Shuntaro Okazaki

• Ph. D.
• Senior Researcher at Shiseido Mirai Development Institute

Despite the multiple regions and neural networks associated with value-based decision-making, the orbitofrontal cortex (OFC) is possible a particularly important one. Although the role of the OFC in reinforcer devaluation tasks, which assess the ability to represent identity, sensory qualities, and subjective values of the expected outcomes, has be...

Astrocytes are thought to play a crucial role in providing structure to the spinal cord and maintaining efficient synaptic function and metabolism because their fine processes envelop the synapses of neurons and form many neuronal networks within the central nervous system (CNS). To investigate whether putative astrocytes and putative neurons distr...

The use of face masks has become ubiquitous. Although mask wearing is a convenient way to reduce the spread of disease, it is important to know how the mask affects our communication via facial expression. For example, when we are wearing the mask and meet a friend, are our facial expressions different compared to when we are not? We investigated t...

Sharing experience is a fundamental human social cognition. Since visual experience is a mental state directed toward the world, we hypothesized that sharing visual experience is mediated by joint attention for sharing directedness and mentalizing for mental state inferences. We conducted a hyperscanning fMRI with 44 healthy adult volunteers to tes...

The use of face masks has become ubiquitous. Although mask wearing is a convenient way to reduce the spread of disease, it is important to know how the mask affects our communication via facial expression. For example, when we are wearing the mask and meet a friend, are our facial expressions different compared to when we are not? We investigated t...

How coherent neural oscillations are involved in task execution is a fundamental question in neuroscience. Although several electrophysiological studies have tackled this issue, the brain-wide task modulation of neural coherence remains uncharacterized. Here, with a fast fMRI technique, we studied shifts of brain-wide neural coherence across differ...

Psychological stress activates the hypothalamus, augments the sympathetic nervous output, and elevates blood pressure via excitation of the ventral medullary cardiovascular regions. However, anatomical and functional connectivity from the hypothalamus to the ventral medullary cardiovascular regions has not been fully elucidated. We investigated thi...

Understanding others as intentional agents is critical in social interactions. We perceive others' intentions through identification, a categorical judgment that others should work like oneself. The most primitive form of understanding others' intentions is joint attention (JA). During JA, an initiator selects a shared object through gaze (initiati...

Seizures are induced when subjects are exposed to severe hypoxia. It is followed by ventilatory fall-off and eventual respiratory arrest, which may underlie the pathophysiology of death in patients with epilepsy and severe respiratory disorders. However, the mechanisms of hypoxia-induced seizures have not been fully understood. Because astrocytes a...

Teachers often believe that they take into account learners' ongoing learning progress in their teaching. Can behavioural data support this belief? To address this question, we investigated the interactive behavioural coordination between teachers and learners during imitation learning to solve a puzzle. The teacher manually demonstrated the puzzle...

Automatic mimicry is a critical element of social interaction. A salient type of automatic mimicry is eye contact characterized by sharing of affective and mental states among individuals. We conducted a hyperscanning functional magnetic resonance imaging study involving on-line (LIVE) and delayed off-line (REPLAY) conditions to test our hypothesis...

During joint action, two or more persons depend on each other to accomplish a goal. This mutual recursion, or circular dependency, is one of the characteristics of cooperation. To evaluate the neural substrates of cooperation, we conducted a hyperscanning functional MRI study in which 19 dyads performed a joint force-production task. The goal of th...

[Purpose] Electromyography biofeedback therapy is applied to various diseases during physical therapy for motor learning. Our aim was to develop a low-cost electromyography biofeedback device kit that students could build by themselves in class and to evaluate whether this kit was an adequate educational tool for physical therapy students. [Subject...

Social interactions can be facilitated by action-outcome contingency, in which self-actions result in relevant responses from others. Research has indicated that the striatal reward system plays a role in generating action-outcome contingency signals. However, the neural mechanisms wherein signals regarding self-action and others’ responses are int...

PurposeTo spread the use of EMG biofeedback devices, we have developed a simple and lowcost electromyography EMG biofeedback device that can be used with the latest model of smartphones and tablet terminal LCEMG. The specific purpose of this study was to verify whether the performance of the LCEMG fulfills the requirement of the use in EMG biofeedb...

Objective: For the convenient use of electromyography devices in physical rehabilitation during locomotion, we developed a simple, low-cost 2-channel electromyography telemeter (LC-EMGT) that can be connected wirelessly with a personal computer (PC) microphone port. The aim of this study was to verify whether the performance of our LC-EMGT fulfills...

