PubMed Health⌕ Search

Biomedical subjects

Yoichi Sugita

Publications and source records attributed to Yoichi Sugita.

4 recordsLinked to original sources
PubMed2004

Contextual modulation in the V1 real motion cells.

Retinal images move when the eyes move across a stationary object, or alternatively, when the object moves while the eyes are stationary. Orientation selective cells in V1 showed preference for these two types of retinal image slip. Furthermore, if an orientation cell preferred moving objects, the response to an element of a complex image was modulated by background stimuli placed outside the cell's receptive field. However, the response of cells, that showed no preference for a moving object, was hardly affected by the background. These results indicate that figure and ground are already segregated in the very early stage of visual processing.

Action Potentials↗
PubMed2004

Experience in early infancy is indispensable for color perception.

Early visual experience is indispensable to shape the maturation of cortical circuits during development. Monocular deprivation in infancy, for instance, leads to an irreversible reduction of visually driven activity in the visual cortex through the deprived eye and a loss of binocular depth perception. It was tested whether or not early experience is also necessary for color perception. Infant monkeys were reared for nearly a year in a separate room where the illumination came from only monochromatic lights. After extensive training, they were able to perform color matching. But, their judgment of color similarity was quite different from that of normal animals. Furthermore, they had severe deficits in color constancy; their color vision was very much wavelength dominated, so they could not compensate for the changes in wavelength composition. These results indicate that early visual experience is also indispensable for normal color perception.

Animals↗
PubMed2003

Auditory-visual speech perception examined by fMRI and PET.

Cross-modal binding in auditory-visual speech perception was investigated by using the McGurk effect, a phenomenon in which hearing is altered by incongruent visual mouth movements. We used functional magnetic resonance imaging (fMRI) and positron emission tomography (PET). In each experiment, the subjects were asked to identify spoken syllables ('ba', 'da', 'ga') presented auditorily, visually, or audiovisually (incongruent stimuli). For the auditory component of the stimuli, there were two conditions of intelligibility (High versus Low) as determined by the signal-to-noise (SN) ratio. The control task was visual talker identification of still faces. In the Low intelligibility condition in which the auditory component of the speech was harder to hear, the visual influence was much stronger. Brain imaging data showed bilateral activations specific to the unimodal auditory stimuli (in the temporal cortex) and visual stimuli (in the MT/V5). For the bimodal audiovisual stimuli, activation in the left temporal cortex extended more posteriorly toward the visual-specific area in the Low intelligibility condition. The direct comparison between the Low and High audiovisual conditions showed increased activations in the posterior part of the left superior temporal sulcus (STS), indicating its relationship with the stronger visual influence. It was discussed that this region is likely to be involved in cross-modal binding of auditory-visual speech.

Acoustic Stimulation↗