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.

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.

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.

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.

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.

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.

The relative age effect on brazilian elite volleyball / O efeito da idade relativa no voleibol brasileiro de elite

ABSTRACT The relative age effect (RAE) refers to the advantage of the athletes born on the first months of the sport selection period compared to those born months later during such a selection process, which tends to favor athletes who are in a more developed maturational stage or those who have more advanced physical development compared to their younger counterparts born in the same year. This advantage occurs mainly in sport whose physical characteristics are determinant for obtaining success, such as volleyball, which leads to the premature exclusion or dropout of potential talents from sport. This study aims at assessing the RAE presence in Brazilian men's and women's elite volleyball by analysing the number of athletes who were born in each trimester of the year and had been ranked to the main national Super Leagues. The results showed no effect related to the RAE in Brazilian women's elite volleyball, whereas there was a higher representation of male athletes born in the first trimester compared to the ones born on the 3rd and 4th trimesters. These results point to a need for better understanding the causes and consequences of RAE in Brazilian men's volleyball in order to avoid premature exclusion or dropout of potential talents, thus, enabling an even greater development of this sport in the country.

RESUMO O efeito da idade relativa (EIR) refere-se à vantagem de atletas nascidos nos primeiros meses do período de seleção em relação a seus pares nascidos em meses posteriores no processo de seleção esportivo, que tende a favorecer atletas que encontram-se em estágio maturacional ou de desenvolvimento físico mais avançados que o de seus colegas mais jovens nascidos no mesmo ano. Esse favorecimento ocorre principalmente em esportes cuja característica física é determinante para se obter sucesso, como o voleibol, acarretando na exclusão ou abandono prematuro da modalidade por parte de talentos em potencial. O objetivo do estudo foi avaliar a presença do EIR no voleibol brasileiro de elite feminino e masculino, pela análise da distribuição do número de atletas rankeados para as Superligas masculina e feminina nascidos em cada trimestres do ano. Os resultados indicaram não haver EIR no voleibol feminino brasileiro de elite, enquanto no masculino há uma maior representação de atletas nascidos no primeiro trimestre em comparação àqueles nascidos nos 3º e 4º trimestres. Esses resultados apontam para a necessidade de se entender melhor as causas e consequências do EIR no voleibol masculino brasileiro, afim de evitar a exclusão ou abandono precoce do esporte de possíveis talentos, permitindo um maior desenvolvimento da modalidade no país.