To avoid obstacles, the brain may use optic flow for locomotor control or it may simply use the perceived direction of an obstacle. We tested these hypotheses in an immersive virtual environment using Warren et al.'s (2001) method where optic flow is displaced from the direction of locomotion provided by somatosensory information. To steer the body around a vertical axis, locomotor control depends on the optic flow with a focus of expansion (FOE) on the obstacle, suggesting that the brain uses optic flow to avoid an obstacle.
A tactile stimulus generates different sensations, depending on the delivery source. The rubber hand illusion (RHI), a phenomenon where a touch to one's hand is perceived to come from a fake hand, reflects the role of a multisensory interaction in a coherent body representation. Although this phenomenon has been mostly studied with an experimenter providing tactile stimuli, here we investigate whether a tactile stimulus must be externally produced for RHI to occur. By introducing the condition where a participant touches an artificial hand and his/her own hand simultaneously, the results demonstrate that illusion still occurs, but the perceived amplitude is smaller than that in the ordinal externally produced touch condition. Our results suggest that the externally produced tactile sense is not required for RHI. Further studies are necessary to elucidate the cause of the decreased illusion with the self-produced tactile stimulation.
Auditory stimuli are known to alter visual perception. However, the effects of such stimuli on velocity perception have not yet been examined. A well-known velocity illusion related to object size is described by Brown's law. We can easily match object size with sound intensity. Therefore, this study examined the potential modification of velocity perception by auditory stimuli at different sound pressure levels (SPLs). The results showed that the perceived velocity, particularly when the object size was small, diminished with a high SPL auditory stimulus. We assume two interpretations of this result. First, high intensity sounds can modify the perceived object size and alter the perceived velocity by replicating Brown's law since large objects tend to match well with high SPL sounds. Second, previous studies indicated that stimuli with strong intensities seem to have been presented for longer durations. Thus, stimulus duration may be perceived as longer when higher SPL sounds are presented simultaneously, which may cause the velocity to be perceived as being slower.
A Ternus display is a type of apparent motion stimulus in which the perceived motion of the constituent elements is bistable; two types of apparent motion are sensed depending on the temporal parameter (the inter-frame interval) of the stimulus sequence. This study employs Gabor patches as elements of the Ternus display to investigate the effect of an element's spatial frequencies on the apparent motion. The perceived motion strongly depends on the location of the element with a lower spatial frequency for a Ternus display composed of patches with different spatial frequencies. The results are discussed in terms of the interactions of the motion signals between the elements.
We examined the effect of adaptation to a static stimulus and a moving stimulus on motion-induced blindness (MIB). In Experiments 1 and 2, a static stimulus was presented at 0, 5, or 10s prior to the onset of the moving stimulus. (In Experiment 3, stimulus was presented 0, 1, 3, or 5s prior.) Adaptation to the static stimulus decreased the latency of MIB regardless if the adaptation stimulus, which was viewed with one eye, was presented to the same or other eye after the onset of the moving stimulus (Experiment 1). An adaptation effect was not obtained when the location of a binocularly adapted stimulus changed at the onset of the moving stimulus (Experiment 2). Moreover, the effect was marginal for the stimulus adapted for 3s (Experiment 3). In Experiment 4, the presentation of the moving stimulus occurred 20s prior to the onset of the static stimulus. Adaptation to a moving stimulus prolonged the disappearance latency of MIB. Based on these results, we discussed possible mechanisms of MIB.
Bayesian analysis is applied to experimental data to effectively exploit information by the up-down method. Comparing Bayesian analysis to the standard one, which estimates the point of subjective equality (PSE) by averaging part of the comparison stimuli, confirms the two methods do not differ in terms of the PSE estimation. However, the standard analysis estimates only the PSE, whereas Bayesian analysis can also estimate a just noticeable difference (JND). Estimates of the PSE and JND determine a psychometric function. These results reveal that the Bayesian analysis is useful and superior to the standard analysis.
If the probability that a target item in a visual task is presented at a given location or with a given feature is high, the reaction times for biased targets are shorter than those for low probability targets. However, the relationship between manipulation of probabilistic information and this probability effect is unclear. In this study, we investigated the effects of the spatial and nonspatial probabilities associated with the onset of targets on attentional deployment. When targets appeared at high probability locations, reaction times for target discrimination were faster than those that appeared at less likely locations (Experiment 1). However, such a probability advantage did not appear when the targets' appearances were associated with the shapes of the placeholders, regardless of their locations (Experiment 2a). The probability effect reoccurred when participants were informed of the nonspatial probabilistic manipulation (Experiment 2b). These results suggest that the spatial probability is effective as an attentional cue without awareness, whereas the nonspatial probability is not.
