Biomedical subjects

Masahiro Hirai

Publications and source records attributed to Masahiro Hirai.

6 recordsLinked to original sources

PubMed2006

Visual search for biological motion: an event-related potential study.

To investigate the neural response to detection of biological motion (BM) surrounded by distractors, event-related potentials (ERPs) were recorded. Scrambled motion with the same velocity vector as the BM but randomized initial starting points was used as the distractor. The number of distractors was varied to control the difficulty of the task. The behavioral data showed that the reaction time increased with the number of distractors. Moreover, the ERP results showed that enhanced negativity was elicited at posterior electrodes contralateral to the location of the BM as with the conventional N2pc-like component, which is related to selection of the target. The increment of reaction time indicated that the attentional process is involved in the detection of BM. Furthermore, the ERP waveforms suggest that, even when detection of the target requires form-from-motion processing, similar neural mechanisms to those involved in conventional visual search tasks were employed here.

Adult↗

PubMed2005

The relative importance of spatial versus temporal structure in the perception of biological motion: an event-related potential study.

We investigated how the spatiotemporal structure of animations of biological motion (BM) affects brain activity. We measured event-related potentials (ERPs) during the perception of BM under four conditions: normal spatial and temporal structure; scrambled spatial and normal temporal structure; normal spatial and scrambled temporal structure; and scrambled spatial and temporal structure. As in a previous study, we identified two negative components at both occipitotemporal regions: N210 reflected general motion processing while N280 reflected the processing of BM. We analyzed the averaged ERPs in the 200-300 ms response time window and found that spatial structure had a substantial effect on the magnitude of the averaged response amplitude in both hemispheres. This finding suggests that spatial structure of point-lights elicits a stronger response in the occipitotemporal region than temporal structure for the BM perception.

Adolescent↗

PubMed2005

Active processing of biological motion perception: an ERP study.

The purpose of this study was to measure event-related potentials (ERPs) to clarify how attention affects neural activity during the visual perception of biological motion (BM). Thirteen healthy subjects observed BM or scrambled motion (SM). For SM, each point had the same velocity vector as in BM, but the initial starting positions were randomized. Each BM and SM was overlaid with ten noise dots and four rectangles. For the rectangles, one was or was not rotated 90 degrees relative to the others. Subjects were required to undertake two kinds of visual tasks. For the attention-to-motion condition, subjects directed their attention to the type of motion. For the attention-to-rectangle condition, subjects directed their attention to the rotational angle of the overlaid rectangles. As in our earlier study, the ERP response to the perception of BM had two negative components at approximately 200 ms (N200) and approximately 330 ms (N330) in both attentional conditions. Our analysis focused on the amplitude of the second negative component, which was sensitive to BM. There was a significant interaction between attention and the type of motion regarding the amplitude of N330. Specifically, the amplitude of N330 in response to BM was greater in the attention-to-motion condition than in the attention-to-rectangle condition, and was greater than the amplitude of the response to SM in the attention-to-motion condition. These results suggest that in this experimental design, processing of BM is modulated by attention.

Adolescent↗

PubMed2005

An event-related potentials study of biological motion perception in human infants.

To clarify the dynamical processing aspect of biological motion (BM) perception from a developmental point of view, we measured event-related potentials (ERPs) in 8-month-old infants during the perception of BM or a scrambled motion (SM; randomization of BM's spatial structure). We found that activation of the right hemisphere in 8-month-old infants was similar to that of adults, suggesting that the neural substrates for processing BM perception begin to mature at around 8 months of age.

Analysis of Variance↗

PubMed2004

Neural dynamics in human imitation revealed by ERP surface topography.

To clarify the neural dynamics in human motor imitation, we examined event-related potentials (ERP) for a reaction time task that required responses to an actor's finger motions with identical motions. Compared with a control task (reaction to an LED illumination), the ERP surface topography in the imitative reaction was differentiated at around 120-200 ms post-cueing, showing an early sensitivity to the response hand over the pre-central region. This result suggested that activities around the motor areas were facilitated in the imitative reaction, which is consistent with recent neuroimaging studies. However, taken together with that there were no differences in reaction times, the early ERP latency of conditional divergence indicated that neural activities related to imitation are visual responses and do not directly lead to motor acceleration.

Adult↗

PubMed2003

An event-related potentials study of biological motion perception in humans.

In order to clarify the neural dynamics involved in the perception of biological motion, we recorded event-related potentials from 12 subjects. The subjects were shown biological motion or scrambled motion as a control stimulus. In the scrambled motion, each point had the same velocity vector as in the biological motion, but the initial starting positions were randomized. The perception of both biological and scrambled motion elicited negative peaks at around 200 (N200) and 240 ms (N240). Furthermore, both negative peaks were significantly larger in the biological motion condition than in the scrambled motion condition over the right occipitotemporal region. In light of previous human neuroimaging studies, we speculate that component N200 is generated near the extrastriate cortex area and N240 is generated from the superior temporal sulcus region.

Adult↗