Biomedical subjects

Jiro Gyoba

Publications and source records attributed to Jiro Gyoba.

13 recordsLinked to original sources

PubMed2006

A new response-time measure of object persistence in the tunnel effect.

The recognition of information about an object is facilitated by a preview of the information concerning that object. This facilitation is regarded as evidence for the representational persistence of the object. It is not known, however, if such facilitation is obtained even under the tunnel effect, in which a moving object is temporarily occluded. This facilitation may be a new way to measure the representational persistence of a moving object in the tunnel effect. We addressed this question by a "same-different" judgment task of a target symbol (" composite function" or "+"), drawn within the moving object, before and after encountering the occluder. Response times (RTs) were shorter when the object reappeared with spatial continuity at the proper place than it reappeared at the improper place, as in Experiments 1 and 3. Thus, facilitation was obtained even in the tunnel effect. When the occluder was invisible and deletion/accretion cues along the contour of the occluder were either removed (Experiment 2) or given improperly (Experiment 4), no facilitation was found. These results clearly indicate that the facilitated recognition was caused by amodal integration of the persisting representation from the unoccluded and modal phases. The present study demonstrates that the facilitated recognition (RT measurement) can be used to investigate the representational persistence in the tunnel effect.

Depth Perception↗

PubMed2006

Characteristics of human luminance discrimination and modeling a neural network based on the response properties of the visual cortex.

Reaction time (RT) and error rate that depend on stimulus duration were measured in a luminance-discrimination reaction time task. Two patches of light with different luminance were presented to participants for 'short' (150 ms) or 'long' (1 s) period on each trial. When the stimulus duration was 'short', the participants responded more rapidly with poorer discrimination performance than they did in the longer duration. The results suggested that different sensory responses in the visual cortices were responsible for the dependence of response speed and accuracy on the stimulus duration during the luminance-discrimination reaction time task. It was shown that the simple winner-take-all-type neural network model receiving transient and sustained stimulus information from the primary visual cortex successfully reproduced RT distributions for correct responses and error rates. Moreover, temporal spike sequences obtained from the model network closely resembled to the neural activity in the monkey prefrontal or parietal area during other visual decision tasks such as motion discrimination and oddball detection tasks.

Adult↗

PubMed2006

The visual phantom illusion: A perceptual product of surface completion depending on brightness and contrast.

The visual phantom illusion was first discovered by Rosenbach in 1902 and named 'moving phantoms' by Tynan and Sekuler in 1975 because of its strong dependence on motion. It was later revealed that phantoms can be generated by flickering the grating (flickering phantoms) or by low-luminance stationary gratings under dark adaptation (stationary phantoms). Although phantoms are much more visible at scotopic or mesopic adaptation levels (scotopic phantoms) than at photopic levels, we proposed a new phantom illusion which is fully visible in photopic vision (photopic phantoms). In 2001, we revealed that the visual phantom illusion is a higher-order perceptual construct or a Gestalt, which depends on the mechanism of perceptual transparency. Perceptual transparency is known as a perceptual product based upon brightness and contrast. We furthermore manifested the shared mechanisms between visual phantoms and neon color spreading or between visual phantoms and the Petter effect. In our recent study, the visual phantom illusion can also be seen with a stimulus of contrast-modulated gratings. We assume that this effect also depends on perceptual transparency induced by contrast modulation. Moreover, we found that the Craik-O'Brien-Cornsweet effect and other brightness illusions can generate the visual phantom illusion. In any case, we explain the visual phantom illusion in terms of surface completion, which is given by perceptual transparency.

Contrast Sensitivity↗

PubMed2006

Presentation of a visual nearby moving object alters stream/bounce event perception.

Two identical visual objects moving across each other in a two-dimensional display can be perceived as either streaming through or bouncing off each other. The bouncing event percept is promoted by the presentation of a brief sound at the point of coincidence of the two objects. In this study, we examined the effect of the presence of a moving object near the two objects as well as the brief sound on the stream/bounce event perception. When both the nearby moving object and brief sound were presented, a streaming event, not a bouncing event, was robustly perceived (experiment 1). The percentage of the streaming percept was also systematically affected by the proximity of the nearby object (experiment 2). These results suggest that the processing of intramodal grouping between a nearby moving object and either of the two objects in the stream/bounce display interferes with crossmodal (audiovisual) processing. Moreover, we demonstrated that, depending on the trajectory of the nearby moving object, the processing of intramodal grouping can promote the bouncing percept, just as crossmodal processing does (experiment 3).

Acoustic Stimulation↗

PubMed2006

Affective impressions and memorability of color-form combinations.

