Kazufumi Omura

Emotional conflict and neuroticism: personality-dependent activation in the amygdala and subgenual anterior cingulate.

The amygdala and subgenual anterior cingulate (AC) have been associated with anxiety and mood disorders, for which trait neuroticism is a risk factor. Prior work has not related individual differences in amygdala or subgenual AC activation with neuroticism. Functional magnetic resonance imaging was used to investigate changes in blood oxygen level-dependent signal within the amygdala and subgenual AC associated with trait neuroticism in a nonclinical sample of 36 volunteers during an emotional conflict task. Neuroticism correlated positively with amygdala and subgenual AC activation during trials of high emotional conflict, compared with trials of low emotional conflict. The subscale of neuroticism that reflected the anxious form of neuroticism (N1) explained a greater proportion of variance within the observed clusters than the subscale of neuroticism that reflected the depressive form of neuroticism (N3). Using a task that is sensitive to individual differences in the detection of emotional conflict, the authors have provided a neural correlate of the link between neuroticism and anxiety and mood disorders. This effect was driven to a greater extent by the anxious relative to the depressive characteristics of neuroticism and may constitute vulnerability markers for anxiety-related disorders.

Interference produced by emotional conflict associated with anterior cingulate activation

The anterior cingulate cortex (ACC) is involved in cognition and emotion. In the classic Stroop task, presentation of stimuli that are in response conflict with one another produces activation in the caudal ACC. In the emotional Stroop task, presentation of emotionally salient stimuli produces activation in the rostral ACC. Presentation of stimuli that are emotionally conflicting should activate the caudal ACC; stimuli that are emotionally salient should activate the rostral ACC. We tested this prediction using functional magnetic resonance imaging while subjects made emotional valence judgments of words overlaid on emotional faces (word-face Stroop task). Emotionally incongruent pairs were responded to more slowly than emotionally congruent pairs. Emotionally incongruent trials were associated with increased activation within the caudal ACC, whereas no ACC activation was found in response to emotional saliency. These results support the conflict-monitoring model of caudal ACC and extend this function to conflict within the domain of emotional stimuli.

Functional connectivity with the anterior cingulate is associated with extraversion during the emotional Stroop task

Abstract Previous research has investigated the association of personality traits with brain activation in response to emotional stimuli. Our current research efforts are directed at understanding the temporal dynamics of networks of structures associated with particular personality traits, and gain insights into the functional contributions of more narrowly defined trait-facets that comprise these personality traits. To begin this process, we conducted a functional magnetic resonance imaging (fMRI) study using an emotional attention task (emotional Stroop paradigm) and addressed the question whether individual differences in extraversion and its lower-level facets were associated with differences in activation, and in functional connectivity, of the anterior cingulate (AC) cortex. We replicated our earlier finding that extraversion was associated with increased AC activation to positive, relative to neutral, word stimuli, but now show that distinct facets of extraversion can account for this association. When analyzing for functional connectivity, we found that greater extraversion across individuals was associated with greater functional connectivity between the AC and the inferior parietal lobule, and that this association could also be accounted for by distinct facets of extraversion. Our data suggest that extraversion and some of its lower-level facets are associated with individual differences across a network of structures believed to be critical in cognitive and affective processing.

Neural correlates of phoneme-to-grapheme conversion.

In writing to dictation, one mode of language processing is based on the knowledge of how to convert speech sounds to the corresponding letters, namely, phoneme-to-grapheme conversion (phonological mode). Little is known about the neural substrates of the phoneme-to-grapheme conversion. Our study aims to clarify the neural substrates of phoneme-to-grapheme conversion in writing to dictation using functional magnetic resonance imaging. We employed Japanese as the stimulus language because in Japanese, one phoneme is represented by one grapheme (kana) and vice versa. Functional magnetic resonance imaging revealed that the left premotor, extending into Brocas area was activated. The present results suggested that the frontal region is required for the conversion of phonemes to graphemes in writing to dictation.

