Hand differences in aiming task: a complementary spatial approach and analysis ofdynamic brain networks with EEG.

Left and right-hand exhibit differences in the execution of movements. Particularly, it has been shown that manual goal-directed aiming is more accurate with the right hand than with the left, which has been explained through the shorter time spent by the right hand in the feedback phase (FB). This explanation makes sense for the temporal aspects of the task; however, there is a lack of explanations for the spatial aspects. The present study hypothesizes that the right hand is more associated with the FB, while the left hand is more strongly associated with the pre-programming phase (PP). In addition, the present study aims to investigate differences between hands in functional brain connectivity (FBC). We hypothesize an increase in FBC of the right hand compared to the left hand. Twenty-two participants performed 20 trials of the goal-directed aiming task with both hands. Overall, the results confirm the study's hypotheses. Although the right hand stopped far from the target at the PP, it exhibited a lower final position error than the left hand. These findings imply that during the FB, the right hand compensates for the higher error observed in the PP, using the visual feedback to approach the target more closely than the left hand. Conversely, the left hand displayed a lower error at the PP than the right. Also, the right hand displayed greater FBC within and between brain hemispheres. This heightened connectivity in the right hand might be associated with inhibitory mechanisms between hemispheres.

Motor learning and tDCS: A systematic review on the dependency of the stimulation effect on motor task characteristics or tDCS assembly specifications.

TDCS is one of the most commonly used methods among studies with transcranial electrical stimulation and motor skills learning. Differences between study results suggest that the effect of tDCS on motor learning is dependent on the motor task performed or on the tDCS assembly specification used in the learning process. This systematic review aimed to analyze the tDCS effect on motor learning and verify whether this effect is dependent on the task or tDCS assembly specifications. Searches were performed in PubMed, SciELO, LILACS, Web of Science, CINAHL, Scopus, SPORTDiscus, Cochrane Central Register of Controlled Trials (CENTRAL), Embase, and PsycINFO. Articles were included that analyzed the effect of tDCS on motor learning through pre-practice, post-practice, retention, and/or transfer tests (period ≥24 h). The tDCS was most frequently applied to the primary motor cortex (M1) or the cerebellar cortex (CC) and the majority of studies found significant stimulation effects. Studies that analyzed identical or similar motor tasks show divergent results for the tDCS effect, even when the assembly specifications are the same. The tDCS effect is not dependent on motor task characteristics or tDCS assembly specifications alone but is dependent on the interaction between these factors. This interaction occurs between uni and bimanual tasks with anodal uni and bihemispheric (bilateral) stimulations at M1 or with anodal unihemispheric stimulations (unilateral and centrally) at CC, and between tasks of greater or lesser difficulty with single or multiple tDCS sessions. Movement time seems to be more sensitive than errors to indicate the effects of tDCS on motor learning, and a sufficient amount of motor practice to reach the "learning plateau" also seems to determine the effect of tDCS on motor learning.

The Effect of Different Combinations of Practice Schedules on Motor Response Stability during Practice.

Many results in motor learning have indicated that relative and absolute timing dimensions are modulated by factors that modify response stability among trials. One of these factors is the combination of constant and variable practices. Although many researchers have investigated the combination of practice schedules, these researchers have used measurements that do not assess performance and motor response separately. This study aimed to investigate the effect of different combinations of practice schedules on motor response stability during practice. Participants performed a sequential key-pressing task with two goals: (1) to learn the relative timing dimension and (2) the absolute timing dimension. Participants were assigned to one of two groups: constant-variable or variable-constant. Our findings indicate an influence of the increase in variability over the practice in the constant-variable group. Precisely, the increase in variability of total time in the second half (constant-variable group) of practice was followed by the maintenance of the same level of cross-correlate between absolute timing error and variability of total time. Finally, our findings support the hypothesis that practicing in a constant schedule favors the relative timing dimension of learning regardless of the order in which the constant practice is provided.

Association Between Cross-Limb Transfer and Practice Organization.

