Publications by authors named "Tomohisa Asai"

In recent years, EEG microstate analysis has attracted much attention as a tool for characterizing the spatial and temporal dynamics of large-scale electrophysiological activities in the human brain. Canonical 4 states (classes A, B, C, and D) have been widely reported, and they have been pointed out for their relationships with cognitive functions and several psychiatric disorders such as schizophrenia, in particular, through their static parameters such as average duration, occurrence, coverage, and transition probability. However, the relationships between event-related microstate changes and their related cognitive functions, as is often analyzed in event-related potentials under time-locked frameworks, is still not well understood.

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The subjective experience of causing an action is known as the sense of agency. Dysfunctional sense of agency over speech has been suggested as a cause of auditory hallucinations. However, agency over speech has not been extensively characterized in previous empirical studies.

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Article Synopsis
  • - Recent advancements in neurotechnology have led to the creation of a real-time EEG-neurofeedback (NF) system that focuses on detecting four key EEG microstates (msA, B, C, and D), which serve as potential biomarkers for certain disorders.
  • - The study tested the NF system's impact on participant performance by introducing delays in feedback, revealing that participants performed significantly better without delay, highlighting the complexities of how different microstates correspond to cognitive abilities.
  • - Although the findings are promising, suggesting immediate improvements in task performance from the NF system, further investigation is needed to understand the long-term effects and specific target behaviors associated with each microstate.
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Article Synopsis
  • The sense of agency refers to the feeling that "I" am responsible for my actions, and its development involves both sensorimotor and cognitive processes.
  • A study combined experimental methods and multivoxel pattern analysis to explore how the brain processes self-agency and self-other attribution.
  • Key findings revealed that the right supramarginal gyrus is particularly sensitive to self-other attribution, while other areas like the precentral gyri focus more on sensorimotor information.
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Developmental body topography, particularly of the face, is a fundamental research topic in the current decade. However, empirical investigation of this topic for very young children faces a number of difficulties related to the task requirements and technical procedures. In this study, we developed a new task to study the spatially-sensed position of facial parts in a self-face recognition task for 2.

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Recently, researchers have focused on the embodied sense of self (ESS), which consists of the minimal and narrative selves. Although a study demonstrated that the ESS is related to brain dysfunction empirically, the subjective aspects of the ESS, and a systematic approach to it, have not yet been examined in brain-damaged patients. To examine this, we measured the ESS of patients with brain tumors before and after awake craniotomy.

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When we drop an object from our hands, we use internal models of both our body height and object-motion to predict when it will hit the floor. What happens if the sensory feedback finally received from the impact conflicts with this prediction? The present study shows that such conflict results in changes in the internal estimates of our body height: When the object people dropped takes longer than expected to hit the floor, they report feeling taller and behave as if their legs were longer. This provides the first evidence of cross-modal recalibration of body-height representations as a function of changes in the distant environment.

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The McGurk effect, which denotes the influence of visual information on audiovisual speech perception, is less frequently observed in individuals with autism spectrum disorder (ASD) compared to those without it; the reason for this remains unclear. Several studies have suggested that facial configuration context might play a role in this difference. More specifically, people with ASD show a local processing bias for faces-that is, they process global face information to a lesser extent.

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Most amputees experience phantom limb, whereby they feel that the amputated limb is still present. In some cases, these experiences include pain that can be alleviated by "mirror therapy." Mirror therapy consists of superimposing a mirrored image of the moving intact limb onto the phantom limb.

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The self includes complicated and heterogeneous functions. Researchers have divided the self into three distinct functions called "agency," "ownership," and "narrative self". These correspond to psychiatric symptoms, behavioral characteristics and neural responses, but their relationship with brain structure is unclear.

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Time perception distorts across different phases of bodily movement. During motor execution, sensory feedback matching an internal sensorimotor prediction is perceived to last longer. The sensorimotor prediction also underlies sense of agency.

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Though the computation of agency is thought to be based on prediction error, it is important for us to grasp our own reliability of that detected error. Here, the current study shows that we have a meta-monitoring ability over our own forward model, where the accuracy of motor prediction and therefore of the felt agency are implicitly evaluated. Healthy participants (N=105) conducted a simple motor control task and SELF or OTHER visual feedback was given.

