Biomedical subjects

Jun'ichi Katayama

Publications and source records attributed to Jun'ichi Katayama.

10 recordsLinked to original sources

PubMed2006

Stimulus context determines whether non-target stimuli are processed as task-relevant or distractor information.

OBJECTIVE: The P300 event-related brain potential (ERP) was elicited using a visual three-stimulus oddball paradigm (standard 0.70, target 0.15, non-target 0.15) to examine how target/standard stimulus context affects non-target processing. METHODS: Target/standard discrimination difficulty (easy or difficult) and non-target /target similarity (similar or dissimilar) were manipulated orthogonally. Participants (N=13) were instructed to respond to each infrequent target stimulus by pressing a button. RESULTS: Target stimuli in all task conditions elicited P3b, which was affected only by the difficulty of target/standard discrimination. When target/standard discrimination was easy, the amplitude of non-target P3 was larger for similar than for dissimilar non-target. In contrast, when target/standard discrimination was difficult, non-target stimuli elicited P3a, the amplitude of which was larger for dissimilar than for similar non-target. Thus, the P300 component for non-target stimuli and the pattern of the effect of target similarity on each P300 component varied as a function of the target/standard stimulus context. CONCLUSIONS: The target/standard stimulus context influences the attentional set for stimulus processing such that it determines whether non-target stimuli are processed as task-relevant or distractor information. SIGNIFICANCE: The present results are important for understanding the mechanism of cognitive modification in non-target processing.

Adult↗

PubMed2006

Severity of AD/HD symptoms and efficiency of attentional resource allocation.

This study investigated the mechanism that underlies the inefficient allocation of attentional resources in Attention-Deficit/Hyperactivity Disorder (AD/HD). The P300 event-related brain potential (ERP) was elicited from 24 healthy adults using a visual three-stimulus oddball paradigm (standard, 70%; target, 15%; non-target, 15%) and the degree of their AD/HD symptoms was assessed by using AD/HD symptom scales. Target stimulus was a circle and standard stimulus was an "X". Two task conditions were defined according to the non-target stimulus type (typical or novel): a triangle for the typical condition and colored non-repetitive novel stimuli for the novel condition. In both conditions, target and non-target elicited P300s. A ratio of non-target P300 to target P300 amplitude was used to assess the efficiency of attentional resource allocation; low ratio indicates the efficient allocation of attentional resource. The correlation analysis revealed a strong positive correlation between the AD/HD symptom score and the P300 amplitude ratio in the typical condition (r=.80), while only a weak positive correlation was observed in the novel condition (r=.23). The present study found that the commonality of task-relevant and task-irrelevant information, rather than the stimulus novelty of task-irrelevant information, induces the inefficient allocation of attentional resources in AD/HD.

Adult↗

PubMed2006

An ERP study of visual change detection: effects of magnitude of spatial frequency changes on the change-related posterior positivity.

In event-related brain potential (ERP) studies using a visual S1-S2 matching task, change stimuli elicit a posterior positivity at around 100-200 ms. In the present study, we investigated the effects of magnitude of spatial frequency changes on change-related positivity. Each trial consisted of two sequentially presented stimuli (S1-S2), where S2 was either (1) the same as S1 (i.e., NO-change, p=.40), (2) different from S1 in spatial frequency only (SF-change, .40), (3) different in orientation only (OR-change, .10), or (4) different in both spatial frequency and orientation (BOTH-change, .10). Further, three magnitude conditions (Large, Medium, and Small) were used to examine the effect of the magnitude of the spatial frequency change. Participant's (N=12) task was to respond to S2 with a change in orientation (from vertical to horizontal, or from horizontal to vertical) regardless of the spatial frequency of the stimulus. Changes in the spatial frequency elicited change-related positivity at a latency range of about 120-180 ms, which was followed by a central negativity (N270) and a late positive component (LPC). The amplitude of the change-related positivity tends to be enhanced as the magnitude of the change is increased. These results support the notion that the change-related positivity reflects memory-based change detection in the human visual system.

Adult↗

PubMed2006

Probability-independent and -dependent ERPs reflecting visual change detection.

In ERP studies, two posterior components with different polarities have been identified as ERP correlates of visual change detection. To compare these components in terms of sensitivity to the preceding stimulus sequence, two peripheral stimuli of different colors (red and blue) were presented with equal (50:50) or different probabilities (20:80 or 80:20), while 12 participants performed shape discrimination at a central location. A posterior positivity at around 90-140 ms was observed with similar amplitude to all stimuli immediately preceded by a different stimulus. In contrast, a posterior negativity at around 140-180 ms was observed to increase in amplitude with increasing number of preceding different stimuli. These results suggest the existence of probability-independent and -dependent change processing in the human visual system. The functional significance is discussed in terms of memory-based comparison and stimulus-specific refractoriness.

Adult↗

PubMed2005

Neural correlates of pre-attentive and attentive processing of visual changes.