Although the importance of practice has been evidenced in early studies of cross-limb transfer, the association between cross-limb transfer and practice organization remains unknown. The two primary means of organizing practice are constant practice (CP) and variable practice (VP). When the same generalized motor program governs the motor responses, VP produces better transfer than CP. Thus, we hypothesized that VP would generate a higher cross-limb transfer level than CP. We assigned 40 participants to CP or VP groups and conducted an experiment consisting of three phases: pre-test, practice, and transfer test. At pre-test, all participants practiced eight trials of a sequence key-pressing task with the non-dominant hand (NDH). After the pre-test, all participants performed a practice phase of 72 trials with the dominant hand, but CP and VP groups underwent their different practice schedules (CP or VP) such that the CP group practiced a sequence key-pressing task in one sequence, and the VP group practiced four different sequences randomly. On the transfer test all partcipants completed eight trials with the NDH 24 hours after the practice phase. The CP group showed better performance than the VP group on the transfer test, and we concluded that the effects of practice organization in cross-limb transfer are distinct from intra- and inter-task transfer such that the specificity of practice explained the benefits of CG.

O conhecimento do professor de educação física sobre aprendizagem motora / O conhecimento do professor de educação física sobre aprendizagem motora / El conocimiento del profesor de educación física sobre el aprendizaje motor

O objetivo deste estudo foi investigar o nível de conhecimento de graduados e graduandos em Educação Física sobre Aprendizagem Motora. Para isso, foi elaborado um questionário com 20 questões, sendo a primeira parte relacionada à identificação dos participantes e a segunda relacionada à Aprendizagem Motora. A análise foi feita com base na frequência de respostas dos participantes. A maioria dos participantes afirmou que sabiam o que era Aprendizagem Motora. No entanto, exibiram dificuldades em relação a algumas informações sobre a parte teórica. Além disso, os participantes apresentaram dificuldade em responder questões relacionadas aos fatores que influenciam a aprendizagem motora. Apesar do conhecimento sobre a temática contribuir efetivamente na forma pela qual o professor de educação física planeja e conduz as suas aulas, os participantes apresentaram impasses em responder às questões (AU).

The study aimed to investigate the level of knowledge of undergraduate and graduate students in physical education on Motor Learning. For this, a questionnaire with 20 questions was elaborated, the first part related to the identification of the participants and the second related to Motor Learning. The analysis was made based on the frequency of responses from the participants. Most of the participants stated that they knew what Motor Learning was. However, they showed difficulties about some information about the theoretical part. Also, the participants had difficulty in answering questions related to the factors that influence motor learning. Despite the knowledge about the theme effectively contributing to the way the physical education teacher plans and conducts his classes, the participants presented impasses in answering the questions (AU).

El objetivo del estudio fue investigar el nivel de conocimiento de estudiantes de pregrado y posgrado en educación física sobre el aprendizaje motor. Para esto, se elaboró un cuestionario con 20 preguntas, la primera parte relacionada con la identificación de los participantes y la segunda relacionada con el aprendizaje motor. El análisis se realizó en función de la frecuencia de las respuestas de los participantes. La mayoría de los participantes declararon que sabían lo que era el aprendizaje motor. Sin embargo, mostraron dificultades en relación con alguna información sobre la parte teórica. Además, los participantes tuvieron dificultades para responder preguntas relacionadas con los factores que influyen en el aprendizaje motor. A pesar de que el conocimiento sobre el tema contribuyó efectivamente a la forma en que el maestro de educación física planifica y dirige sus clases, los participantes presentaron dificultades para responder las preguntas (AU).

Mirror therapy in upper limb motor recovery and activities of daily living, and its neural correlates in stroke individuals: A systematic review and meta-analysis.

Available literature indicates that 30-66% of stroke survivors present persistent upper limb impairment. Considering the importance of upper limb function for activities of daily living, it is necessary to investigate neurorehabilitation therapies that could improve the upper limb function. Among stroke complementary therapies, mirror therapy has shown promising results. Thus, the aim of this systematic review and meta-analyses was to review and synthesize clinical evidence on the use of mirror therapy on motor recovery of the upper limb and activities of daily living, and its neural correlates in stroke patients. The literature search was carried out in PubMed, ISI Web of Science, and Scopus databases. Twenty-nine studies met all the inclusion criteria. Two meta-analyses were conducted to compare mirror therapy with sham therapy on two general measures, upper limb assessment and activities of daily living. Results suggest that mirror therapy was better than sham therapy, mainly in the subacute phase, but the meta-analyses were nonsignificant. In addition, mirror therapy and cortical reorganization showed potential neural correlates, such as the primary motor cortex, precuneus, and posterior cingulate cortex.