In this study the authors investigate how various impressions affect the recognition of color-form pairs. They performed a preliminary study, a main study of impression rating using the semantic differential method, and a recognition experiment. On the basis of the preliminary study, the authors chose 14 appropriate pairs of adjectives and 48 color and form stimuli and used them for the main study. Factor analysis of the main study extracted three factors: Activity, Potency, and Evaluation. In the recognition test, the authors found that color-form pairs with congruent impressions in Activity or Potency were more easily recognized than pairs with incongruent impressions. In contrast, pairs with incongruent impressions in Evaluation were recognized more easily than congruent pairs. These results are discussed in relation to the assumed network representations of affective impressions that have different characteristics depending on the three factors.

Affect↗

PubMed2004

Multichannel NIRS analysis of brain activity during semantic differential rating of drawing stimuli containing different affective polarities.

We used 24-channel near-infrared spectroscopy (NIRS) to measure activity in the temporal, parietal, and frontal regions of the brain in eight Japanese women while the participants rated line drawings using semantic differential scales. Participants rated the seven line drawings on 15 bipolar semantic scales, each of which belonged to one of three semantic classes: Evaluation, Activity, or Potency. Suzuki et al. [M. Suzuki, J. Gyoba, Y. Sakuta, Multichannel near-infrared spectroscopy analysis of brain activities during semantic differential rating of drawings, Tohoku Psychologica Folia 62 (2003) 86-98.] had reported previously that the right superior temporal gyrus and the right inferior parietal lobule are associated with Activity rating, while the brain regions around the central fissure were related to Potency rating. Based on these suggestions, we investigated the brain activity in these regions during rating of stimuli containing different affective polarities. When drawings were reported as 'static' or 'calm', oxyhemoglobin concentration was higher around the right superior temporal gyrus as compared to when they were considered 'noisy' or 'excitable'. Oxyhemoglobin concentrations around the central fissure were also higher when drawings were rated as 'soft', 'smooth', or 'blunt' compared to 'hard', 'rough', or 'sharp'. Any characteristic oxyhemoglobin changes were not found during the ratings on the evaluation scales. Our results suggest that activation patterns of the temporal and parietal regions are significantly modified by semantic polarities of Activity and Potency.

Adult↗

PubMed2004

Analyzing the aesthetic impressions of alexithymic Japanese students.

We investigated the association between alexithymic tendencies as measured by the 20-item Toronto Alexithymia Scale and the characteristics of aesthetic impressions for words and drawings. Impressions were measured using the semantic differential technique in three groups of Japanese students (High scores n = 31, Moderate scores n = 40, and a Control group n = 182) who were presented only words (Word condition), only drawings (Drawing condition), or pairs comprising one word plus one drawing that represented the same emotional categories (Drawing/Word condition). In a factor analysis on the data from participants, three factors (Evaluation, Activity, and Potency) were extracted. Based on the factor scores, the distances among the three conditions were calculated for each of the groups. For Potency, significant group differences were found between the Drawing/Word and other conditions. In the High-scoring alexithymia group, in particular, the Potency impressions based on tactile sensation, e.g., soft-hard, blunt-sharp, were amplified regardless of stimulus condition. These results are discussed in the context of somatosensory amplification associated with alexithymia and the difficulty of distinguishing between emotion and somatic sensations.

Affective Symptoms↗

PubMed2003

Low doses of alcohol have a selective effect on the recognition of happy facial expressions.

Alcohol is one of the most widely used recreational drugs, yet it is associated with undesirable social behaviour. It is used primarily for its psychoactive properties, increasing sociability and talkativeness. We hypothesize that low doses of alcohol can improve the performance related to positive emotional cognition. In this experiment, we examined the effect of low doses of alcohol on the processing of emotional facial expressions. Fifteen young male volunteers drank alcohol at volumes of 30, 60, 120 ml (0.14, 0.28, 0.56 g/kg) and performed discrimination tasks on morphed facial emotion expressions of anger, happiness, sadness and surprise-neutral. One-way ANOVA co-varying pretreatment performances revealed significant differences between alcohol levels in happy face discrimination ( p<0.01). Bonferroni correction demonstrated that low doses of alcohol caused a significantly better discrimination of happy faces, and that the performances were worse with higher doses ( p<0.001). No significance was observed with the other three emotional faces. These results indicate that low doses of alcohol affect positive emotional cognition of happy facial expressions.

Adult↗

PubMed2003

The effect of prolonged viewing on the recognition of global and local levels of hierarchically constructed patterns.

Two experiments were carried out to examine delays in the recognition of test patterns after prolonged (25 s) viewing of an adaptation pattern which was composed of either the same or different local components and global structures. In the case of geometric patterns that contained a few relatively large elements, there were significant delays of about 70 ms in the global decision task when the test and adaptation stimuli (TS and AS) were of the same pattern, or when they had the same structure but different components. In contrast, in the case of geometric patterns that were composed of many relatively small elements, such a figural relation between the AS and the TS did not affect the recognition speed of the TSs either in the global or in the local decision task. These results suggest that prolonged viewing reduces the efficiency of global processing and that such a disruptive effect occurs depending upon the number and the relative size of the elements that make up the whole pattern.

