During the rubber hand illusion (RHI), subjects experience an artificial hand as part of their own body, while the real hand is subject to a sort of 'disembodiment'. Can this altered belief about the body also affect physiological mechanisms involved in body-ownership, such as motor control? Here we ask whether the excitability of the motor pathways to the real (disembodied) hand are affected by the illusion. Our results show that the amplitude of the motor-evoked potentials recorded from the real hand is significantly reduced, with respect to baseline, when subjects in the synchronous (but not in the asynchronous) condition experience the fake hand as their own. This finding contributes to the theoretical understanding of the relationship between body-ownership and motor system, and provides the first physiological evidence that a significant drop in motor excitability in M1 hand circuits accompanies the disembodiment of the real hand during the RHI experience.DOI:
http://dx.doi.org/10.7554/eLife.14972.001
a b s t r a c tWhat enables individuals to act together? Recent discoveries suggest that a variety of mechanisms are involved. But something fundamental is yet to be investigated. In joint action, agents represent a collective goal, or so it is often assumed. But how, if at all, are collective goals represented in joint action and how do such representations impact performance? To investigate this question we adapted a bimanual paradigm, the circle-line drawing paradigm, to contrast two agents acting in parallel with two agents performing a joint action. Participants were required to draw lines or circles while observing circles or lines being drawn. The findings indicate that interpersonal motor coupling may occur in joint but not parallel action. This suggests that participants in joint actions can represent collective goals motorically.
Autism spectrum conditions (ASC) are characterized by social-communicative and motor coordination difficulties but in many cases also by an impaired capability to imagine movements. In this study we found that while two handed coordination in ASC can be developed as well as in typically developed persons, the development of motor imagery could still be immature in ASC, leading to difficulties in imagining, understanding as well as programming and coordinating complex movements.
IntroductionPhysical activity has been included in the list of twelve modifiable risk factors for dementia, despite conflicting results from observational and controlled studies. In particular it is not clear whether physical inactivity near the time of dementia diagnosis is a consequence or cause of dementia. We review all available studies reporting the possible association between having engaged in PA before 60 years of age and the risk of dementia.
Evidence acquisitionWe performed a systematic review based on the methodology reported in the Cochrane handbook for systematic reviews and following the PRISMA statement. Bibliographic searches were carried out on the databases PubMed, ISI Web of Science and the Cochrane Database of Systematic Reviews. Further references were retrieved from published systematic reviews on the same topic.Included studies were assessed using the Newcastle Ottawa scale.
Evidence synthesisThe bibliographic search yielded 1381 records. A total of 11 studies were included. Three of the included studies were case control studies, while the remaining 8 were cohort studies The overall quality of included studies was high. However, clinical criteria for the diagnosis of dementia, criteria to define and measure and PA and time-reference of exposure were heterogeneous, with some studies considering specific age range of exposure, and other reports dealing with more generic "adult age".
ConclusionsThis review suggests that there is insufficient evidence to conclude whether PA in early life may affect the incidence of dementia in later life. Studies in this field are very complicated and recognizing the impact of PA in early life given all the confounding factors is very difficult. Further studies are warranted. In these studies, it will be crucial to define the type, quantity and intensity of PA as well as to stratify analysis by sex, cultures and social classes.
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