Aprendizagem motora: o papel do córtex motor primário

Abstract

Behavioral studies have shown a more effective role of the less repetitive practice in the learning of the absolute dimension of the skill compared to the relative dimension. Neurobiological studies have pointed out to an association of the primary motor cortex (M1) with the organization of the specific movement elements. Although these studies did not use specific tasks to measure the learning of the absolute dimension of The skill, these studies have observed that force, direction and amplitude are elements organized by M1. Therefore, the aim of the study is to evaluate the role of M1 in the motor learning, ans the hypothesis is that M1 is more associated with the learning of the absolute dimension of the skill. Forty-eight participants were divided into 3 groups of practice (n = 16): constant practice group with transcranial direct current stimulation TDCs (CPG-TDCs), constant practice group sham (CPG-S) and random practice group (RPG). The GPC-TDCs received electrical stimulation (1mA) over M1 for 20 minutes before practice. The group CPC-S received only 36 seconds of stimulation and GRP did not receive stimulation. In the acquisition phase, participants performed 120 trials of a sequence typing on the numeric keyboard with absolute criterions time of 700, 900 and 1,100 ms and relative criterions time among keys (22,2% from 2 to 8, 44% from 8 to 6 and 33.3% from 6 to 4). The retention and transfer tests were performed 24 hours after acquisition phase, each test consisting of 12 trials. The transfer test was performed with an absolute criterion time of 1,300ms. In the retention test, the results did not show significant difference among groups in both the relative error measure (ER) and the absolute error (EA). In transfer test, significant difference was not found in ER. However, the CPG-TDCs presented lower level of error compared to the RPG in the EA measure. Therefore, the hypothesis that the M1 would be more associated with the absolute dimension than the relative dimension was confirmed in the present study. The modifications promoted by TDCs in the motor learning mechanisms seem to be more effective than changes generated by random practice in the parameterization of movement.