No Effects of Mental Fatigue and Cerebral Stimulation on Physical Performance of Master Swimmers.

Background: Mental fatigue is a psychobiological state caused by extended periods of cognitive effort, and evidence suggests that mentally fatigued athletes present impaired physical performance. Different ergogenic aids have been proposed to counteract the deleterious effects of mental fatigue, but whether brain stimulation can counteract mental fatigue is still unknown. This scenario is even more obscure considering the effects of these interventions (mental fatigue induction and brain stimulation) in a very experienced population consisting of master athletes. Method: Ten master swimmers (30 ± 6 years old and 14 ± 8 years of experience) participated in the study. They underwent four experimental conditions before an 800-m freestyle test: mental fatigue with brain stimulation; mental fatigue without brain stimulation; absence of mental fatigue with brain stimulation; and absence of mental fatigue and no brain stimulation. Mental fatigue was induced by a cognitively demanding Stroop Color Test, whereas stimulation was applied on the temporal cortex. After that, the athletes swan 800 m as fast as possible and provided their ratings of perceived exertion (RPE) every 200 m. Results: Mental fatigue was effectively induced, as evidenced by a greater fatigue perception and more errors in the last blocks of the cognitive task. Mental fatigue induction did not influence performance (time to complete the swimming trial) and RPE. Similarly, brain stimulation failed to change these two parameters, regardless of mental fatigue induction. Conclusion: The prolonged physical performance of experienced master athletes is not influenced, under the present conditions, by mental fatigue induction, cerebral stimulation, and their association.

Influence of Chronotype on Motor Behavior in Healthy Individuals: Analyses of Manual Dexterity in Different Times of the Day.

This study investigated the influence of chronotype on motor behavior in a manual dexterity task performed at different times of the day. Sixteen healthy adults of each chronotype (morning, evening, and neither), as measured by the Morningness-Eveningness Questionnaire, practiced both conditions of the Grooved Pegboard Test either in the morning or in the afternoon to early evening. The "neither" chronotype (65.12 ± 7.46) was outperformed (ps ≤ .03) by both the morning (56.09 ± 7.21) and evening (58.94 ± 7.53) chronotypes when the task had higher cognitive and motor demand but was not outperformed in the task with lower demand (morning = 18.46 ± 2.11; evening = 19.34 ± 2.79; neither = 21.47 ± 2.54; p > .05). No difference between the morning and evening chronotypes was found at the different times of the day (ps > .05), suggesting that a manual dexterity task is not sufficiently demanding to be influenced by chronotype.

The effect of context variability on motor learning.

Although the practice schedule and variation in incidental context have been investigated together, it is not clear whether just variation in incidental context can beneficiate motor learning. Therefore, the present study aimed to investigate the effect of context variability on motor learning. We hypothesized the practice in a variable incidental context would enable learners to be more resistant to the effects of the contextual changes when compared to a constant incidental context practice. Twenty-four participants were assigned to one of the two groups: constant incidental context (G_CC) or variable incidental context (G_VC). During practice, the G_CC practiced a sequence keypressing task in one color and a position showed on the computer screen. The G_VC practiced the same sequence in four different combinations of color and position. Twenty four hours, the same contexts practiced on practice (SAME) was performed and immediately after, a new sequential movement in new color and new position (SWITCH) was performed. The results indicated that the G_VC showed better performance than the G_CC on the SWITCH condition, mainly in measures related to planning/selection process. The results were explained by degree of similarity among processing events engaged during different moments and by development of a filter of information based on attentional selection.

TDCS of the Primary Motor Cortex: Learning the Absolute Dimension of a Complex Motor Task.

