Inter-limb coupling during diadochokinesis in Parkinson's and Huntington's disease

The power of multivariate approach in identifying EEG correlates of interlimb coupling

Interlimb coupling refers to the interaction between movements of one limb and movements of other limbs. Understanding mechanisms underlying this effect is important to real life because it reflects the level of interdependence between the limbs that plays a role in daily activities including tool use, cooking, or playing musical instruments. Interlimb coupling involves multiple brain regions working together, including coordination of neural activity in sensory and motor regions across the two hemispheres. Traditional neuroscience research took a univariate approach to identify neural features that correspond to behavioural coupling measures. Yet, this approach reduces the complexity of the neural activity during interlimb tasks to one value. In this brief research report, we argue that identifying neural correlates of interlimb coupling would benefit from a multivariate approach in which full patterns from multiple sources are used to predict behavioural coupling. We demonstrate the feasibility of this approach in an exploratory EEG study where participants (n = 10) completed 240 trials of a well-established drawing paradigm that involves interlimb coupling. Using artificial neural network (ANN), we show that multivariate representation of the EEG signal significantly captures the interlimb coupling during bimanual drawing whereas univariate analyses failed to identify such correlates. Our findings demonstrate that analysing distributed patterns of multiple EEG channels is more sensitive than single-value techniques in uncovering subtle differences between multiple neural signals. Using such techniques can improve identification of neural correlates of complex motor behaviours.

Relationship between motor coordination and executive function in adults and older adults

ABSTRACT Brazilian older adults present a relatively low schooling level when compared with other populations. In clinical practice, defining if more subtle alterations observed in executive function (EF) and motor coordination tests in older adults are due to an initial neurological condition or low schooling level is difficult. This study aimed to evaluate the possible differences in motor coordination and EF between adults and older adults with high and low schooling level as well as the possible correlations between motor coordination and EF in this sample. A total of 75 healthy individuals (aged from 30 to 89 years) were evaluated. EF was assessed by the trail making test (TMT) whereas motor coordination was assessed by the upper limb diadochokinetic test, which is the rapid alternation between supination and pronation of the forearms (right, left, both performing in-phase movements, and both performing anti-phase movements). Analysis of variance showed that age and schooling level possibly influenced EF and motor coordination. Possible relationships between EF and diadochokinesis were calculated by Pearson’s correlation. Older adults with low schooling level were significantly slower on the TMT part B (cognitive and motor) and delta TMT (cognitive). All groups were slower performing the anti-phase movement, especially those with low schooling level. Results showed only weak correlations between EF and motor coordination. Age and schooling level influenced executive function and motor coordination. However, the EF and motor coordination tests presented no correlation when these two factors were statistically corrected.

Relação entre a coordenação motora e a função executiva em adultos e idosos

RESUMO A população idosa brasileira possui escolaridade relativamente baixa, quando comparada a outras populações. Na prática clínica, torna-se difícil decidir se alterações mais sutis, observadas nos testes de função executiva (FE) e coordenação motora de idosos, devem-se a um quadro neurológico inicial ou à baixa escolaridade. O objetivo do trabalho foi investigar: (1) possíveis diferenças na coordenação motora e FE de adultos e idosos com escolaridade alta e baixa; e (2) possíveis correlações entre coordenação motora e FE nessa amostra. Foram avaliados 75 indivíduos saudáveis, com idade entre 30 e 89 anos. A FE foi avaliada por meio do trail making test (TMT) e a coordenação motora foi avaliada com o teste de diadococinesia dos membros superiores, que consiste na alternância rápida entre supinação e pronação do antebraço (direito, esquerdo, de ambos os antebraços em fase, e ambos em antifase). A análise de variância investigou possíveis influências da idade e da escolaridade na FE e coordenação motora. O teste de correlação de Pearson investigou possíveis relações entre FE e diadococinesia. Idosos com escolaridade baixa foram significativamente mais lentos na parte B (cognitivo-motora) e no delta (cognitiva) do TMT. Todos os grupos foram mais lentos na condição antifase, sobretudo os idosos com escolaridade baixa. Encontramos apenas correlações fracas entre FE e coordenação motora. A idade e a escolaridade influenciaram na FE e na coordenação motora; porém, os testes de FE e coordenação motora não apresentaram correlação quando esses dois fatores foram corrigidos estatisticamente.

Mechanomyography and acceleration show interlimb asymmetries in Parkinson patients without tremor compared to controls during a unilateral motor task

The mechanical muscular oscillations are rarely the objective of investigations regarding the identification of a biomarker for Parkinson's disease (PD). Therefore, the aim of this study was to investigate whether or not this specific motor output differs between PD patients and controls. The novelty is that patients without tremor are investigated performing a unilateral isometric motor task. The force of armflexors and the forearm acceleration (ACC) were recorded as well as the mechanomyography of the biceps brachii (MMGbi), brachioradialis (MMGbra) and pectoralis major (MMGpect) muscles using a piezoelectric-sensor-based system during a unilateral motor task at 70% of the MVIC. The frequency, a power-frequency-ratio, the amplitude variation, the slope of amplitudes and their interlimb asymmetries were analysed. The results indicate that the oscillatory behavior of muscular output in PD without tremor deviates from controls in some parameters: Significant differences appeared for the power-frequency-ratio (p = 0.001, r = 0.43) and for the amplitude variation (p = 0.003, r = 0.34) of MMGpect. The interlimb asymmetries differed significantly concerning the power-frequency-ratio of MMGbi (p = 0.013, r = 0.42) and MMGbra (p = 0.048, r = 0.39) as well as regarding the mean frequency (p = 0.004, r = 0.48) and amplitude variation of MMGpect (p = 0.033, r = 0.37). The mean (M) and variation coefficient (CV) of slope of ACC differed significantly (M: p = 0.022, r = 0.33; CV: p = 0.004, r = 0.43). All other parameters showed no significant differences between PD and controls. It remains open, if this altered mechanical muscular output is reproducible and specific for PD.

