector-specific level.

Acceleration↗

PubMed2006

Are the elderly able to appropriately reprogram their actions?

Movement reprogramming in a task requiring timing accuracy was investigated in young and elderly individuals. The task consisted of manually hitting a hemiball in synchrony with the arrival of a moving light stimulus running through an electronic trackway. Movement reprogramming was required by unexpectedly changing the regular stimulus velocity at different moments before the due time of arrival at the interception position. Such changes produced times after velocity decrease (TAVD) between 150 ms and 750 ms, representing the periods of time available for generation of new movement timing specifications. Effect of probability of stimulus velocity change was investigated by comparing the conditions of 25% and 50% of chance of velocity decrease. Analysis of performance in conditions of velocity decrease showed an enlargement of temporal error as a function of longer TAVDs up to 300-375 ms. In conditions in which TAVDs were longer than 375 ms young participants showed a progressive improvement of accuracy over time, while the elderly were unable to improve their performance even for a TAVD of 750 ms. A trend toward a more efficient reprogramming with reduced uncertainty was observed only in the young. These results indicate that movement reprogramming is a continuous process in young individuals, but it is impaired in the elderly, preventing an appropriate reorganization of the action.

Adolescent↗

PubMed2005

The continuous nature of timing reprogramming in an interceptive task.

The time course of movement timing reprogramming was examined in a task requiring temporal coincidence of the conclusion of a forehand drive with the arrival of a moving luminous target at the end of an electronic trackway. The moving target departed from one end of the trackway at a constant velocity of 2 m (.) s(-1), and for a part of the trials its velocity was increased to 3 m (.) s(-1). Target velocity was modified at different moments during stimulus displacement, producing times-to-arrival after velocity increment (TAVIs) from 100 to 600 ms. The effect of specific practice on movement reprogramming was also examined. The results showed early adjustments to the action (TAVIs = 100 - 200 ms) that seemed to be stereotyped, while feedback-based corrections were implemented only at TAVIs of 300 ms or longer. Temporal accuracy was progressively increased as longer TAVIs were provided up to 600 ms. Skill training led to an overall increment of temporal accuracy, but no effect of specific practice was found. The results indicate that timing reprogramming in interceptive actions is a continuous process limited mainly by intrinsic factors: latency to initiate more effective adjustments to the action, and rate-of-movement timing reprogramming.

Adaptation, Physiological↗

PubMed2003

Intermanual transfer of force control is modulated by asymmetry of muscular strength.

Interlateral transfer of learning is conceptualized as an index of the degree to which learning takes place at a lower level of motor control, with strong dependence on the effector system, or at a higher effector-independent level in the movement organization hierarchy. In this study, the locus of motor learning was investigated by increasing lateral asymmetry of force between the wrist flexor muscles, and comparing the amount of interlateral transfer of force control in relation to a condition of symmetric force. To perform this contrast, the participants were assigned to one of three groups: symmetric force (SM), who were left with original asymmetries of muscular strength; asymmetric force (AS), who had unilateral training for increment of maximum strength for the wrist flexor muscles; or a control condition (CO). The learning task consisted of launching a small cart across a metallic trackway with the preferred hand, aiming at making the cart achieve an instantaneous velocity of 70 cm/s. This action was practiced for 300 trials by the SM and AS group, while the CO group had active rest. The groups, then, were submitted to a transfer task requiring a mirrored action with the contralateral hand. The results indicated that the SM group achieved significantly higher interlateral transfer of learning as compared to the AS group, which presented response variability similar to the CO group. Analysis of directional trend of error revealed that the AS group presented a significant target overshoot as compared with the symmetric force groups. These findings suggest that an absolute force is learnt at a higher level in the action hierarchy, and that decline in interlateral transfer of learning in the asymmetric force condition was motivated by a resetting in the interplay between higher and lower levels of movement control.

Adult↗

PubMed2003

Reduction of lateral asymmetries in dribbling: the role of bilateral practice.

The influence of bilateral practice on the modification of well-established lateral asymmetries of performance was investigated in overlearned motor skills related to soccer in 12- to 14-year-old adolescent players. The participants had extensive practice before entering the experiment and were trained 2 hours per day, five times per week, during a period of 4 months. In the training, the participants were assigned to one of two groups: practice with emphasis on the preferred leg (PL), or practice with emphasis on the nonpreferred leg (NpL). Lateral asymmetries of performance were assessed before and after training on three motor tasks: kicking for force, kicking for accuracy, and speed of dribbling. The analysis of the results indicated a consistent asymmetry of performance throughout the tests, favouring the preferred leg. The asymmetry of performance was maintained at a constant level across the tests for the kicking tasks in both experimental groups. For speed of dribbling, however, the index of lateral asymmetry was reduced from the pre- to the post-test in the NpL group only, which was due to a higher rate of improvement with the nonpreferred leg after the experimental training. These results are indicative of the role played by bilateral practice in modifying lateral asymmetries of performance established as a consequence of previous unilateral training.

Journal Article↗

PubMed2002

Lateral asymmetries in the development of the overarm throw.

Lateral asymmetries of manual, pedal, and ocular preferences, and motor asymmetry in the performance of the forceful overarm throw were analyzed in 71 children aged 4 to 10 years old. Performance with each side of the body was assessed on the basis of qualitative analysis, as proposed by M. A. Roberton and L. Halverson (1984) for identification of developmental stages by components of the task. Lateral preference was indicated by the frequency the children used the right or the left side of their body to carry out different manual, pedal, and ocular tasks. The overarm throw movement pattern was developed with both sides of the body but at different levels. Development of the nondominant side lagged behind that of the dominant side at all ages; a significant asymmetry in performance detected in the 4-year-olds was stable up to the age of 10 years. Indices of asymmetry for lateral preference and performance were found to be specific because no consistent correlations were observed among them throughout the age periods studied. Those results show the multidimensional character of human laterality and imply a property of motor development that prevents asymmetry of performance from increasing because of unilateral practice.

Arm↗