The primary motor cortex (M1) is one of the main cortical areas involved in motor learning. However, little is known about its differential role in the learning of the relative and absolute dimensions of motor skills. We investigated the role of M1 in the learning of the dimensions of a complex motor skill. Forty-eight participants practiced golf putting and were stimulated for 20 minutes with real or sham bihemispheric tDCS before acquisition. tDCS improved global performance from pre- to post-test. Only those with worse initial performance who were stimulated by tDCS showed a significant improvement in the skill's absolute dimension. No effects of tDCS were found for the relative dimension. Our results suggest that M1 has a distinct participation in the learning of the absolute dimension of complex motor skills, and tDCS effects are influenced by the learner's level of initial performance.

Mental practice is associated with learning the relative timing dimension of a task.

Learning about the relative timing dimension of a motor skill is enhanced by factors that promote higher response stability between trials. Conversely, learning the absolute timing dimension is favored by lower trial-to-trial stability. The mental practice may increase response stability during acquisition since there is a low possibility of adjustments made between trials. Thus, this study aimed to test the hypothesis that some factors that increase response stability during the acquisition phase contribute to an enhanced relative timing dimension learning. Our hypothesis is that mental practice shows less relative timing error than the absence of practice. A sequential key-pressing task was practiced with two goals: learn (1) relative timing dimension and (2) absolute timing dimension. Participants were assigned to one of three groups: Physical, Mental, or No practice. The Physical group showed greater learning of both dimensions than the other two groups. The Mental group showed greater learning of relative timing dimension than the No practice group. The results suggest that mental practice produces increased stability, which in turn promotes learning of the relative timing dimension.

Análise da Lateralidade e Destreza Manual em Crianças com Transtorno do Espectro Autista / Analysis of Laterality and Manual Dexterity in Children with Autistic Spectrum Disorder

RESUMO: Este estudo teve como objetivo analisar a lateralidade e a destreza manual em crianças com Transtorno do Espectro Autista (TEA). Do ponto de vista da motricidade humana, a lateralidade contribui para o processo de maturação motora. Figura-se entre as principais características do autismo o atraso nas habilidades motoras grossas e finas, com piora progressiva no quadro. Analisar o nível de lateralidade do indivíduo com TEA torna-se importante por possibilitar uma direção na intervenção motora com o intuito de melhorar a funcionalidade do autista e sua qualidade de vida. A amostra deste estudo foi composta por oito crianças, alunos de uma instituição de ensino pública, do sexo masculino, com idade média de 8,75±1,83 anos e diagnosticadas com TEA com base no DSM-V. Os resultados mostraram que os participantes do estudo parecem apresentar lateralidade destra e, também, melhor desempenho com a mão preferida em uma tarefa de destreza manual. Observou-se que, na tarefa que exigiu maior atenção e destreza, a diferença no desempenho das mãos foi significativa. Já na tarefa com menor demanda atencional e de destreza manual, o desempenho entre as mãos não foi significante, porém foi nesse momento que foram observados os maiores erros na execução. A motivação pode ser uma variável fundamental para o desempenho motor em tarefas que avaliam o tempo de execução. É importante uma maior ênfase no desenvolvimento da motricidade desses indivíduos durante a fase escolar para diminuir as dificuldades motoras e, consequentemente, melhorar a qualidade de vida, sensação de bem-estar, autonomia e interação social.

ABSTRACT: This study aimed to analyze laterality and manual dexterity in children with Autism Spectrum Disorder (ASD). From the point of view of human motor skills, laterality contributes to the motor maturation process. Among the main characteristics of autism is the delay in gross and fine motor skills, with progressive worsening in the condition. Analyzing the level of laterality of the individual with ASD becomes important because it allows a direction in the motor intervention in order to improve the functionality and quality of life of the autistic person. The sample of this study was composed of eight children, students of a public education institution, male, with an average age of 8.75 ± 1.83 years old and diagnosed with ASD based on the DSM-V. The results showed that the study participants seem to have right handedness and also better performance with the preferred hand in a manual dexterity task. It was observed that, in the task that demanded more attention and dexterity, the difference in hand performance was significant. In the task with the lowest attentional demand and manual dexterity, the performance between the hands was not significant; however, it was at that moment that the biggest mistakes in execution were observed. Motivation can be a fundamental variable for motor performance in tasks that assess execution time. It is important to emphasize the development of the motor skills of these individuals during the school phase to reduce motor difficulties and, consequently, improve quality of life, sense of well-being, autonomy and social interaction.

