Published papers

Background: Emotional information is frequently processed below the level of consciousness, where subcortical regions of the brain are thought to play an important role. In the absence of conscious visual experience, patients with visual cortex damage discriminate the valence of emotional expression. Even in healthy individuals, a subliminal mechanism can be utilized to compensate for a functional decline in visual cognition of various causes such as strong sleepiness. In this study, sleep deprivation was simulated in healthy individuals to investigate functional alterations in the subliminal processing of emotional information caused by reduced conscious visual cognition and attention due to an increase in subjective sleepiness. Fourteen healthy adult men participated in a within-subject crossover study consisting of a 5-day session of sleep debt (SD, 4-h sleep) and a 5-day session of sleep control (SC, 8-h sleep). On the last day of each session, participants performed an emotional face-viewing task that included backward masking of nonconscious presentations during magnetic resonance scanning. Results: Finally, data from eleven participants who were unaware of nonconscious face presentations were analyzed. In fear contrasts, subjective sleepiness was significantly positively correlated with activity in the amygdala, ventromedial prefrontal cortex, hippocampus, and insular cortex, and was significantly negatively correlated with the secondary and tertiary visual areas and the fusiform face area. In fear-neutral contrasts, subjective sleepiness was significantly positively correlated with activity of the bilateral amygdala. Further, changes in subjective sleepiness (the difference between the SC and SD sessions) were correlated with both changes in amygdala activity and functional connectivity between the amygdala and superior colliculus in response to subliminal fearful faces.Conclusion: Sleepiness induced functional decline in the brain areas involved in conscious visual cognition of facial expressions, but also enhanced subliminal emotional processing via superior colliculus as represented by activity in the amygdala. These findings suggest that an evolutionally old and auxiliary subliminal hazard perception system is activated as a compensatory mechanism when conscious visual cognition is impaired. In addition, enhancement of subliminal emotional processing might cause involuntary emotional instability during sleep debt through changes in emotional response to or emotional evaluation of external stimuli.

Because of unique linguistic characteristics, the prevalence rate of developmental dyslexia is relatively low in the Japanese language. Paradoxically, Japanese children have serious difficulty analysing phonological processes when they have dyslexia. Neurobiological deficits in Japanese dyslexia remain unclear and need to be identified, and may lead to better understanding of the commonality and diversity in the disorder among different linguistic systems. The present study investigated brain activity that underlies deficits in phonological awareness in Japanese dyslexic children using functional magnetic resonance imaging. We developed and conducted a phonological manipulation task to extract phonological processing skills and to minimize the influence of auditory working memory on healthy adults, typically developing children, and dyslexic children. Current experiments revealed that several brain regions participated in manipulating the phonological information including left inferior and middle frontal gyrus, left superior temporal gyrus, and bilateral basal ganglia. Moreover, dyslexic children showed altered activity in two brain regions. They showed hyperactivity in the basal ganglia compared with the two other groups, which reflects inefficient phonological processing. Hypoactivity in the left superior temporal gyrus was also found, suggesting difficulty in composing and processing phonological information. The altered brain activity shares similarity with those of dyslexic children in countries speaking alphabetical languages, but disparity also occurs between these two populations. These are initial findings concerning the neurobiological impairments in dyslexic Japanese children.

Physiological bodily states play an important role in affective experiences. This study investigated whether the neural processing of internal body state (interoception) is associated with empathy, the understanding of the affective states of others. We used the 'heartbeat-evoked potential' (HEP), a surface electroencephalography (EEG) pattern, as a neural index of interoceptive processing. The HEP is contingent on the most prominent peak (R-wave) of the electrocardiogram (ECG) and is thought to reflect cortical processing of cardiac afferent input. Twenty-one healthy adults performed empathy and control tasks while EEG and ECG were recorded, where they made judgments based on either the affective or physical aspects of images of human eyes. HEP, ECG and heart rate in each task block were calculated and compared. Results showed that cardiac activity was not significantly different between tasks. In contrast, HEP showed a significant task difference, exhibited as an increased negativity during the empathy task over frontocentral sites at a latency of approximately 250-430. ms. Furthermore, a self-reported measure of empathy was associated with mean HEP amplitude during the period of task-related differentiation. These results suggest that afferent feedback from visceral activity may contribute to inferences about the affective state of others.

Background: The Levels of Emotional Awareness Scale (LEAS) was developed to assess five levels of emotional awareness: bodily sensations, action tendencies, single emotions, blends of emotion, and combinations of blends. It is a paper and pencil performance questionnaire that presents 20 emotion-evoking scenes. We developed a Japanese version of the LEAS (LEAS-J), and its reliability and validity were examined.Methods: The LEAS-J level was independently assessed by two researchers who scored each response according to the LEAS scoring manual. High inter-rater reliability and internal consistency were obtained for the LEAS-J. Measures were socioeconomic status, LEAS-J, Toronto Alexithymia Scale-20 (TAS-20), Interpersonal Reactivity Index (IRI), and NEO Five-Factor Inventory (NEO-FFI). TAS-20, IRI and NEO-FFI were the measures used to explore the construct validity of LEAS-J, as it was predicted that higher scores on the LEAS-J would be related to fewer alexithymic features, greater empathetic ability, and a greater sense of cooperation with others. Questionnaires were completed by 344 university students.Results: The criterion-referenced validity was determined: a significant negative relationship was found with the externally-oriented thinking scores of TAS-20, and positive relationships were found with fantasy, perspective taking, and empathic concern on IRI and with extraversion, openness to experience, and agreeableness on NEO-FFI.Conclusions: Consistent with our expectations, the findings provide evidence that the LEAS-J has good reliability and validity. In addition, women had significantly higher scores than men on LEAS-J, showing that the gender difference identified in the original LEAS was cross-culturally consistent.

Given the results of studies using the Iowa Gambling Task (IGT), emotion-based sensitivity to an anticipated outcome of one's own behavior has been suggested to be a significant factor in making advantageous decisions. Hypotheses-testing in performing IGT is essential for learning correct rules and elicits autonomic reactivity. In this study, participants were asked to concentrate on hypothesis-testing to learn undisclosed rules in the task which framework was similar to the IGT, rather than maximizing monetary reward. The amplitudes of skin conductance responses (SCRs) prior to card selection and following feedback were attenuated as participants came to accurately comprehend the task rules. The attenuation of SCRs resulted from reduced motivation to continue the hypotheses-testing. Our findings provide some evidence that observed autonomic responses partially reflect emotional reactions associated with the hypothesis-testing.