Interlateral asymmetry in the execution of a motor response

Gisele Braga Pinheiro
Departamento de Fisiologia e Biof?sica - Universidade de S

*Luiz Eduardo Ribeiro do Valle
Departamento de Fisiologia e Biof?sica - Universidade de S?o Paulo

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     Last modified: March 16, 2007

Abstract
Introduction and Objective: There are some evidences in the literature about the dominance of the left hemisphere in motor control. In this study, a search was realized to investigate if this dominance can exercise influence in a preparation of a response of finger?s movement. It was used a simple reaction time task (SRT), that can include a prior preparation, and a choice reaction time task (CRT) where this preparation is not possible because the response is directly related when the target appears.
Material and Methods: 12 young women took part of each experiment. The task consisted in press one key as fast as it is possible when a disc appeared. This disc surged from the left or from the right side of a fixed central point. The response would be 1, 2, 3 or 4 movements in agreement with the trial blocks, in a way to provide an increase in the motor difficulty. In the SRT, the volunteers should answer with the right hand in four trail blocks and with the left hand in another four blocks. In the CRT they should answer with the hand correspondent to the side where the target appeared. An auditive stimulus became 200ms before the main, approximately in half of the attempt in each block. This auditive stimulus was during 50 ms and the target 100 ms.
Results and Discussion: The reaction time did not vary in a significantly way in both tasks. In the SRT task, the time about submovements and pauses was longer in the left hand than in the right (p<0,04), except in the last submovement and the last pause of the response of 4 submovements. In the CRT task, the first pause time was longer to the left hand than the right (p<0,001). However, it was not found interlateral asymmetry for other submovements and pause time.
Conclusions: There are more efficient responses with the right hand than the left hand, especially in SRT task. This suggests that the left hemisphere is more competent than the right to prepare a manual motor response.
Financial support: FINEP,CAPES,CNPq.