Makoto Miyatani

The N400 component of event-related potentials in schizophrenic patients: a preliminary study.

ERPs were recorded during a word recognition task to investigate cognitive dysfunction in schizophrenia. Thirteen medicated schizophrenics and 26 normal controls were tested. In each trial a pair of stimuli, S1 (a word) and S2 (a word or a non-word), were presented. The subjects were required to discriminate between a word and a non-word for S2 (lexical decision task). In a related (R) condition, S2 was the antonym of S1 (e.g., brother-sister); in an unrelated (U) condition, S1 and S2 were semantically unrelated (e.g., brother-drive); in the non-word (N) condition, S2 was a non-word (e.g., brother-grofe). The ERPs for S2 were analyzed, and the contextual effects on the ERPs for S2 observed for both the patients and controls. For both groups, in the U and N conditions S2 elicited a large negative-trending deflection (N370). In contrast, in the R condition it elicited only a small negative-trending notch. There was no difference in the amplitude of N370 between the groups, but its latency was more prolonged or its wave shape more extended for the schizophrenics than for the controls. The N400 amplitude is concluded to remain unchanged in schizophrenics.

Compensatory cortical activation during performance of an attention task by patients with diffuse axonal injury: a functional magnetic resonance imaging study

Objective: To determine how cortical compensation occurs in higher cognitive systems during the recovery phase of diffuse axonal injury (DAI). Design: 12 right-handed patients with a magnetic resonance imaging (MRI) lesion pattern compatible with pure DAI were identified. Pure DAI was defined as finding of traumatic microbleeds on T2*-weighted gradient-echo images in the absence of otherwise traumatic or non-traumatic MRI abnormalities. 12 matched healthy controls were also enrolled. Functional magnetic resonance imaging (fMRI) was used to assess brain activation during a working memory test (Paced Visual Serial Attention Test (PVSAT)). Results: No significant group differences were observed in reaction times for the PVSAT. Although patients with pure DAI committed a few errors during the PVSAT, controls respond correctly to each probe. Controls showed activations in the left frontal gyrus, left parietal gyrus and right inferior parietal gyrus. Patients with pure DAI showed activations in the left inferior frontal gyrus, right inferior frontal gyrus and right middle frontal gyrus. Between-group analysis of the PVSAT task showed significantly greater activation of the right inferior frontal gyrus (BA 45) and right middle frontal gyrus (BA 9) in patient with pure DAI versus controls. Conclusions: Patients with pure DAI require compensatory activation of the contralateral (right) prefrontal region to carry out activities similar to healthy controls. These findings provide further evidence for the adaptive capacity of neuronal systems and brain plasticity during the recovery stages of DAI.

ERPs in schizophrenic patients during word recognition task and reaction times

Event-related brain potentials (ERPs) were recorded in 28 schizophrenic patients and 26 healthy controls during a word recognition task. In each trial, stimuli consisting of S1 (word) and S2 (word or non-word) were presented. The subjects were required to indicate whether S2 was a word or a non-word by pressing buttons. For both groups, a clear N370 was elicited by S2 which were non-word or semantically unrelated to its S1. The N370 amplitude did not differ between the groups. The schizophrenics responded more slowly than the controls, and the latencies of P200 and N370 were longer for patients than for controls. However, these latencies did not differ between the groups when their reaction times were matched.

Self-Knowledge Reduces Conflict by Biasing One of Plural Possible Answers

The authors investigated whether self-knowledge has a function to reduce conflict by biasing one of two choices during occupational choice (e.g., Which occupation do you think you could do better?—dancer or chemist). In the three experiments, event-related brain potentials were recorded. Experiment 1 revealed that the amplitude of the conflict-related negativity (CRN) reflects strength of conflict during occupational choice. Results of Experiment 2 demonstrated that the CRN amplitude during occupational choice was smaller when self-knowledge was activated than when other-knowledge was activated. Experiment 3 showed that the CRN amplitude during occupational choice was decreased more when self-knowledge that biases one choice of occupation was activated than when self-knowledge that does not bias was activated. These results suggest that self-knowledge reduces conflict by biasing one of multiple choices in situations where two or more possible correct answers can be given.

Activation of Self-Knowledge Reduces Conflict During Occupational Choice: An ERP Study

We investigated whether the activation of self-knowledge reduces conflict during occupational choice, which can elicit many correct answers. Conflict was measured via event-related brain potentials (ERPs). Results of this study showed that activation of self-knowledge reduces conflict during occupational choice. Our results suggest that, in a situation in which two or more possible correct answers exist, people use self-knowledge as a benchmark to reduce conflict by biasing either choice of behavior.

