Familiarity modulates motor activation while other species' actions are observed: a magnetic stimulation study

A study of action difference on motor imagery based on delayed matching posture task

Objective. Motor imagery (MI)-based brain-computer interfaces (BCIs) provide an additional control pathway for people by decoding the intention of action imagination. The way people imagine greatly affects MI-BCI performance. Action itself is one of the factors that influence the way people imagine. Whether the different actions cause a difference in the MI performance is unknown. What is more important is how to manifest this action difference in the process of imagery, which has the potential to guide people to use their individualized actions to imagine more effectively.Approach.To explore action differences, this study proposes a novel paradigm named as action observation based delayed matching posture task. Ten subjects are required to observe, memorize, match, and imagine three types of actions (cutting, grasping and writing) given by visual images or videos, to accomplish the phases of encoding, retrieval and reinforcement of MI. Event-related potential (ERP), MI features, and classification accuracy of the left or the right hand are used to evaluate the effect of the action difference on the MI difference.Main results.Action differences cause different feature distributions, resulting in that the accuracy with high event-related (de)synchronization (ERD/ERS) is 27.75% higher than the ones with low ERD/ERS (p< 0.05), which indicates that the action difference has impact on the MI difference and the BCI performance. In addition, significant differences in the ERP amplitudes exists among the three actions: the amplitude of P300-N200 potential reaches 9.28μV of grasping, 5.64μV and 5.25μV higher than the cutting and the writing, respectively (p< 0.05).Significance.The ERP amplitudes derived from the supplementary motor area shows positive correlation to the MI classification accuracy, implying that the ERP might be an index of the MI performance when the people is faced with action selection. This study demonstrates that the MI difference is related to the action difference, and can be manifested by the ERP, which is important for improving MI training by selecting suitable action; the relationship between the ERP and the MI provides a novel index to find the suitable action to set up an individualized BCI and improve the performance further.

What modulates the Mirror Neuron System during action observation?: Multiple factors involving the action, the actor, the observer, the relationship between actor and observer, and the context

Seeing an agent perform an action typically triggers a motor simulation of that action in the observer's Mirror Neuron System (MNS). Over the past few years, it has become increasingly clear that during action observation the patterns and strengths of responses in the MNS are modulated by multiple factors. The first aim of this paper is therefore to provide the most comprehensive survey to date of these factors. To that end, 22 distinct factors are described, broken down into the following sets: six involving the action; two involving the actor; nine involving the observer; four involving the relationship between actor and observer; and one involving the context. The second aim is to consider the implications of these findings for four prominent theoretical models of the MNS: the Direct Matching Model; the Predictive Coding Model; the Value-Driven Model; and the Associative Model. These assessments suggest that although each model is supported by a wide range of findings, each one is also challenged by other findings and relatively unaffected by still others. Hence, there is now a pressing need for a richer, more inclusive model that is better able to account for all of the modulatory factors that have been identified so far.

Proactive gaze is present during biological and non-biological motion observation

Others' action observation activates in the observer a coordinated hand-eye motor program, covert for the hand (i.e. motor resonance), and overt for the eye (i.e. proactive gaze), similar to that of the observed agent. The biological motion hypothesis of action anticipation claims that proactive gaze occurs only in the presence of biological motion, and that kinematic information is sufficient to determine the anticipation process. The results of the present study did not support the biological motion hypothesis of action anticipation. Specifically, proactive gaze was present during observation of both a biological accelerated-decelerated motion and a non-biological constant velocity motion (Experiment 1), in the presence of a barrier able to restrict differences between the two kinematics to the motion profile of individual markers prior to contact (Experiment 2), but only if an object was present at the end point of the movement trajectory (Experiment 3). Furthermore, proactive gaze was found independently of the presence of end effects temporally congruent with the instant in which the movement stopped (Experiments 4, and 5). We propose that the involvement of the observer's motor system is not restricted to when the agent moves with natural kinematics, and it is mandatory whenever the presence of an agent or a goal is evident, regardless of physical appearance, natural kinematics, and the possibility to identify the action behind the stimulus.

Does watching Han Solo or C-3PO similarly influence our language processing?

Several studies have demonstrated that perceiving an action influences the subsequent processing of action verbs. However, which characteristics of the perceived action are truly determinant to enable this influence is still unknown. The current study investigated the role of the agent executing an action in this action-language relationship. Participants performed a semantic decision task after seeing a video of a human or a robot performing an action. The results of the first study showed that perceiving a human being executing an action as well as perceiving a robot facilitate subsequent language processing, suggesting that the humanness (The term "humanness" is used as meaning "belonging to human race" and not to refer to a personal quality) of the agent is not crucial in the link between action and language. However, this experiment was conducted with Japanese people who are very familiar with robots; thus, an alternative explanation could be that it is the unfamiliarity with the agent that could perturb the action-language relationship. To assess this hypothesis, we carried out two additional experiments with French participants. The results of the second study showed that, unlike the observation of a human agent, the observation of a robot did not influence language processing. Finally, the results of the third study showed that, after a familiarization phase, French participants too were influenced by the observation of a robot. Overall, the outcomes of these studies indicate that, more than the humanness of the agent, it is the familiarity which we have with this agent that is crucial in the action-language relationship.