The ventromedial hypothalamus (VMH) is known to play an important role in feeding behavior and the control of sympathetic nerve activity (SNA). We report the identification of novel neuron groups that showed oscillations on both sides of the VMH in hypothalamus slice preparations from juvenile rats of postnatal days 5-14. We detected spontaneous rh...

Abnormal pattern of brain activation of adults with developmental stuttering in view of the neural model of katakana word reading. In order to elucidate the neural basis of stuttering, a model of reading was firstly determined and secondly applied to people who stuttered (PWS) in functional MRI experiments. Japanese native speakers read aloud famil...

During a dyadic social interaction, two individuals can share visual attention through gaze, directed to each other (mutual gaze) or to a third person or an object (joint attention). Shared attention is fundamental to dyadic face-to-face interaction, but how attention is shared, retained, and neutrally represented in a pair-specific manner has not...

People's behaviors synchronize. It is difficult, however, to determine whether synchronized behaviors occur in a mutual direction—two individuals influencing one another—or in one direction—one individual leading the other, and what the underlying mechanism for synchronization is. To answer these questions, we hypothesized a non-leader-follower pos...

Affective mentalizing involves the integration of various social signals in order to infer the affective states of others. Previous neuroimaging studies have shown that the medial prefrontal cortex, the precuneus/posterior cingulate cortex, and the temporo-parietal junction constitute the core affective mentalizing network. However, the relative co...

In adults, sleep is necessary for the offline improvement of certain skills, such as sequential finger tapping, but whether children show a similar effect is still debatable. Here, we tested whether sleep is associated with offline performance improvement in children. Nine-and 11-year-old children trained on an explicit sequential finger tapping ta...

The auditory-vocal system modifies voice fundamental frequency (F0) with auditory feedback. The responses to F0 changes in auditory feedback are known to depend on the task. The hypothesis explored in this study is that the task dependency is the result of multiple components of the F0 responses differently modulated with different tasks. Attention...

Motor skill memory is first encoded online in a fragile form during practice and then converted into a stable form by offline consolidation, which is the behavioral stage critical for successful learning. Praise, a social reward, is thought to boost motor skill learning by increasing motivation, which leads to increased practice. However, the effec...

Akaike's Noise Contribution Ratio (NCR) has been used for the analysis of causality of two-variable settings of biological time series in Neuroscience. In contrast to the conventional correlation definition, this methodology is able to detect the direction of the influence between two variables. However, if a third series intervention is taken...

A study was conducted to propose an analytical method for assessing temporal interference of speech by delayed auditory feedback (DAF) quantitatively and in isolation. Fifteen native Japanese speakers, including 8 males and 7 females aged between 19-31 years participated in this experiment. Participants were seated comfortably on a chair in a sound...

The dorsal part of Broca's area has been considered to be involved in grapheme-to-phoneme conversion based on more intensive activation by pseudowords and low-frequency words than high-frequency words of alphabetic languages. In the present study, we used low and high familiarity words, and pseudowords, presented in Katakana, to investigate the Bro...

Fundamental frequency (F0) of our vocalization is regulated by auditory feedback. Manipulation of F0 in the auditory feedback invokes compensatory F0 response in vocalization, whose amplitude is known to depend on the task (singing or speaking; instruction to follow/ignore the heard pitch change) and the averaged F0. In order to exclude the volunta...

Mismatch negativity (MMN) is a negative component of event-related brain potentials elicited by stimulus transitions. Stimulus duration transition also elicits MMN (duration MMN), with a magnitude that is related to the degree of duration change and the discrimination ability. The neural substrates of duration MMN have not yet been investigated. We...

An event-related potential called mismatch negativity is known to exhibit physiological evidence of sensory memory. Mismatch negativity is believed to represent complicated neuronal mechanisms in a variety of animals and in humans. We employed the auditory oddball paradigm varying sound durations and observed two types of duration mismatch negativi...

Unit discharges and local field potentials (LFPs) were recorded simultaneously in primary auditory cortex (A1) of a guinea pig for cross-correlograms and cross correlation functions of LFPs were compared. From the results, the adequate periods of signals applied for cross correlation analysis were discussed. Consequently this application period mus...

We studied how hippocampus affects auditory cortex neurons by means of single-unit recording. The population of responses to click-sound in the guinea-pig auditory cortex was estimated by resampling method, and the effects on neural response of hippocampal activation that evoked by electrical stimulation were determined. As a result, the firing rat...