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Multistability in perception is a powerful tool for investigating sensory-perceptual transformations, because it produces dissociations between sensory inputs and subjective experience. Spontaneous switching between different perceptual objects occurs during prolonged listening to a sound sequence of tone triplets or repeated words (termed auditory streaming and verbal transformations, respectively). We used these examples of auditory multistability to examine to what extent neurochemical and cognitive factors influence the observed idiosyncratic patterns of switching between perceptual objects.

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Anomalous agency has been reported clinically and empirically for people with schizophrenia. This finding is expected to contribute to understanding positive symptomatology in schizophrenia in terms of a general neurocomputational model of motor control, because anomalous agency has also been reported in schizotypal traits in the general population. However, superficially opposite conclusions have been suggested: over-attributed or under-attributed agency in patients.

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Article Synopsis
  • The study explores how the brain perceives ownership and control over limbs through the sensorimotor system, particularly focusing on prosthetic arms.
  • Nine unilateral upper-limb amputees participated, divided into frequent users of their prosthetic arm and those who rarely used it.
  • Results showed that frequent users felt more stable with their prosthesis and had a stronger sense of agency, while rare users experienced instability when using it, suggesting that body awareness influences postural control in amputees.
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The scientific exploration of the self has progressed, with much attention focused on the Embodied Sense of Self (ESS). Empirical studies have suggested the mechanisms for self-representation. On the other hand, less attention has been paid to the subjectivity itself of the self.

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In addition to mental disorders such as attention, emotion, delusions, hallucinations, and difficulties in social skills, the patients with schizophrenia exhibits significant abnormality in sensorimotor perception and control. To seek a neurobiological cause of the heterogeneous symptoms in schizophrenia, we focused on the impaired inference mechanism of the self-agency of the schizophrenia's brain where the sensory outcome generated by the self-initiated action was misattributed to the other agent's action. By developing a novel computational model of agency experience using a Bayesian decision making framework, we united the computational mechanisms of agency and motor control via internal model: a model for one to predict the sensory consequence of action.

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The sense of agency, the subjective experience of controlling one's own action, has an important function in motor control. When we move our own body or even external tools, we attribute that movement to ourselves and utilize that sensory information in order to correct "our own" movement in theory. The dynamic relationship between conscious self-other attribution and feedback control, however, is still unclear.

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The McGurk effect is a well-known illustration that demonstrates the influence of visual information on hearing in the context of speech perception. Some studies have reported that individuals with autism spectrum disorder (ASD) display abnormal processing of audio-visual speech integration, while other studies showed contradictory results. Based on the dimensional model of ASD, we administered two analog studies to examine the link between level of autistic traits, as assessed by the Autism Spectrum Quotient (AQ), and the McGurk effect among a sample of university students.

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Bodily self-consciousness consists of one's sense of agency (I am causing an action) and body ownership (my body belongs to me). Both stem from the temporal congruence between different modalities, although some visuomotor temporal incongruence is acceptable for agency. To examine the association or dissociation between agency and body ownership in the context of different temporal sensitivities, we applied a temporal recalibration paradigm, in which subjective synchrony between asynchronous hand action and its visual feedback can be perceived after exposure to the asynchronous visuomotor stimulation.

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Awareness of our own bodies (sense of body-ownership) and actions (sense of agency) is fundamental for self-consciousness. In the rubber hand illusion, watching a rubber hand being stroked synchronously as one's own unseen hand is also stroked causes the observer to attribute the rubber hand to their own body. The findings of the series of experiments reported here suggest that body-ownership, measured using proprioceptive drift, is elicited by the external acting proxy that drives the sense of agency.

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The sense of body-ownership involves the integration of vision and somatosensation. In the rubber hand illusion (RHI), watching a rubber hand being stroked for a short time synchronously as one's own unseen hand is also stroked causes the observers to attribute the rubber hand to their own body. The RHI may elicit proprioceptive drift: The observers' sense of their own hand's location drifts toward the external proxy hand.

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According to agency memory theory, individuals decide whether "I did it" based on a memory trace of "I am doing it". The purpose of this study was to validate the agency memory theory. To this end, several hand actions were individually presented as samples, and participants were asked to perform the sample action, observe the performance of that action by another person, or imagine performing the action.

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