To identify electrophysiological correlates of pre-attentive and attentive processing of visual changes, we compared event-related brain potentials in response to color changes at attended and unattended spatial locations using a visual S1-S2 matching task. The results showed that compared to no change, change stimuli elicited occipito-temporal positivity at around 100-160 ms (change-related positivity) and subsequent central negativity at around 220-300 ms (N270). Change-related positivity was observed in response to changes at both attended and unattended locations, while N270 was observed only when attention was directed to the location of the changes. These results suggest that change-related positivity reflects the pre-attentive processing of visual changes and N270 reflects the attentive processing of visual changes in the human brain.

Adult↗

PubMed2005

An unnecessary response is detected faster than an insufficient response.

Error-related negativity is an event-related potential component that is observed when participants make errors and reflects action monitoring that involves error detection. In this study, an over-response error (responding with both hands when participants were asked to respond with only one hand) and an under-response error (responding with one hand when asked to respond with both hands) were assessed by the characteristics of the error-related negativity during a modified Eriksen flankers task. The results indicated that a bimanual response error also elicited the error-related negativity, and that the onset latency of the error-related negativity was shorter for an over-response error than for an under-response error. Thus, these results suggest that the error-detection process is more sensitive to an unnecessary response than to an insufficient response.

Adult↗

PubMed2005

Independent processing of visual stimulus changes in ventral and dorsal stream features indexed by an early positive difference in event-related brain potentials.

In event-related brain potential (ERP) studies of brain activity using a visual S1-S2 matching task, change stimuli elicit a posterior positive component with a latency of 100-200 ms. To elucidate the hierarchical organization of the processing of a visual stimulus change based on multiple stimulus features, ERPs were recorded in 12 participants performing an S1-S2 matching task with stimuli defined by color (mediated by the ventral stream) and motion direction (mediated by the dorsal stream). Each trial consisted of two sequentially presented stimuli (S1-S2), where S2 was either (1) the same as S1 (i.e., no change), (2) different from S1 in color only (color change), (3) different in motion direction only (motion direction change), or (4) different in both color and motion direction (color-motion direction change). These trials were presented in random order with equal probability, and the participants were asked to respond to one of these trials in separate blocks. Relative to the no-change stimulus, the three types of change stimuli elicited posterior positivities. The scalp-topography of change positivities differed according to the feature changed. In addition, the amplitude and scalp-topography of change positivities in response to a conjunction change were the respective sums of those in response to changes in the corresponding single features. These results suggest that the change detection system reflected by the change positivity is separate for each feature dimension, and these operate independently.

Adult↗

PubMed2005

Positive difference in ERPs reflects independent processing of visual changes.

To elucidate the nature of the processing of visual stimulus changes, ERPs were recorded while 12 participants performed an S1-S2 matching task with multifeature stimuli. Each trial consisted of two sequentially presented stimuli (S1-S2), where S2 was either the same as S1, different from S1 only in color, different only in shape, or different in both color and shape. The four trial types were presented in random order with equal probability, and participants responded to one of these types in separate blocks. Relative to the no-change stimuli, the change stimuli elicited posterior positivity with different topography according to changing features ranging from 100 to 180 ms in all tasks. The amplitude and topography of the positivity in response to the both changes were the respective sums of those to changes in the corresponding single features. These results suggest that a feature-specific change detection system exists in the human visual system.

Adult↗

PubMed2004

Face-specific N170 component is modulated by facial expressional change.

We examined processing of change in facial expression. Event-related brain potentials (ERPs) were elicited by successive presentation of two different faces without interval. Smile faces were preceded by either a neutral face of the same person, a smile face of a different person, or a neutral face of a different person, which generated expressional, individual, or both expressional and individual change, respectively. For the preceding faces, there were no differences in face-specific N170. In contrast, the second faces elicited a larger N170 for expressional change relative to individual or both changes, which indicates that facial expression was processed in the early stage of face processing in the posterior temporal region, when they are presented in change context.

Adult↗

PubMed2003

Attending to a location in three-dimensional space modulates early ERPs.

It has been reported that attending to a particular location can modulate incoming sensory signals, as reflected by the stimulus-evoked P1 and N1 components of the visual event-related potential (ERPs) in a two-dimensional (2D) display [Attention, Space, and Action: Studies in Cognitive Neuroscience, Oxford University Press, New York, 1999, p. 31]. In contrast, in this study we examined the effect of attention in 3D space using a stereoscopic display. Stimuli were presented randomly, one at a time, in an orthogonal combination of two depths (near, far) and two 2D locations (left, right) relative to the fixation point. The task was to attend selectively to one of these four positions and to respond to a target stimulus defined by shape in the attended 3D location. The effect of 2D location selection on the P1 amplitude was greater for stimuli in the near than the far depth plane, and the amplitude of N1 increased in response to stimuli in the attended combination of 2D location and depth. These results suggest that the effect of early spatial selection on the visual ERP is not simply based on retinotopic organization of the visual field, but also on intermediate stages that construct a 3D spatial representation of the external world.

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