Activation of insular cortex and subcortical regions related to feedback stimuli in a time estimation task: An fMRI study

We used functional magnetic resonance imaging to investigate brain activity related to motivational function of informative feedback stimuli in a time estimation task. In that task, subjects pressed a button as a response 3 s after a cue stimulus; a visual feedback stimulus was presented 2 s after the response. In a true feedback condition, subjects received true information (informative feedback) about their time-estimation performance. In the false feedback condition, the same visual signs were used, but they were presented randomly. Therefore, they were not related to actual performance. In the 20 subjects examined, higher hemodynamic responses were identified in the insular cortex, the thalamus, and the striatum by comparing the true feedback condition to the false feedback condition. The time estimation performance and subjective score on motivation were also markedly higher in the true feedback condition. The anterior insular cortex and striatal regions are known to be involved in motivational and reward processing. Therefore, the hemodynamic responses observed in this study suggest that the motivational function of the feedback information is a crucial factor for behavioral learning; it is considered that the informative feedback might serve as an implicit reward for humans.

LEARNING CHINESE CHARACTERS MAY IMPROVE VISUAL RECALL

From elementary through high school, Japanese children are required to memorize a large number of distinct visual forms, i.e., roughly 2,000 Chinese characters, and tremendous effort is expended in learning to read and write them. We hypothesized that early training in memorizing Chinese characters and the use of these characters in daily life shapes brain development and facilitates recall of visual forms in general, including geometrical figures in visual recall tests. To demonstrate whether the learning of Chinese character is correlated with specific aspects of memory, we administered the Wechsler Memory Scale–Revised (WMS–R) to a representative sample of the normal Japanese population (316 persons, 100% Japanese) and compared their scores with data previously obtained from a representative sample of the normal U.S. population (316 persons, 82.5% Caucasian). The WMS–R has 12 memory subtests, each measuring a different aspect of memory and includes two visual recall subtests (Visual Reproduction I and II). Compared to the Americans, the Japanese group obtained significantly higher scores on these two visual recall subtests in each of the six age groups tested (16 to 74 years old). Further, the scores of Japanese on the two visual recall subtests did not decline across age groups as much as scores for the U.S. group. Japanese also scored significantly higher on the Visual Memory Span subtest in three age groups.

Variance maps as a novel tool for localizing regions of interest in imaging studies of individual differences

Cognitive neuroimaging studies of individual differences seek to reveal brain mechanisms of cognition by associating intersubject variability in brain activation with other variables of interest, such as sex, personality trait, or mood state. The choice of a priori regions of interest (ROIs) raises problems, because the selection criterion is typically consistent activation across prior studies, suggesting little intersubject variability. Here, we introduce a novel approach for selecting regions that are defined on the basis of their variance characteristics, rather than on the basis of their location or because of theoretical expectations. These regions of variance (ROVs) constitute the search space with which to assess how much of the observed variance can be ascribed to specific variables of interest. We compare the ROI and ROV approaches by applying each to the same data set and suggest that the conjunction of both methods may yield the greatest likelihood of capturing the rich relation between brain and behavior, while limiting the search space for statistical analyses and minimizing false positive errors.

Simultaneous confirmatory factor analysis of the wechsler memory scale - revised for two standardization samples: a comparison of groups from Japan and the United States.

We employed a simultaneous confirmatory factor analysis to assess the hypothesized three-factor structure of the Wechsler Memory Scale – Revised (i.e., Attention/Concentration, Immediate Memory, Delayed Recall factors) in samples from Japan and the United States. The aim of the study was to provide a rigorous test of the hypothesis that the factor structure of the Wechsler Memory Scale – Revised is invariant across languages. We found configural invariance in two groups, that is, the same number of factors was found and the factor patterns were similar across the two samples. Our results tended to support the potential utility of the Wechsler Memory Scale – Revised in the analysis of the Japanese population, and the present findings appeared to be consistent with the contention that the Wechsler Memory Scale – Revised represents universal dimensions of memory. However, the factor patterns were slightly different between the two groups in the visual recall tests. The slight difference of the factor patterns may be caused with linguistic differences and/or differences among neural substrates in the brain associated with each group.