Object recognition involves perceptual decisions, such as detection, discrimination, identification and categorization. We investigated which stimulus' properties are involved in these decisions using stimuli from Snodgrass and Vanderwart (1980) modified by random-noise. Each experiment examined a different perceptual decision. In Experiment 1, observers performed a detection task, and detection thresholds were measured. In Experiments 2, 3 and 4, discrimination, identification and categorization tasks were performed, respectively, and the accuracy and RTs were measured. The correlations between measurements (i.e., the detection thresholds, accuracy and RTs) and object variables, such as the number of pixels, the degree of circularity and visual complexity, indicated that detection is correlated with the perception of the local edge. Discrimination decisions involved the comparison of salient parts of the objects, and identification and categorization decisions involved a wide range of visual processing (i.e., the perception of the local edge, visual complexity and image agreement).
Common marmosets (Callithrix jacchus) have a small body-size (adults weigh 250-450g) and originate from the rainforests in Brazil. Common marmosets have been used extensively in Neuroscience and biomedical research because of their high fertility, biosafety, ease of handling, and low cost of breeding when compared to other non-human primates. However, the recent success in the generation of transgenic marmosets with germline transmission has made marmosets vastly more important as experimental nonhuman primate models for human diseases. In addition to the possibility of genetic modification, a large repertoire of behavior can make marmosets of value as experimental animals in Social Neuroscience. They show some unique features, which even macaques and chimpanzees never show. Typically in marmosets, just like "family" in human, one pair of a dominant female and male in each group monopolize the reproduction. The breeding female produces litters of 2-3 infants (birth weight approximately 30g) at roughly 6-month intervals. The energy and ecological demands of rearing 2 "heavy" infants has been suggested as the cause for the existence of a cooperative breeding system; not only mothers but also fathers, brothers, and sisters take care of infants. They often rely on vocalization to communicate each other. They often show food transfer behavior (food transfer from parents to infants). They have a high level of mutual gaze. Because of the small body-size, we can keep them as a "family" in a colony and produce various social situations in experimental rooms. I would like to introduce the potential of common marmosets as experimental animals in Social Neuroscience as well as biomedical studies.
Odor hedonics is not consistent among individuals. Making products such that their odor is accepted by any consumer has been very difficult in the industrial world. It is important to know how preference to odors is acquired. One of the reasons for such a diversity of odor hedonics is that it depends on the diversity of its perception. Perceived odor qualities widely range among individuals. It might come from different aspects in the focus of attention to olfactory input. Most odors in everyday-life are a mixture constructed from various odor chemicals. There has been little research investigating how we smell and recognize such complicated bottom-up olfactory information. Moreover olfaction often undergoes an interaction with other sensory modalities. In the present article we report that the shape of the product may affect odor impression.
Characteristics of visual attention related to the safety are discussed from two aspects based on our research. The first one concerns eye movements and useful field of view (UFOV). This is the first attempt to examine UFOV in free eye movements under real behaviour. The narrowing of UFOV with increase of demand (complexity of situations) and a trade-off between depth and width of processing in UFOV were found. Supplementary the effect of ageing on UFOV is introduced. The ageing effect is largest in detection of irregular peripheral targets under dual task of central and peripheral detection. The second one concerns attention shift in depth (different distances) in an observer-moving situation. No previous research like this was performed. The results clearly showed that reaction time of shift of attention from far location to near location is shorter than the reverse. We call this "rubber band metaphor of attention" (asymmetrical viewer centred mode of attention shift). The difference is larger in moving condition than in stationary condition. This result is reasonable for drivers' safety and ecologically valid. It should be stressed that it is more promising to conduct experiments on visual attention in behaviour oriented situations.
At present, environmental noises are evaluated by sound intensity such as equivalent continuous A-weighted sound pressure level (L_<Aeq>). However, we sometimes feel annoyed with sound with low sound intensity because of the quality. Sound quality can be characterized by factors obtained from autocorrelation (ACF) and interaural cross-correlation function (IACF) of sounds. For example, pitch and pitch strength can be characterized by the delay time (τ_1) and amplitude of the maximum peak (φ_1) of the ACF. Directional sensation can be characterized by the delay time (τ_<IACC>) and amplitude of the maximum peak (IACC) of the IACF. We utilized ACF and IACF factors as means to evaluate artificial and environmental noises. The results suggest that the effective duration of the ACF, τ_1, φ_1, and IACC are useful criteria for evaluating noise.