Humans↗

PubMed2003

Specific brain processing of facial expressions in people with alexithymia: an H2 15O-PET study.

Alexithymia is a personal trait characterized by a reduced ability to identify and describe one's own feelings and is known to contribute to a variety of physical and behavioural disorders. To elucidate the pathogenesis of stress-related disorders and the normal functions of emotion, it is important to investigate the neurobiology of alexithymia. Although several neurological models of alexithymia have been proposed, there is very little direct evidence for the neural correlates of alexithymia. Using PET, we studied brain activity in subjects with alexithymia when viewing a range of emotional face expressions. Twelve alexithymic and 12 non-alexithymic volunteers (all right-handed males) were selected from 247 applicants on the basis of the 20-item Toronto Alexithymia Scale (TAS-20). Regional cerebral blood flow (rCBF) was measured with H(2)(15)O-PET while the subjects looked at angry, sad and happy faces with varying emotional intensity, as well as neutral faces. Brain response in the subjects with alexithymia significantly differed from that in the subjects without alexithymia. The alexithymics exhibited lower rCBF in the inferior and middle frontal cortex, orbitofrontal cortex, inferior parietal cortex and occipital cortex in the right hemisphere than the non-alexithymics. Additionally, the alexithymics showed higher rCBF in the superior frontal cortex, inferior parietal cortex and cerebellum in the left hemisphere when compared with the non-alexithymics. A covariance analysis revealed that rCBF in the inferior and superior frontal cortex, orbitofrontal cortex and parietal cortex in the right hemisphere correlated negatively with individual TAS-20 scores when viewing angry and sad facial expressions, and that no rCBF correlated positively with TAS-20 scores. Moreover, the anterior cingulate cortex and insula were less activated in the alexithymics' response to angry faces than their response to neutral faces. These results suggest that people with alexithymia process facial expressions differently from people without alexithymia, and that this difference may account for the disorder of affect regulation and consequent peculiar behaviour in people with alexithymia.

Adult↗

PubMed2003

[Analyzing the factor structure and the sensory-relevance of impressions produced by words and drawings].

The impressions of words and drawings that represented the same concepts (joy, anger, tranquility, etc.) were examined by the semantic differential technique. In the word (W) condition where the participants were presented with only the word stimuli, two factors (Evaluation and Activity) were extracted. By contrast, in the drawing (D) condition where the participants only saw the drawings, three factors (Evaluation, Activity, and Potency) were extracted and the potency factor was found to have large factor loadings for the adjective-pairs containing high relevance to tactile sensation. The same tendencies were found in the drawing + word (DW) condition where the drawings and the words were presented simultaneously. These results revealed that the factor structure in the W condition differed from those in the D and the DW conditions, and that the drawings aroused tactile sensations. Further analysis in the evaluation factor implied that the impressions produced in the DW condition had unique characters that could not be reduced to those in the W and the D conditions.

Emotions↗

PubMed2002

Selective attention to stimulus features modulates interocular suppression.

Psychological and neurophysiological studies have shown that attention modulates various sorts of perceptual processing. Here, we report that attention affects the perceptual dominance of binocular rivalry. Experiments using a dichoptic masking paradigm revealed that when an observer was attending to one of the two orientations of the elements of a monocular texture, a texture briefly presented to the opposite eye suppressed the perception of the elements with the attended orientation, while the elements with the orientation which was ignored sustained their dominance. Moreover, subsequent experiments indicated that the suppression depended on the orientation of the texture elements constituting the mask, but was independent of their locations. These results suggest that attention to specific features modulates interocular suppression in a mode which is different from that found in a previous study [Ooi and He, 1999 Perception 28 551 -574].

Attention↗

PubMed2002

[Analyses of responsible factors for the delay effect produced by prolonged viewing in recognizing Kanji characters].

Ninose & Gyoba (1996) examined delays in the recognition of Kanjis following prolonged viewing. They suggested that a Kanji pattern may be internally represented as a whole and the prolonged viewing may produce an adaptation effect specific to such a representation. The present study examined responsible factors producing the delay effect more in detail by manipulating figural components of adaptation and test Kanjis. The delay occurred only when the test Kanji was the same pattern as the adaptation Kanji in all local details. In contrast, the delay were not observed either when the global pattern of the test Kanji was similar to that of the adaptation Kanji, or when a part of the test Kanji was the same pattern as the whole configuration of the adaptation Kanji. These results indicate that the delay effect is produced by prolonged viewing of the adaptation Kanji with exactly the same local and global configurations as the test Kanji, while the previous studies have revealed that the delay effect occurs independent from Kanji's size and orientation in some ranges.

Adaptation, Psychological↗