Approach to impaired corollary discharge in patients with schizophrenia: An analysis of self-induced somatosensory evoked potentials and fields.

Background: Difficulty in distinguishing between self-generated actions and those generated by others is a core feature of schizophrenia. This is thought to be underpinned by the failure of corollary discharge. However, few studies have investigated these events using somatosensory evoked potentials (SEPs) and somatosensory evoked magnetic fields (SEFs).

Neural responses to feedback information produced by self-generated or other-generated decision-making and their impairment in schizophrenia.

Several studies of self-monitoring dysfunction in schizophrenia have focused on the sense of agency to motor action using behavioral and psychophysiological techniques. So far, no study has ever tried to investigate whether the sense of agency or causal attribution for external events produced by self-generated decision-making is abnormal in schizophrenia. The purpose of this study was to investigate neural responses to feedback information produced by self-generated or other-generated decision-making in a multiplayer gambling task using even-related potentials and electroencephalogram synchronization.

Attention that covers letters is necessary for the left-lateralization of an early print-tuned ERP in Japanese hiragana.

Extensive experience with reading develops expertise in acquiring information from print, and this is reflected in specific enhancement of the left-lateralized N170 component in event-related potentials. The N170 is generally considered to reflect visual/orthographic processing; while modulations of its left-lateralization related to phonological processes have also been indicated. However, in our previous study, N170-like response to Hiragana strings lacked left-lateralization when the stimuli were completely task-irrelevant in rapid-presentation sequences [Okumura et al.

Early print-tuned ERP response with minimal involvement of linguistic processing in Japanese Hiragana strings.

The act of reading leads to the development of specific neural responses for print, the most frequently reported of which is the left occipitotemporal N170 component of event-related potentials. However, it remains unclear whether this electrophysiological response solely involves print-tuned neural activities. The present study examined an early print-tuned event-related potential response with minimal involvement of linguistic processing in a nonalphabetic language.

Individuals with Asperger's disorder exhibit difficulty in switching attention from a local level to a global level.

The purpose of the present study was to determine whether individuals with Asperger's disorder exhibit difficulty in switching attention from a local level to a global level. Eleven participants with Asperger's disorder and 11 age- and gender-matched healthy controls performed a level-repetition switching task using Navon-type hierarchical stimuli. In both groups, level-repetition was beneficial at both levels.

Discrepancy of neural response between exogenous and endogenous task switching: an event-related potentials study.

Task switching is a well-known cognitive paradigm to explore task-set reconfiguration processes such as rule shifting. In particular, endogenous task switching is thought to differ qualitatively from stimulus-triggered exogenous task switching. However, no previous study has examined the neural substrate of endogenous task switching.

Working memory capacity affects the interference control of distractors at auditory gating.

It is important to understand the role of individual differences in working memory capacity (WMC). We investigated the relation between differences in WMC and N1 in event-related brain potentials as a measure of early selective attention for an auditory distractor in three-stimulus oddball tasks that required minimum memory. A high-WMC group (n=13) showed a smaller N1 in response to a distractor and target than did a low-WMC group (n=13) in the novel condition with high distraction.

Role of the prefrontal cortex in the cognitive control of reaching movements: near-infrared spectroscopy study.

To elucidate the role of the prefrontal cortex in cognitive control of reaching movements, by multichannel near-infrared spectroscopy we examine changes in oxygenated hemoglobin (oxy-Hb) as an indicator of changes in regional cerebral blood flow in the bilateral dorsolateral (DLPFC), ventrolateral prefrontal cortex (VLPFC), and frontopolar cortex (FPC) during a reaching task with normal visual feedback (a consistent task) and a reaching task with flipped horizontal visual feedback (an inconsistent task). Subjects first perform 12 trials of the consistent task, and then perform six blocks of the inconsistent task, each of which consists of six trials. During the consistent task, oxy-Hb is increased only in the right VLPFC.

Comprehension of degraded speech sounds with m-sequence modulation: an fMRI study.

In a recent electroencephalography (EEG) study (Takeichi et al., 2007a), we developed a new technique for assessing speech comprehension using speech degraded by m-sequence modulation and found a correlation peak with a 400-ms delay. This peak depended on the comprehensibility of the modulated speech sounds.

Underlying mechanisms of the P3a task-difficulty effect.

In three-stimulus oddball studies, even typical deviant stimuli elicited a large P3a event-related brain potential (ERP) when target/standard discrimination was difficult. To investigate the underlying mechanisms, the effects of task difficulty on early deviant-related ERPs were assessed. Four visual stimuli defined by an orthogonal combination of task-relevant size (nontarget 80%, target 20%) and task-irrelevant luminance (standard 80%, deviant 20%) were presented randomly, where two task difficulties (easy, difficult) were defined by target/nontarget discriminability.

Effects of feature and spatial attention on visual change detection.

In event-related brain potential studies using a visual S1-S2 matching task, stimulus changes elicit change-related positivity, which reflects the detection of visual changes. To investigate the effects of attention on change detection, we tested the elicitation of change-related positivity in response to changes in color and spatial frequency under three attention conditions: (i) changes in an unattended feature at an attended location, (ii) in an attended feature at an unattended location, and (iii) in an unattended feature at an unattended location. The results suggest that stimulus changes can be detected even when both feature and spatial attention are withdrawn, but change detection can also be inhibited, which might be because of biased-competition determined by the combination of feature and spatial attention conditions.

Involvement of memory-comparison-based change detection in visual distraction.

The involvement of memory-comparison-based change detection in visual distraction was elucidated. Not only luminance increments that engaged memory-comparison-based change detection and refractoriness-based rareness detection but also luminance decrements that engaged only memory-comparison-based change detection caused behavioral distraction, which was mirrored by a posterior negativity (240-260 ms, posterior N2) and a broad positivity (420-460 ms, P3a) that reflected attentional capture. Preceding these effects, luminance increments elicited a posterior positivity (100-120 ms, change-related positivity) and a posterior negativity (120-140 ms, change-related negativity), whereas luminance decrements elicited only a posterior positivity (160-180 ms, change-related positivity).

Attention switching function of memory-comparison-based change detection system in the visual modality.

To elucidate the attention switching function of a memory-comparison-based change detection system in the visual modality, the effects of task-irrelevant infrequent stimulus-size decrements that engaged memory-comparison-based change detection as well as stimulus-size increments that engaged memory-comparison-based change detection and refractoriness-based rareness detection on behavioral and event-related brain potential (ERP) measures were assessed using the distraction paradigm. Both size increments and size decrements caused distraction in forced-choice task performance, which was mirrored by a posterior negativity (peaking at around 240-260 ms, posterior N2) and a broad positivity (420-460 ms, P3a) that reflected attentional capture. Preceding these effects, size increments elicited a posterior negativity (120-140 ms, change-related negativity), while size decrements elicited a posterior positivity (140-160 ms, change-related positivity) and an anterior positivity (160-180 ms, frontal positivity).

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.

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.

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.

Discrepancy between feedback negativity and subjective evaluation in gambling.

Feedback negativity is a negative event-related potential elicited by feedback indicating incorrect performance or monetary loss. It is unclear whether this negativity is elicited by neutral feedback (e.g.

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.

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.