Jun'ichi Katayama

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.

Neural correlates of preattentive and attentive processing of visual changes

To identify electrophysiological correlates of preattentive 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 preattentive processing of visual changes and N270 reflects the attentive processing of visual changes in the human brain.

Somatosensory P2 reflects resource allocation in a game task: Assessment with an irrelevant probe technique using electrical probe stimuli to shoulders

The present study investigated whether event-related brain potentials (ERPs) elicited by task irrelevant somatosensory stimuli to the shoulders reflect the amount of processing resources allocated to a game task. In the experiment, electrical stimuli were presented to the right (or left) shoulder with a high probability (80%) and to the other shoulder with a low probability (20%) while participants were performing a driving simulation game. The deviant low-probability stimuli elicited somatosensory P2, and this P2 amplitude decreased when the task was difficult. The results show that the ERPs for somatosensory stimuli to the shoulders can reflect the amount of resources deployed even when the stimuli are ignored. This is a useful method for the evaluation of mental workloads in complex circumstances because it does not interfere with inputs of auditory or visual information or operations using the limbs.

Sentence verification and event-related brain potentials.

The purpose of this study was to examine whether the decision process affected scalp recorded event-related brain potentials (ERPs). ERPs were recorded while 10 subjects evaluated the veracity of four types of Japanese sentences; true-affirmative (TA), true-negative (TN), false-affirmative (FA), and false-negative (FN). Each sentence was presented visually, one word at a time in the following order: Subject (S); object (O); and verb (V). This order of words, which is normal in Japanese grammar, allowed the ERP waveforms associated with semantic mismatch between the S and O occurring in the middle of the sentence to be separated from those elicited by the decision concerning the sentences truth or falsity occurring at the end of the sentence. Semantic mismatch was associated with a negative component (N310) following the O-word. In addition, P3s were elicited by sentence final words. Affirmative sentences elicited larger P3s than did negative sentences, and true sentences elicited earlier P3s than did false sentences. P3s were smaller in amplitude when they followed a mismatch between the S and O words. The result suggested that by using Japanese sentences, it may be possible to examine sentence-level rather than word-level processes.

Outcome evaluations in group decision making using the majority rule: An electrophysiological study

Event-related brain potential (ERP) reflecting outcome evaluation is called feedback-related negativity (FRN). The present study examined the evaluative processes for two different types of outcomes by recording ERPs from three participants during a group decision task. First, we examined the evaluative processing of outcomes associated with group decisions using the majority rule. Second, we investigated whether the majority rule influenced the evaluation of conflicts related to individual opinions among group members. We found that FRN for monetary loss associated with the group decision was reduced when the participants opinion was in the minority. In addition, conflict of opinions among group members elicited FRN-like negativity, and greater amplitudes were observed when the participants opinion was in the minority. The present results suggested that the majority rule can modulate outcome evaluations in group decision making.

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. However, in the simple condition with low distraction, there was no difference in N1 between the groups. For all participants (n=52), the correlation between the scores for WMC and N1 peak amplitude was strong for distractors in the novel condition, whereas there was no relation in the simple condition. These results suggest that WMC can predict the interference control for a salient distractor at auditory gating even during a selective attention task.

Negative brain potentials elicited by an unexpected color patch or word

The purpose of this study was to examine whether a physical stimulus that deviates from a semantic context can elicit the N400 component of event-related brain potentials (ERPs). ERPs were recorded while 12 students judged the veracity of a simple statement (e.g., red/is not/blue) presented with the order of subject (S), object (O), and verb (V), which is normal in Japanese grammar. In one condition, S was a color patch and O was a word representing the color, while in the other condition, S was a color name and O was a patch. In both conditions, a late additional negative potential was elicited by the O stimulus when it was mismatched with S. In addition, the negativities elicited by the incongruous color patch and word had the same morphology and scalp distribution. The results indicate that not only a word but a physical stimulus which deviates from a semantic context can elicit the N400 component.

Neural correlates of error processing reflect individual differences in interoceptive sensitivity

Although self-monitoring is an important process for adaptive behaviors in multiple domains, the exact relationship among different internal monitoring systems is unclear. Here, we aimed to determine whether and how physiological monitoring (interoception) and behavioral monitoring (error processing) are related to each other. To this end we examined within-subject correlations among measures representing each function. Score on the heartbeat counting task (HCT) was used as a measure of interoceptive awareness. The amplitude of two event-related potentials (error-related negativity [ERN] and error-positivity [Pe]) elicited in error trials of a choice-reaction task (Simon task) were used as measures of error processing. The Simon task presented three types of stimuli (objects, faces showing disgust, and happy faces) to further examine how emotional context might affect inter-domain associations. Results showed that HCT score was robustly correlated with Pe amplitude (the later portion of error-related neural activity), irrespective of stimulus condition. In contrast, HCT score was correlated with ERN amplitude (the early component) only when participants were presented with disgust-faces as stimuli, which may have automatically elicited a physiological response. Behavioral data showed that HCT score was associated with the degree to which reaction times slowed after committing errors in the object condition. Cardiac activity measures indicated that vigilance level would not explain these correlations. These results suggest a relationship between physiological and behavioral monitoring. Furthermore, the degree to which behavioral monitoring relies on physiological monitoring appears to be flexible and depend on the situation.

Event-Related Brain Potentials to Nonwords and Semantically Different Words

The purpose of this study was to examine the nature of N2 component in event-related brain potentials (ERPs) which was associated with the deviation from the internal model of the semantic environment. Of the visually presented stimuli 60% were nouns belonging to the same semantic category (C), 20% belonged to other categories (NC), and the other 20% were nonwords (NW). 10 subjects were asked to detect NW and to press a key. The NW elicited central N2 with peak latency about 440 msec. and parietal P3 around 590 msec. Furthermore, smaller and later N2 peaked at about 480 msec. and distributed front-centrally, appeared in response to other categories. Differences of N2 in amplitudes and latencies may reflect differences of mismatches among nonwords, other categories, and the same semantic category.

Approach of visual stimuli modulates spatial expectations for subsequent somatosensory stimuli.

To examine how the approach of visual stimuli toward the body influences expectations regarding subsequent somatosensory stimuli, we recorded event-related brain potentials (ERPs; nose reference) during a simple reaction time to somatosensory stimuli task. Twelve participants were asked to place their arms on a desk, and three LEDs were placed between their arms at equal intervals. Electrical stimuli were presented to the left (or right) wrist at a high probability (80%) or to the opposite wrist at a low probability (20%). Each trial was composed of three visual stimuli followed by one electrical stimulus. In Experiment 1, the right, center, and left (or left, center, and right) LEDs were turned on sequentially toward the wrist to which the high probability somatosensory stimuli was presented (congruent condition), or the center LED were presented three times (neutral condition). Experiment 2 was composed of the congruent condition and the inverse of the congruent condition (incongruent condition). In both experiments, the reaction times to low probability stimuli were longer than those to high probability stimuli. Moreover, the low probability stimuli elicited a larger P3 amplitude than the high probability stimuli. In addition, the P3 amplitude was higher under the visual approach condition (i.e., the congruent condition in each experiment) than under the control condition (i.e., the neutral and incongruent conditions). Furthermore, no effect on the CNV amplitude before the somatosensory stimuli was found. These results suggest that visual stimuli directed toward the body induce an automatic spatial expectation for subsequent somatosensory stimuli.