Quantitative Relation between Conflict and Response Inhibition in the Flanker Task

The 2001 conflict monitoring hypothesis of Botvinick and colleagues posits that the amount of conflict raised by incongruent stimuli in a flanker task affects subsequent cognitive control, such as response inhibition. The present experiment yielded empirical evidence of the quantitative relation between conflict and response inhibition. Participants judged the direction of a target arrow flanked by distractor arrows presented above and below the target. The amount of conflict was manipulated by varying the distance between the target and the directional distractors. Analysis showed that response times were longer for incongruent trials than for congruent trials, and response times on incongruent trials were longer for the small distance than for the large distance conditions. In addition, the response times in congruent trials became longer as the amount of conflict in the preceding trial increased. These results are consistent with Botvinick, et al.s hypothesis that the conflict-detection mechanism determines the amount of response inhibition depending on the amount of conflict. Responses on incongruent trials were faster and more accurate when the preceding trial was incongruent than when it was congruent, and the size of this response facilitation was not influenced by the amount of conflict. These results suggest that the conflict detection mechanism modulates the subsequent behaviors by two forms of control which are differently affected by the amount of conflict.

Brain activations in errorless and errorful learning in patients with diffuse axonal injury: A functional MRI study

Primary objective: Errorless learning has been reported to be effective in the rehabilitation of patients with impaired cognitive functions following brain injury. This study compared brain activations in errorless learning (EL) and errorful learning (EF) in patients with diffuse axonal injury (DAI) using a functional magnetic resonance imaging (fMRI). Methods and procedures: The participants were 13 patients with DAI. Thirteen healthy individuals were evaluated as a control group. The participants learned words under the EL and EF conditions in advance and performed the recognition task during fMRI scanning. Main outcomes and results: EL in the control group was significantly faster than EF (p = 0.005), but not in the DAI group. EL in the DAI group scored significantly higher than EF (p = 0.026). An fMRI showed significant activations in the posterior cingulate gyrus (BA 31) and precuneus (BA 7) in the control group when EF > EL, but in the precuneus (BA 7, 31) and bilateral inferior parietal lobules (BA 39, 40) in the DAI group. Conclusions: These results indicate the disadvantage of EF and advantage of EL to DAI patients. The findings also reflect brain plasticity in patients with DAI in the chronic phase.

The Effect of Informative and Uninformative Cueing of Attention on Feature Integration

Abstract In the present study, the authors observed the effect of informative and uninformative attentional cueing on visual search for targets that were defined by a simple feature or by conjunctions of features. Three different types of attentional cueing were tested in three experiments: peripheral informative cueing, peripheral uninformative cueing, and central informative cueing. Participants showed a greater effect of cueing in detecting a conjunction of features than in detecting unique features only when attention was oriented by either peripheral or central informative cueing. This differential cueing effect was not observed when attention was oriented by peripheral uninformative cueing. The results suggest that voluntarily oriented attention plays a more important role in feature integration than automatically oriented attention does. The results also pose limits on the generalizability of K. A. Briands (1998) proposal regarding the role of automatically oriented attention in feature integration.

Self-reference in elaborative processing of desirability of trait adjectives.

We investigated whether the desirability of trait adjectives was elaboratively processed during self-reference tasks (Exp. 1–1, 1–2) and whether desirability information played a role in memory processes in self-reference tasks (Exp. 2). In Exp. 1–1, 14 participants performed a series of initial tasks and target tasks, which were self-reference, evaluative, or semantic. Responses on the evaluating target task were faster when the initial task was self-reference rather than semantic. Exp. 1–2 demonstrated that information relevant to the evaluative task did not facilitate the process of performing an other-reference task. Although there was no evidence that desirability information had a role in the self-reference effect in Exp. 2, desirability of trait adjectives was specifically processed during self-reference tasks.

Altruistic People Show No Self-Reference Effect in Memory

ABSTRACT The self-reference effect (SRE), by which encoding of information is done in a self-referential manner (e.g., “Does the word describe you?”), enhances subsequent memory performance. It is thought to reflect that self-reference is a highly practiced task in everyday life. Accordingly, it is expected that the types of tasks that produce memory enhancement vary according to individual differences of past experiences. On the basis of neuroimaging studies, we hypothesized that social desirability reference (“Is this word socially desirable?”) produces memory enhancement as with SRE in people who have chosen altruistic behavior frequently. Participants processed trait adjectives in relation to themselves, social desirability, and meaning. Then they performed a free recall task. The self-report altruism scale was used to assess the frequency of past altruistic behavior. Consistent with our prediction, the social desirability reference yielded the best retention in the high-altruism group. SRE was observed only in the low-altruism group.