Targeting Gpr52 lowers mutant HTT levels and rescues Huntington's disease-associated phenotypes

See Huang and Gitler (doi:10.1093/brain/awy112) for a scientific commentary on this article.

Lowering the levels of disease-causing proteins is an attractive treatment strategy for neurodegenerative disorders, among which Huntington’s disease is an appealing disease for testing this strategy because of its monogenetic nature. Huntington’s disease is mainly caused by cytotoxicity of the mutant HTT protein with an expanded polyglutamine repeat tract. Lowering the soluble mutant HTT may reduce its downstream toxicity and provide potential treatment for Huntington’s disease. This is hard to achieve by small-molecule compound drugs because of a lack of effective targets. Here we demonstrate Gpr52, an orphan G protein-coupled receptor, as a potential Huntington’s disease drug target. Knocking-out Gpr52 significantly reduces mutant HTT levels in the striatum and rescues Huntington’s disease-associated behavioural phenotypes in a knock-in Huntington’s disease mouse model expressing endogenous mutant Htt. Importantly, a novel Gpr52 antagonist E7 reduces mutant HTT levels and rescues Huntington’s disease-associated phenotypes in cellular and mouse models. Our study provides an entry point for Huntington’s disease drug discovery by targeting Gpr52.

Avaliação interdisciplinar da diadococinesia: um estudo piloto

RESUMO Diadococinesia é a capacidade de executar movimentos rápidos, repetidos e alternados. Testes de diadococinesia podem avaliar tanto a fala quanto os membros superiores. O objetivo primário foi apresentar um protocolo interdisciplinar de avaliação da diadococinesia. Os objetivos secundários foram comparar o desempenho com os diferentes fonemas do teste de diadococinesia oral (/papapa/, /tatata/, /kakaka/ e /pataka/), comparar o desempenho com as diferentes condições do teste de diadococinesia de membros superiores (realizado com ambos os membros superiores de forma espelhada, apenas com o membro superior direito, apenas com o membro superior esquerdo, com ambos os membros superiores de forma alternada) e investigar possíveis relações entre diadococinesia oral e de membros superiores. Participaram quinze adultos/idosos saudáveis de 40 a 70 anos. Os dados foram representados por estatística descritiva. Os números de sílabas nas condições /papapa/, /tatata/, /kakaka/ e /pataka/ e os números de movimentos nas condições espelhado, direito, esquerdo e alternado foram comparados por ANOVA e correlacionados pelo teste de Pearson. Não houve diferença significativa nos resultados entre os fonemas do teste de diadococinesia oral (p<0,001). Houve diferença entre as condições avaliadas no teste de diadococinesia dos membros superiores (p<0,001). O número de fonemas repetidos esteve correlacionado com o desempenho alternado de membros superiores. Concluiu-se que a correlação entre os escores dos testes de diadococinesia oral e de membros superiores pode ser explicada pelo fato de a programação motora e a linguagem estarem predominantemente representadas no hemisfério esquerdo. Áreas cerebrais comuns/conectadas ou programas motores em comum podem nortear essas tarefas.

Suppression of MAPK11 or HIPK3 reduces mutant Huntingtin levels in Huntington's disease models

Most neurodegenerative disorders are associated with accumulation of disease-relevant proteins. Among them, Huntington disease (HD) is of particular interest because of its monogenetic nature. HD is mainly caused by cytotoxicity of the defective protein encoded by the mutant Huntingtin gene (HTT). Thus, lowering mutant HTT protein (mHTT) levels would be a promising treatment strategy for HD. Here we report two kinases HIPK3 and MAPK11 as positive modulators of mHTT levels both in cells and in vivo. Both kinases regulate mHTT via their kinase activities, suggesting that inhibiting these kinases may have therapeutic values. Interestingly, their effects on HTT levels are mHTT-dependent, providing a feedback mechanism in which mHTT enhances its own level thus contributing to mHTT accumulation and disease progression. Importantly, knockout of MAPK11 significantly rescues disease-relevant behavioral phenotypes in a knockin HD mouse model. Collectively, our data reveal new therapeutic entry points for HD and target-discovery approaches for similar diseases.

A more precise, repeatable and diagnostic alternative to surface electromyography - an appraisal of the clinical utility of acoustic myography

Acoustic myography (AMG) enables a detailed and accurate measurement of those muscles involved in a particular movement and is independent of electrical signals between the nerve and muscle, measuring solely muscle contractions, unlike surface electromyography (sEMG). With modern amplifiers and digital sound recording systems, measurements during physical activity both inside and outside a laboratory setting are now possible and accurate. Muscle sound gives a representation of the work of each muscle group during a complex movement, and under certain forms of movement even reveals both concentric and eccentric activity, something that sEMG is incapable of. Recent findings suggest that AMG has a number of advantages over sEMG, being simple to use, accurate and repeatable as well as being intuitive to interpret. The AMG signal comprises three physiological parameters, namely efficiency/coordination (E-score), spatial summation (S-score) and temporal summation (T-score). It is concluded that modern AMG units have the potential to accurately assess patients with neuromuscular and musculoskeletal complaints in hospital clinics, home monitoring situations as well as sports settings.