Yoichi Sugita
Toyohashi University of Technology
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Featured researches published by Yoichi Sugita.
Neuroreport | 1997
Yoichi Sugita
CELLS in the cat primary auditory cortex (A1) were investigated to see whether they could integrate sound signals over time. A1 cells responded well to frequency-modulated sweeps. When a portion of the sweep was replaced by silence the response was weakened considerably. However, the response strength was restored when the silent portion was replaced by a burst of band noise, even though the cells did not respond to the burst of noise alone. These results indicate that A1 cells do not respond simply to instantaneous characteristics of acoustic stimuli but respond to those integrated over time.
Vision Research | 1995
Yoichi Sugita
The relative importance of contrast and assimilation for determining the perceived brightness was estimated. Assimilation decreased when a test spot had such a binocular disparity that the spot and its background appeared on different depth planes respectively. However, contrast was not affected by the binocular depth cue. These results indicate that the cortex takes an important role in assimilation process.
Neuroreport | 1991
Yoichi Sugita; Keiji Tanaka
ALTHOUGH cells in ventral part of the medial superior temporal area (MST) do not respond to movements of a wide textured field, many of them start to respond when a stationary object is placed in front of the moving field. The effective direction in this stimulus configuration is opposite to the preferred direction of individual cells for movement of an object. Here, we examined what stimulus cues were detected by the cells in response to movements of a background pattern behind an object. The responses disappeared when the border of the object was blurred. Because blurring the border degraded an occlusion-related cue, i.e., appearance and disappearance of components of the background at the border, we conclude that the occlusion-related cue is essential for the responses.
Neuroscience Letters | 1996
Ger B. Remijn; Yoichi Sugita
In a tone sequence of continuously ascending frequency or ascending intensity, a tone was occasionally repeated. The repeated tone elicited an anterior negative wave, the latency of which was comparable to the mismatch negativity. However, the amplitude of the negative wave was larger over the left hemisphere than over the right hemisphere. The negative wave might reflect a discrepancy between an expected tone and an actually presented tone.
Neuroreport | 1995
Yoichi Sugita
Visual evoked potentials (VEPs) were recorded during a visual search task to evaluate parallel and serial models of visual processing. A target stimulus elicited a discrete posterior negative wave in the 150–300 ms latency range. Furthermore, there was a close correlation between the search performance and the activity of the negative wave. When the target had a unique feature, neither the search time nor the characteristics of the negative wave was affected by the number of items in display. However, when the target lacked a unique feature, both the search time and the latency of the negative wave increased with the number of items. These results were consistent with a claim that an object with a unique feature is detected preattentively.
Perceptual and Motor Skills | 1994
Yoichi Sugita
During the course of the adaptation to left-right reversed vision, visually evoked potentials (VEPs) were measured for a light flash presented on either side of a fixation. The VEP amplitudes and latencies changed drastically as the adaptation progressed. The time course of the change was quite different between occipital scalp loci. These results indicate that the adaptation to the optical distortion takes place even in the relatively early stage of the visual information processing.
Psychological Research-psychologische Forschung | 1991
Yoichi Sugita; Kazuhiko Mimura
SummaryThe mechanisms that produce simultaneous contrast have been thought to depend on retinal gain control and the retina is supposed to send signals to the brain only in terms of local-border contrast (Shapley, 1986). However, it was found that, when an object on a uniform background and border-concealing stimuli are presented to different eyes, the brightness of the object is greatly influenced if the border-concealing stimuli are perceptually superimposed on the border of the object. The change in the objects brightness in this condition is almost identical to that observed when both the object and the border-concealing stimuli are presented to the same eye, suggesting that the brain can compute brightness by using luminosity information when contrast information is disrupted.
Neuroreport | 1992
Yoichi Sugita
When a part of an image is stabilized on the retina, the part fades to the same colour as its unstabilized surround.1,2 The apparent colour of an empty field is therefore assumed to be equal to the colour of its borders.2 Here, we will show that a similar phenomenon can take place even when the border of a centre field is still visible. A grey square patch with a black frame was surrounded by a coloured background. When the frame had such crossed disparity that the frame appeared in front of the patch, the colour of the patch became perceptually similar to that of the background, indicating that the colour of an empty field is not determined by the colour of its borders alone.
Neuroscience Letters | 1994
Yoichi Sugita
In a visual recognition task for random patterns, event-related potentials (ERPs) were recorded concurrently with the behavioral performance. A prove stimulus, the feature of which was physically different from a sample stimuli to be memorized, elicited a posterior negative wave in the 220-280-ms latency range. Stimulus complexity and longer retention interval decreased not only the accuracy of behavioral performance but also the amplitude of the negative wave. Furthermore, when the subject failed to recognize the difference, the negative wave was not observed. The posterior negative wave might, therefore, reflect traces of visual short-term memory.
Neuroreport | 2004
Yoichi Sugita
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 cells 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.