Motor learning and COMT Val158met polymorphism: Analyses of oculomotor behavior and corticocortical communication.

Differences in motor learning can be partially explained by differences in genotype. The catechol-O-methyltransferase (COMT) Val158Met polymorphism regulates the dopamine (DA) availability in the prefrontal cortex modulating motor learning and performance. Given the differences in tonic and phasic DA transmission, this study aimed to investigate whether the greater cognitive flexibility associated with the Val allele would favor the learning of movement parametrization, while the greater cognitive stability associated with the Met allele favors the acquisition of the movement pattern. Furthermore, we investigated if the genotypic characteristics impact visual scanning of information related to parametrization and to the movement pattern, and the level of cortical connectivity associated with motor planning and control. Performance and learning of a sequential motor task were compared among three genotypes (Val/Val, Val/Met, and Met/Met), as well as their oculomotor behavior and level of cortical coherence. The findings show that the cognitive flexibility promoted by the Val allele is associated with a better parametrization. The search for information through visual scanning was specific to each genotype. Also, a greater cortical connectivity associated with the Val allele was found. The combined study of behavioral, electrophysiological and molecular levels of analysis showed that the cognitive stability and flexibility associated with the COMT alleles, influence specific aspects of motor learning.

Focus of attention and online demonstration effects on temporal error and muscle activation / Efeitos do foco de atenção e demonstração online no erro temporal e na ativação muscular

Abstract The purpose of the present study was to examine whether there would be performance differences between external and internal focus of attention conditions and an online demonstration condition, and if these differences would be observed at a neuromuscular level through EMG analysis, in addition to traditional outcome measures. We hypothesized that under the demonstration condition participants would perform better than under external and internal focus conditions. We also hypothesized that demonstration condition would show smaller EMG activity than external and internal focus conditions. Furthermore, we hope to replicate the benefits of external focus in relation to internal focus, both in outcome and product measures. Six male participants performed a bilateral leg extension under internal focus of attention, external focus of attention and online demonstration conditions. Muscular contractions goal times were set for concentric muscle action (4 seconds) and eccentric muscle action (2 seconds). An electrogoniometer was used to record muscular activation (production measures), and temporal error was used to observe performance (outcome measures). Results showed that online demonstration condition obtained better performance than external focus condition and a reduced muscular activation. However, differences between internal focus and the other experimental conditions were not found. These findings advance in the understanding mechanisms underpining the focus of attention, such as proposed by Constrained Action Hypothesis.

Resumo O objetivo do presente estudo foi avaliar as diferenças no desempenho entre as condições de foco de atenção externo e interno e uma condição de demonstração online. Adicionalmente, se essas diferenças seriam observadas em um nível neuromuscular por meio da análise EMG, além das medidas de resultados tradicionais. Foi levantada a hipótese que sob a condição de demonstração os participantes teriam um desempenho melhor do que sob as condições de foco externo e interno. Também foi levantado a hipótese que a condição de demonstração apresentaria menor atividade EMG do que as condições de foco externo e interno. Além disso, esperava-se corrobora os benefícios do foco externo em relação ao foco interno, tanto nas medidas de resultado quanto de produto. Seis participantes do sexo masculino realizaram uma extensão de perna bilateral nas condições: foco de atenção interno, foco de atenção externo e condições de demonstração online. Os tempos de meta de contrações musculares foram definidos para ação muscular concêntrica (4 segundos) e ação muscular excêntrica (2 segundos). Um eletrogoniômetro foi usado para registrar a ativação muscular (medidas de produção) e o erro temporal foi usado para observar o desempenho (medidas de resultado). Os resultados mostraram que a condição de demonstração online obteve melhor desempenho do que a condição de foco externo e uma ativação muscular reduzida. No entanto, não foram encontradas diferenças entre o foco interno e as outras condições experimentais. Esses achados avançam no entendimento dos mecanismos que sustentam o foco de atenção, como o proposto pela Constrained Action Hypothesis.

