1,720,975 research outputs found
Familiarity modulates motor activation while other species' actions are observed: a magnetic stimulation study
No full textObserving other people's actions facilitates the observer's motor system as compared with observing the same individuals at rest. This motor activation is thought to result from mirror-like activity in fronto-parietal areas, which enhances the excitability of the primary motor cortex via cortico-cortical pathways. Although covert motor activation in response to observed actions has been widely investigated between conspecifics, how humans cope with other species' actions has received less attention. For example, it remains unclear whether the human motor system is activated by observing other species' actions, and whether prior familiarity with the non-conspecific agent modulates this activation. Here, we combined single-pulse transcranial magnetic stimulation and motor-evoked potential recording to explore the impact of familiarity on motor activation during the observation of non-conspecific actions. Videos displaying actions performed either by a conspecific (human) or by a non-conspecific (dog) were shown to individuals who had prior familiarity or no familiarity at all with the non-conspecific agent. We found that, whereas individuals with long-lasting familiarity showed similar levels of motor activation for human and canine actions, individuals who had no familiarity showed higher motor activation for human than for canine actions. These findings suggest that the human motor system is flexible enough to resonate with other species, and that familiarity plays a key role in tuning this ability
Contextual modulation of motor resonance during the observation of everyday actions
No full textNeuroimaging studies on action observation suggest that context plays a key role in coding high-level components of motor behavior, including the short-term and the end-goal of an action. However, little is known about the possible role of context in shaping lower-levels of action processing such as reading action kinematics and simulating muscular activity. Here, we combined single-pulse TMS and motor-evoked potentials (MEPs) recording to explore whether top-down contextual information is capable of modulating low-level motor representations. We recorded MEPs from FDI and FCR muscles while participants watched videos about everyday actions embedded in congruent, incongruent or ambiguous contexts. Videos were interrupted before action ending, and participants were requested to predict the course of the observed action. A contextual modulation of corticospinal excitability was observed only for the FDI muscle, which is specifically involved in the execution of reaching-to-grasping movements, and whose corticospinal pathway is influenced by the observation of the very same movements. This modulation was reflected in a selective decrease of corticospinal excitability during the observation of actions embedded in incongruent as compared to congruent and ambiguous contexts. These findings indicate that motor resonance is not an entirely automatic process, but it can be modulated by high-level contextual representations
Tracking the time course of top-down contextual effects on motor responses during action comprehension
No full textContext plays a key role in coding high-level components of others' behavior, including the goal and the intention of an observed action. However, little is known about its possible role in shaping lower levels of action processing, such as simulating action kinematics and muscular activity. Furthermore, there is no evidence regarding the time course and the neural mechanisms subserving this modulation. To address these issues, we combined single-pulse transcranial magnetic stimulation and motor-evoked potentials while healthy humans watched videos of everyday actions embedded in congruent, incongruent, or ambiguous contexts. Video endings were occluded from view and participants had to predict action unfolding. Transcranial magnetic stimulation was delivered at 80, 240, and 400 ms after action onset. An earlier selective facilitation of motor resonance occurring at 240 ms was observed for actions embedded in congruent contexts, compared with those occurring in incongruent and ambiguous ones. Later on, at 400 ms, a selective inhibition of motor resonance was found for actions embedded in incongruent contexts, compared with those taking place in congruent and ambiguous ones. No modulations were observed at 80 ms. Together, these findings indicate that motor resonance can be modulated by contextual information with different timings, depending on the (in)congruency between the different levels of action representation. Furthermore, the different time course of these effects suggests that they stem from partially independent mechanisms, with the early facilitation directly involving M1, and the later inhibition recruiting high-level structures outside the motor system
Contextualizing action observation in the predictive brain: Causal contributions of prefrontal and middle temporal areas
Full text linkContext facilitates the recognition of forthcoming actions by pointing to which intention is likely to drive them. This intention is thought to be estimated in a ventral pathway linking MTG with frontal regions and to further impact on the implementation of sensory predictions within the action observation network (AON). Additionally, when conflicting intentions are estimated from context, the DLPFC may bias action selection. However, direct evidence for the contribution of these areas to context-embedded action representations in the AON is still lacking. Here, we used a perturb-and-measure TMS-approach to disrupt neural activity, separately in MTG and DLPFC and subsequently measure cortico-spinal excitability while observing actions embedded in congruent, incongruent or ambiguous contexts. Context congruency was manipulated in terms of compatibility between observed kinematics and the action goal suggested by the ensemble of objects depicted in the environment. In the control session (vertex), we found an early facilitation and later inhibition for kinematics embedded in congruent and incongruent contexts, respectively. MTG stimulation altered the differential modulation of M1 response to congruent vs. incongruent contexts, suggesting this area specifies prior representations about appropriate object graspability. Interestingly, all effects were abolished after DLPFC stimulation highlighting its critical role in broader contextual modulation of the AON activity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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