The author summarized new systems to measure visual functions. The event related brain potential (ERP) has been used as an index of visual functions. Visual ERP, however, has difficulties in application to practical fields. Eye movements are restricted in a study of visual ERP. The author found unique ERP associated with offset of saccadic eye movements. We can obtain the ERP with averaging EEG at offset of saccades; i.e., onset of eye fixations. The ERP is called eye fixation related potential (EFRP). The author and colleagues have developed some systems to measure EFRP. For example, a system is a real time analyzer of EFRP, a system to show topography of EFRP, and topography of EFRP in real time. We have applied systems to assess visual attention, visual workload and visual fatigue. Recently, we developed a new system to obtain topography of EFRP to a visual object identified precisely eye positions. The system will be applicable as indices of assessment of attention in traffic fields and preference of a consumer to a visual object in marketing.
The mechanisms of auditory perceptual organization play important roles in music composition and music listening. In some composition techniques, such as 'hocket' and 'pseudo-polyphony', several Gestalt principles are employed to give special effects of tonal grouping. In the process of the perceptual segregation, our auditory system can produce the percept by reconstruction of sound events and sub-events.
I discussed cognitive processing of music in the brain through a neuropsychological approach. The case 1 showed an impairment of chord perception and, in singing familiar songs, replacement of phrases (paramelodia), due to infarction of anterior portions of bilateral temporal lobes. We performed a positron-emission-tomogoraphy (PET) activation study in order to clarify the brain regions which participated in chord perception. As a result, anterior portions of bilateral temporal lobes were activated. We can reasonably conclude that these brain regions have a relationship with chord perception. The case 2 had infarction of bilateral temporal lobes, and revealed word deafness, environmental sound agnosia, and receptive and expressive amusia. Though the patient showed impaired scores in tasks of chord and pitch discrimination, recognition of tonality was normal. Though the patient showed impaired scores in tasks of chord and pitch discrimination, recognition of tonality was normal. Tonality turned out to be one of the independent factors of receptive processing of music. We revised the Peretz's model of music processing in the brain.
It is well-known that music activities can stimulate the brain and the body, thus enhancing the quality of life. However, little experimental evidence has been accumulated for positive effects of music therapy. Recent research is reviewed to examine how music therapy can be used for schizophrenia patients.
The visual system integrates or segregates two motion components in the same visual field depending on direction difference. We examined how the surrounding motion modulates such integration or segregation. In the experiment, participants were presented with motion components in two nearby directions (e.g., ±45 deg from vertical). We found that participants reported two segregated motions more frequently when the direction of the surrounding motion was equivalent to the averaged direction of central motions. In contrast, participants reported one integrated motion when the direction of the surrounding motion was opposite that of the center. The present results suggest that motion integration and segregation was determined based on a representation of motion direction modulated by the surrounding motion.
We demonstrated that good continuity, or amodal collinear connectivity, generates an integrated object from component arcs and this integration brings motion binding (Lorenceau & Shiffrar, 1992). Therefore, the existence of corners is not a required factor for motion binding. We presented to observers either a circle or a four-pointed star composed of four arcs with occluders. Motion binding was perceived for both configurations. However, the bound shape appeared rigid with stars, but appeared elastic with circles. This difference probably arises from less tolerance for fluctuation in integration based on continuity than that in integration based on corners.
De Valois and De Valois (1991) showed that individuals perceive a shift in the position of a static Gabor patch with a moving carrier in the direction of motion inside the stimulus. In our previous study, we showed that illusory position shifts were induced in the direction of carrier motion on the retina. Here, we investigate the effects of envelope motion on the display and examined position shifts when the envelope and carrier moved independently. The results revealed that the envelope-relative motion rather than the display-relative motion induced illusory position shifts.
It has been suggested that visual attention spreads along an object's contour. We investigated the role of contour on attentional spreading. As an index of spreading, we applied the same-object effect, where observers respond faster to targets within cued objects than those within uncued objects. The stimuli consisted of two rectangular objects, both of which were missing one long side. The task was to detect a target that appeared at the end of either a cued or uncued object. In both Experiments 1 and 2, the same-object effect was decreased when the cued object was missing the side faced the uncued object. Moreover, this tendency was more obvious when the uncued object was also missing the side faced the cued object. These results suggest that attention spreads from the opening of the cued object to the uncued object, like a "liquid."
