BackgroundHuntington's disease (HD) is a fatal inherited neurodegenerative disease, caused by a

Huntington disease is a neurodegenerative disorder that involves preferential atrophy in the striatal complex and related subcortical nuclei. In this paper, which is based on a dataset extracted from the PREDICT-HD study, we use statistical shape analysis with deformation markers obtained through Large Deformation Diffeomorphic Metric Mapping of cortical surfaces to highlight specific atrophy patterns in the caudate, putamen, and globus pallidus, at different prodromal stages of the disease. Based on the relation to cortico-basal-ganglia circuitry, we propose that statistical shape analysis, along with other structural and functional imaging studies, may help expand our understanding of the brain circuitry affected and other aspects of the neurobiology of HD, and also guide the most effective strategies for intervention.

Parkinson's disease (PD) is a neurodegenerative disease causing both sensorimotor and non-motor impairments, and there is a clear need for non-medical approaches to improve quality of life. Dance is an increasingly popular activity among people with PD, which demonstrates potential therapeutic benefits. However, findings to date have been inconsistent, and little is known about the mechanisms underlying benefits of dance in PD. In this review, we provide an overview of research into dance for people with PD. The majority of evidence is in the sensorimotor domain, but cognitive, psychological and social effects have also been reported. We consider the role of cognitive representations of action within dance through observation, imitation and imagery, which may contribute to both sensorimotor and nonmotor outcomes for people with PD. Moreover, we discuss how these processes may be enhanced through dance to provide further benefits in everyday life. Finally, we propose avenues for future research to increase understanding of action representation in dance for PD, which has the potential to inform practice and maximize benefits.

Background: Action observation (AO) activates the motor system, influencing movement and increasing learning, and has been shown to improve speed and timing of movement in people with Parkinson's disease (PD). Importantly, however, effects on movement amplitude have not been quantitatively demonstrated. Additionally, motor imagery (MI) can increase behavioural and neural effects of AO, but the combined effects of AO+MI have never previously been explored in PD. The aim of this study was to investigate imitation of hand movement amplitude in people with PD following (i) AO and (ii) combined AO+MI. Methods: Twenty-four participants with mild to moderate PD and 24 healthy older adults observed and imitated videos showing a human hand moving between horizontal positions. Kinematics were recorded and modulation of vertical amplitude when replicating elevated vs. direct movements provided an index of imitation. After an initial set of AO trials, participants were instructed to engage in MI during observation for the remaining trials (AO+MI), emphasizing kinaesthetic (sensory) imagery. Results: Movement amplitude was imitated (modulated) for elevated vs. direct stimuli by both groups, and this imitation increased following MI instructions. Conclusions: These results demonstrate quantitatively for the first time that people with PD are able to modulate the amplitude of their hand movements following action observation, and that combining AO and MI increases imitation in PD. The effects parallel findings in healthy young participants, and indicate that combined action observation and motor imagery could be a promising therapeutic approach for PD. To indicate compliance with the preceding declaration and that you have obtained agreement from all of the authors of this paper to declare their compliance as well, please place an x here: _X__