Biomedical subjects

Sotaro Shimada

Publications and source records attributed to Sotaro Shimada.

3 recordsLinked to original sources

PubMed2006

Infant's brain responses to live and televised action.

Whether human infants perceive televised stimuli in the same way to live stimuli largely remains unknown. Action observation, which has been extensively confirmed to elicit activation of internal motor representation, provides a promising framework for investigating this issue. This 'mirror-matching' property has been found in the monkey premotor cortex as well as the premotor and primary motor cortices in human adults. Although larger activation in observing a live action compared to a televised action in adult subjects has been reported, it is unknown whether the same neural response is obtained from human infants. To address this issue, we first measured the activity of motor areas in adult subjects while viewing either a live or televised action of other people by using near-infrared spectroscopy. The motor areas that were activated when the subject themselves performed an action were also activated during action observation in the live setting, while this was not evident in the TV setting. We then conducted qualitatively the same experiment with 6- to 7-month-old infants. The infant's motor areas were significantly activated when observing a live person performing an action. Although we also found activation in the same area during action observation in the TV setting, the difference in activity between action observation and object-motion observation was significant only in the live setting. Our results are the first to demonstrate activation in motor areas during action observation in human infants. We suggest that human brain responds differently to the real world and the virtual world.

Adult↗

PubMed2004

The parietal role in the sense of self-ownership with temporal discrepancy between visual and proprioceptive feedbacks.

One hypothesis on how we recognize an image of, for example, an arm as our own is through the co-occurrence of multiple sensory feedbacks, especially visual and proprioceptive feedbacks, in this process. It has been suggested that the parietal lobe is the region where proprioceptive and visual information of one's own body is integrated. This study investigated parietal cortical activity during a visual-proprioceptive synchrony judgment task in which visual feedback of the subjects' own passively moving hand was delayed. The subjects were required to judge whether or not there was a delay between the proprioceptive and visual feedbacks. Parietal cortical activity, which was measured using a 48-channel near-infrared spectroscopy (NIRS) apparatus, appeared to be modulated by the length of the delay between the visual and proprioceptive feedbacks. The bilateral superior/middle parietal areas were involved in experiencing the synchrony between the visual and proprioceptive feedbacks, whereas the right inferior parietal areas were strongly activated when discrepancy between the two feedbacks was detected. We postulate that the superior portion of the parietal lobe is essential for maintaining one's own body image, while the right inferior portion is involved in detecting movements of others.

Adolescent↗

PubMed2004

Decrease in prefrontal hemoglobin oxygenation during reaching tasks with delayed visual feedback: a near-infrared spectroscopy study.

Visual feedback of hand movement is crucial to accurate reaching. Although previous studies have extensively examined spatial alteration of visual feedback (e.g., prism adaptation), temporal delay of visual feedback has been less explored. In the present study, we investigated the effect of delayed visual feedback of the moving hand in a reaching task. The prefrontal cortical activity was measured by near-infrared spectroscopy (NIRS). Twelve subjects performed reaching tasks under two conditions where visual feedback of their own hand was delayed by 200 ms (delay condition) or 0 ms (normal condition). Introducing the visual feedback delay significantly disrupted the reaching performance, although the subjects gradually adapted to the delay during the experiment. There was a clear tendency to overreach the target in the delay condition, even after the reaching movement had been practiced sufficiently in the normal condition. We observed marked oxy- and total-Hb decreases in the dorsal prefrontal area in the delay conditions. The decrease began shortly after task onset and diminished during the rest period, indicating that the decrease was task-induced. Furthermore, the oxy- and total-Hb decreases were significantly correlated with task performance--the degree of decrease was larger as the subject made more errors. We suggest that the decreases in oxy- and total-Hb at the dorsal prefrontal area are related with the visuomotor recalibration process.

Adult↗