Shunsuke Hamasaki

Prediction of human's movement for collision avoidance of mobile robot

In order to operate mobile robot that can coexist with human, it is necessary to strike a balance between safety and efficiency. It is effective to make a prediction about when and where human exist from data of pedestrian movement and environment. Then, we need to know how the configuration of environment effects pedestrian. This paper presents a measuring system of pedestrian movement tendency, and prediction system of pedestrian movement. We conducted the prediction experiment with real observed data, and proved that system can contribute to the balancing safety and efficiency of operating mobile robot.

Goal-Directed Movement Enhances Body Representation Updating

Body representation refers to perception, memory, and cognition related to the body and is updated continuously by sensory input. The present study examined the influence of goals on body representation updating with two experiments of the rubber hand paradigm. In the experiments, participants moved their hidden left hands forward and backward either in response to instruction to touch a virtual object or without any specific goal, while a virtual left hand was presented 250 mm above the real hand and moved in synchrony with the real hand. Participants then provided information concerning the perceived heights of their real left hands and rated their sense of agency and ownership of the virtual hand. Results of Experiment 1 showed that when participants moved their hands with the goal of touching a virtual object and received feedback indicating goal attainment, the perceived positions of their real hands shifted more toward that of the virtual hand relative to that in the condition without a goal, indicating that their body representations underwent greater modification. Furthermore, results of Experiment 2 showed that the effect of goal-directed movement occurred in the active condition, in which participants moved their own hands, but did not occur in the passive condition, in which participants’ hands were moved by the experimenter. Therefore, we concluded that the sense of agency probably contributed to the updating of body representation involving goal-directed movement.

Strength of Intentional Effort Enhances the Sense of Agency.

Sense of agency (SoA) refers to the feeling of controlling one’s own actions, and the experience of controlling external events with one’s actions. The present study examined the effect of strength of intentional effort on SoA. We manipulated the strength of intentional effort using three types of buttons that differed in the amount of force required to depress them. We used a self-attribution task as an explicit measure of SoA. The results indicate that strength of intentional effort enhanced self-attribution when action-effect congruency was unreliable. We concluded that intentional effort importantly affects the integration of multiple cues affecting explicit judgments of agency when the causal relationship action and effect was unreliable.

The Readiness Potential Reflects the Reliability of Action Consequence

Humans are capable of associating actions with their respective consequences if there is reliable contingency between them. The present study examined the link between the reliability of action consequence and the readiness potential (RP), which is a negative potential observed from about 1–2 s prior to the onset of an action with electroencephalography. In a condition of constant outcome, the participants’ voluntary action always triggered beep sounds; thus, they were able to perceive the contingency between their action and the sound. In contrast, in a condition of inconstant outcome, the participants’ actions only triggered the sound in half the trials. We found that both the early and late RPs were larger in the condition of constant compared to the condition of inconstant outcome. Our results showed that the RPs preceding the voluntary action reflected the reliability of action consequence. In other words, the action-effect contingency enhanced neural activities prior to the action.

Investigating the Relationship Between Assisted Driver’s SoA and EEG

It is important to evaluate and maintain driver’s sense of agency (SoA), because poor SoA of assisted driver may result in slow and inaccurate response in case decisions are required from the driver. This study investigated the relationship between SoA and alpha-band power of EEG in a simulated driving environment.

How anticipation for the sense of agency affects readiness potential

In recent Japanese society, we are facing a severe increase in the number of patients who suffer from motor paralysis and other dysfunctions. Establishing an effective rehabilitation system for them is important, and the key to attain this target is to clarify the mechanisms of ones body perception in the brain. The feeling of controlling our action and external event is an important aspect of body perception, and thus is a topic we have to investigate. This feeling is called the Sense of Agency (SoA), and in order to clarify the mechanism of the SoA, it is necessary to clarify neuro-physiological indices that reflect the arising of this feeling. Recent investigated the relationship between SoA and neural activity with event-related potential (ERP) but these studies focused only on the feedback processing after the action-feedback (e.g. N100, P300), while no study investigated the neural basis of the action-preceding part during SoA paradigm. In this research we focused on feedback-anticipation as an action-preceding factor of SoA, and the purpose of this research is to find a neuro-physiological indices which reflect this factor. We hypothesized that readiness potential (RP) would reflect this factor. In the Libets clock task based experiment, two conditions which differed in the state of the anticipations for the feedback were prepared. In order to manipulate the anticipation, the probability of the tone occurrence was manipulated in each condition. Earlier and larger RP was observed when the feedback-anticipation was inconsistent in relative with the consistent condition, and additional experiment by increasing the sample size is needed. Our study is the first one that reveals the neural basis of the action-preceding factor of SoA, and we believe that our study will contribute to unravel the neural basis of the SoA.

Evaluating effect of sense of ownership and sense of agency on body representation change of human upper limb

To improve rehabilitation of the diseases which are caused by the mismatch between real body and body representation, it is necessary to understand the mechanism of body representation change. It is assumed that sense of agency and sense of ownership are closely-related with body representation and influence body representation change of the body parts without visual information. We focused on human upper limb and performed experiment with participants on four condition related to sensitivity of agency and ownership. We measure perceived position change of elbow and finger by pointing judgement using motion capture. Visual stimulation which participants given is only virtual hand. Our experiment has revealed that sense of agency influence the body representation change on the body parts which is invisible to participants.

Estimation of stress during car race with factor analysis

Car race drivers are always in dangerous and harsh environments. In order to reduce risks due to mental stress, it is important to evaluate stress during a car race in real-time. The present study measured three physiological indices, heart rate variability, sweat rate, and electromyogram of massester from a professional racer during a car race. However, the relation between these indices, and the types of stress still remains unclear. In the present study, we examined the relations between the three indices and factors linked with these indices during car race with factor analysis. The results suggested that the three physiological indices related to two different factors. One factor scored high when driver saw other nearby car, and was influenced mainly by heart rate variability and sweat rate. We suggest that mental stress is probably high in such scenes, and named this factor as “mental stress”. Furthermore, the other factor showed high values during urgent accelerations and decelerations, and was influenced mainly by electromyogram of massester. During urgent accelerations and decelerations, the driver probably suffered from large physical discomfort. Therefore, we named the second factor as “physical stress”. In summary, we found the three physiological indices reflected two different types of stress during car race. Moreover, according to the results of factor analysis, we proposed a method of real-time estimation of both mental and physical stress with the three physiological indices during car race.