When an apparent motion stimulus with an ambiguous direction in the retinal image is presented during smooth pursuit eye movements, the dominant perceived direction is opposite to the direction of eye movement (Terao et al., 2009). Here we report that pursuit of a stimulus characterized either by continuous ambiguous motion or by discrete apparent motion facilitates retinal motion opposite to the direction of the pursuit. This finding suggests that pursuit enhances motion signals in the opposite direction of the pursuit relative to signals in the same direction. We then investigated how stimulus contrast affected motion perception during pursuit because a previous study reported that sensitivity to the contrast of luminance grating was reduced for signals moving in the opposite direction of the pursuit (Schutz et al., 2007). Our results demonstrated that the perceived direction was opposite to the pursuit direction when the grating contrast was high, whereas the perceived and pursuit directions were the same when the grating contrast was low. This result indicates that pursuit has different effects on motion signals depending on the level of stimulus contrast.
Our ability to recognize surface qualities and infer the materials that make up objects allows us to interact appropriately with the objects. Little is known, however, about the mechanisms of material representation in the brain. In this study, we investigated how information about various materials is processed in the brain using a combination of multivoxel pattern analysis of functional magnetic resonance imaging data and perceptual and image-based physical measures of material properties. We found that information about materials is transformed from image-based representations in early visual areas into perceptual category representations along the ventral pathway.
Under high perceptual load that is assumed to reduce cognitive resources, selective attention is improved because no spare resources are left for distractor processing. Are cognitive resources also consumed under high stress circumstances? The present study examined whether perceptual load and acute stress share a common attentional resource by manipulating perceptual and stress loads. Participants identified a target embedded in an array of nontargets, flanked by compatible or incompatible distractors. Prolonged reaction time to the incompatible relative to compatible flankers was used as an index of interference. Participants in the stress group received a speech test that increased anxiety and threatened self-esteem. The effect of perceptual load interacted with stress manipulation. Participants in the control group demonstrated substantial interference with low perceptual load, whereas such interference was eliminated with high perceptual load. Importantly, the stress group showed virtually no interference with low perceptual load whereas substantial interference occurred with high perceptual load. These results suggest that perceptual and stress loads consume the same attentional resources.
We examined the effect of expanding and contracting motion on visual short-term memory (VSTM) by using a change-detection task. One, three, five, or seven expanding or contracting line segments were presented on memory and test displays. The test display was either identical to the memory display or contained a line segment with a different orientation from that in the memory display. The participants were asked to indicate whether the orientation of the line segments changed between the two successive displays. The results showed that the capacity of VSTM for expanding motion was larger than that for contracting motion (Experiment 1). Moreover, in Experiment 2, the capacity of VSTM for expanding motion was superior when the retention interval between the memory and test displays was 400ms. In contrast, under retention intervals of longer than 800ms, VSTM capacity for contracting motion was superior. These results suggest that the effect of expanding and contracting motion on VSTM varies depending on the retention interval.
One form of synesthetic perception involves the existence of non-arbitrary mapping between linguistic sounds and visual shapes (the so-called bouba/kiki effect). The mechanisms underlying such synesthetic percepts are unclear. Here we report that this synesthetic association is triggered by phonological activation during normal on-line lexical processing. We designed an implicit interference task in which participants made lexical decisions about Japanese non-words presented in shapes. Consonant sounds of the non-words and the visual shapes were either synesthetically matched or mismatched. The non-words were written in either Japanese phonetic Hiragana script or logographic Kanji script. Generally, phonology is thought to mediate lexical access to Hiragana words but not Kanji words. Our results identified synesthetic associations only with non-words in Hiragana script, suggesting that phonological activation during lexical processing is associated with supra-modal processing.
The understanding of self based on facial information may emerge earlier than that based on other body parts because the face is often regarded as the primary physical embodiment of self, at least for adults. Although researchers have hypothesized that the level of understanding of self differs with age, the idea that self differs with body parts has not been examined. This study investigates whether the understanding of self in infancy differs with respect to body parts by simultaneously showing infants a live and three-second delayed video of their own face or legs. The results confirm that infants prefer the delayed feedback of their own face. However, a specific preference is not observed when their own legs are displayed, indicating a developmental gap in the self-perception of body parts.
We examined the mechanisms of visual feature binding in humans and pigeons, two visually dominant vertebrates that use different neural substrates for feature processing. In Experiment 1, we examined how humans and pigeons bind color and line orientation. Subjects were trained to search for a target among distractors consisting of horizontal and vertical lines. In the feature condition, one of the target lines was a different color than the distractors. In the binding condition, the target and distractors were characterized by different combinations of colors and orientations. Both species located the target faster under the feature condition compared with the binding condition, suggesting that binding requires focal attention in both species. In Experiment 2, we examined the effects of spatial separation on visual feature binding. The target and distractors consisted of two horizontally aligned colored lines. The distance between the two lines had little effect on target localization in humans, whereas the process was hampered in pigeons. These results may reflect differences in the neural substrates of these species.