Körperkoordinationstest Für Kinder (KTK) for Brazilian Children and Adolescents: Factor Analysis, Invariance and Factor Score.

The decrease in children motor competence, with a consequent reduction in the levels of physical activities and fitness, impacting health negatively, has affected children across countries. In addition to consistent intervention strategies, it is necessary to use appropriate instruments. The Körperkoordinationstest Für Kinder (KTK) is a reliable and low-cost motor coordination (MC) test used in several countries but lacking psychometric evidence in the Brazilian population. The present study investigates the factor structure of KTK in a Brazilian sample; and, compared four possibilities of calculating the factorial score of the test, precisely the sum of the scores, sum of the standard scores, weighted method, and the refined method. The participants of the study consisted of 565 volunteers (49.9% boys), from 5 to 10 (7.93 ± 1.51) years of age, with a body mass index (BMI) means of 17.04 (±2.81). The results showed that the KTK factor structure was adequate to the model for the total sample, by sex, and by age groups. However, the results did not confirm the invariance between sexes and age groups. Besides, our result showed that the sum of the raw scores of the subtests could be used as the factor score method in KTK. In the end, we conclude that the KTK is a valid test to measure the MC of Brazilian children and adolescents, with features that qualify it as a useful instrument both for research and for the practice.

Bi-hemispheric anodal transcranial direct current stimulation worsens taekwondo-related performance.

Transcranial Direct Current Stimulation (tDCS) is a neuromodulatory technique that has been used as an ergogenic aid in exercise/sports performance. However, little is known about its effects on highly-trained subjects, as athletes. The present study aimed to verify the effects of bi-hemispheric anodal tDCS (a-tDCS) on the performance of taekwondo athletes. Additionally, we investigated the persistence of the effects of the a-tDCS one hour after it. Nineteen Taekwondo athletes received active or sham bi-hemispheric a-tDCS over the primary motor cortex (M1). a-tDCS was delivered at 1.5 mA for 15 min. Athletes performed Countermovement Jumps (CMJ) and the Frequency Speed of Kick Test (FSKT) immediately (Mo1) and one hour after stimulation (Mo2). The athletes also reported their session-rating of perceived exertion (session-RPE). The total number of kicks (TK) was higher in sham than in the active a-tDCS condition (p < 0.01). In addition, TK was higher at Mo2 than at Mo1 (p < 0.05). Similarly, the session-RPE was higher in the a-tDCS condition (p < 0.05) and was greater one-hour post-stimulation (p < 0.01). No differences were found for CMJ performance (p > 0.05). Thus, bi-hemispheric a-tDCS worsens performance of taekwondo athletes, and the effect remains present even 1 h after the stimulation.

Oculomotor behavior and the level of repetition in motor practice: Effects on pupil dilation, eyeblinks and visual scanning.

The benefits of less repetitive practice in motor learning have been explained by the increased demand for memory processes during the execution of motor skills. Recently, a new perspective associating increased demand for perception with less repetitive practice has also been proposed. Augmented information gathering and visual scanning characterize this higher perceptual demand. To extend our knowledge about mental effort and perceptual differences in practice organization, the association between oculomotor behavior and type of practice was investigated. We required participants to press four keys with different absolute and relative timing goals during the acquisition phase. An eye-tracker captured visual scanning of the skill's absolute and relative information displayed on the screen. Participants were tested 24 h after acquisition by a retention and transfer test. A higher level of both pupil dilation and amount of eyeblinks indicated an increased mental effort in less repetitive practice compared to more repetitive practice. Visual scanning of the skill's relative and absolute information was specific to the type of practice. The findings indicate many differences in oculomotor behavior associated with the practice schedule.

Association between the catechol-O-methyltransferase (COMT) Val158Met polymorphism and motor behavior in healthy adults: A study review.

The influence of individual differences in cognition and behavior may be partly explained by the different genetic polymorphisms. Among the genetic polymorphisms capable of altering cognitive and behavioral functions, the catechol-O-methyltransferase (COMT) Val158Met polymorphism regulates the availability of dopamine (DA) in the prefrontal cortex and has a trimodal distribution in the population. The Met allele has higher DA availability in the synaptic clefts and can be associated with cognitive stability. Val homozygous individuals exhibit lower DA concentrations in the synaptic clefts, which can be associated with cognitive flexibility. Heterozygotes have intermediate DA concentrations in the synaptic clefts. In the perspective of motor behavior, greater cognitive stability would be advantageous when the practice requires maintenance and refinement of a movement pattern, while a greater cognitive flexibility would be fundamental for practices demanding motor adaptation caused by disturbances. Thus, this integrative review aimed to analyze, in healthy populations, possible associations between the COMT polymorphism and motor behavior, as well as to investigate whether the effects of the COMT genotypes from the perspective of the roles played by tonic and phasic DA are associated with the stability/flexibility required by the nature of the motor task. The search for the articles was carried out in the PubMed, ISI Web of Science and Scopus databases. Six studies that met all the requirements specified in the inclusion criteria were selected. Results suggest an association between COMT polymorphism and motor behavior. Conflicting results regarding the effects of the different COMT polymorphisms on adaptation and sequential motor tasks were found, as well as on the roles played by tonic and phasic DA. Despite the inconsistencies encountered, it was possible to identify that the different COMT genotypes lead to different effects in relation to the nature of the practiced motor task. Due to the reduced number of articles investigating the association between COMT polymorphism and motor behavior, relevant questions about this relation remain under-investigated.

Cathodal tDCS of the Left Posterior Parietal Cortex Increases Proprioceptive Drift.

In aiming movements the limb position drifts away from the defined target after some trials without visual feedback, a phenomenon defined as proprioceptive drift (PD). There are no studies investigating the association between the posterior parietal cortex (PPC) and PD in aiming movements. Therefore, cathodal and sham transcranial direct current stimulation (tDCS) were applied to the left PPC concomitantly with the performance of movements with or without vision. Cathodal tDCS applied without vision produced a higher level of PD and higher rates of drift accumulation while it decreased peak velocity and maintained the number of error corrections, not affecting movement amplitude. The proprioceptive information seems to produce an effective reference to movement, but with PPC stimulation it causes a negative impact on position.

Análise da assimetria de força de preensão manual entre os sexos / Analysis of the asymmetry of hand gripping force between the sexes

É da natureza dos seres humanos apresentarem preferências na realização de tarefas do dia-a-dia. Esta preferência está associada à lateralidade. Um dos campos de estudo sobre a lateralidade é a assimetria lateral, que está presente tanto na dimensão da preferência quanto no desempenho. Objetivo: Este estudo teve como objetivo comparar a assimetria de força de preensão manual entre os sexos, e identificar se há associação entre assimetria de desempenho e assimetria de preferência. Método: A amostra foi composta por 50 estudantes universitários que realizaram teste de força de preensão manual máxima. Resultados: Os resultados indicaram que o os homens apresentaram valores absolutos maiores, maior índice de assimetria e menor consistência quando comparados às mulheres. Além disso, a mão preferida apresentou valores maiores de força em ambos os sexos. Conclusão: Em linhas gerais, sugere-se que fatores genéticos, sociais, culturais e sexo influenciam o comportamento motor dos indivíduos e, consequentemente, as assimetrias de desempenho.

It is of the nature of human beings to have preferences to performing daily tasks. This preference is associated with the laterality. One of the fields of the laterality study is lateral asymmetry, that is present in both preference and performance dimensions. Aim: This study aimed to compare manual grip strength asymmetry between genders and to identify if there is an association between asymmetry of performance and preference asymmetry. Method: The sample consisted of 50 university students who performed maximum manual grip strength tests. Results: The results indicated that the men had higher absolute values, higher Asymmetry Index and lower consistency when compared to the women. In addition, the preferred hand presented higher strength values in both sexes. Conclusion: In general, it is suggested that genetic, social, cultural and gender factors influence the motor behavior of the individuals and consequently the appearance of the lateral asymmetries.