Cortico-striatal-thalamic loop as a neural correlate of neuroticism in the mind-body interface.

OBJECTIVE: Although brain structural studies have demonstrated the neural correlates of neuroticism, the outcomes are not easily identified because of the various possible brain regions involved, low statistical power (low number of subjects), and brain structural measures available, such as mean diffusivity (MD), which are more suitable than standard regional measures of grey and white-matter volume (rGMV, rWMV) and fractional anisotropy (FA). We hypothesized that neuroticism neural correlates could be detected by MD and differentially identified using other measures. We aimed to visualize the neural correlates of neuroticism. METHODS: A voxel-by-voxel regression analysis was performed using the MD, rGMV, rWMV, or FA value as the dependent variable and with neuroticism scores based on the NEO-FFI and its confounding factors as independent variables in 1207 (693 men and 514 women; age, 20.7 ± 1.8, 18-27 years), non-clinical students in a cross-sectional study. RESULTS: MD in the cortico- (orbitofrontal cortex, anterior cingulate cortex, and posterior insula) striatal- (caudate and putamen) thalamic loop regions, including the right posterior limb of the internal capsule, were positively associated with neuroticism using the threshold-free cluster enhancement method with a family-wise error-corrected threshold of P < 0.0125 (0.05/4, Bonferroni correction for four types of MRI data [MD, rGMV, rWMV, and FA]) at the whole-brain level. CONCLUSIONS: An increased MD has generally been associated with reduced neural tissues and possibly area function. Accordingly, this finding helps elucidate the mechanism of somatization in neuroticism because the regions related to neuroticism are considered neural correlates of somatoform disorders.

Effects of training of shadowing and reading aloud of second language on working memory and neural systems.

Shadowing and reading aloud both involve multiple complex cognitive processes, and both are considered effective methods for second-language learning. The working memory system, particularly the phonological loop, has been suggested to be involved in shadowing and reading aloud. The purpose of this study was to investigate the effects of a 4-week intensive adaptive training including shadowing and reading aloud of second language on working-memory capacity, regional gray matter volume (rGMV), and functional activation related to the n-back working-memory task in young adults. The results showed that compared with the training groups without speaking (listening to compressed speech and active control involving the second language), the training groups with speaking (shadowing and reading aloud) showed a tendency for greater test-retest increases in digit-span scores, and significantly greater test-retest decreases in N-back task reaction time (increase in working memory performance). Imaging analyses revealed compared with the active control group, shadowing group exhibited decreases in rGMV and brain activity during the working memory task (2-back task), in the left cerebellum and reading group exhibited decreases in them in the right anterior insula. These regions are parts of the phonological loop, suggesting the presence of training-induced neural plasticity in these neurocognitive mechanisms.

Mean diffusivity related to rule-breaking guilt: the Macbeth effect in the sensorimotor regions.

Guilt, a self-conscious emotion, includes self-focused role taking and also correlates with other-oriented role-taking. Excess guilt proneness might be relevant to obsessive compulsive disorders. The white matter (WM) neural correlates of the degree of guilt have not yet been determined. We hypothesized that the WM structures involved in feelings of guilt are associated with social and moral cognition (inferior parietal lobule [IPL], prefrontal cortex [PFC], and cingulate), and aimed to visualize this using diffusion MRI. We investigated the association between regional WM structures (WM volume, and fractional anisotropy, and mean diffusivity [MD]), and feelings of guilt in 1196 healthy, young students using MRI and the Guilty Feeling Scale, which comprises interpersonal situation (IPS; guilt from hurting friends) and rule-breaking situation (RBS; deontological guilt) scores. The primary novel finding presented here is that MD in the right somatosensory and motor cortices from arm to hand were positively correlated with RBS scores. Further, consistent with our hypothesis, RBS scores were positively correlated with MD in the same regions. These results would be predicted by the Macbeth effect, an obsession with dirt leading to hand-washing rituals resulting from guilt, made famous by the Shakespearian character Lady Macbeth. "What, will these hands ne'er be clean?" William Shakespeare (Shakespeare, 1606) Macbeth.

Mean diffusivity related to collectivism among university students in Japan.

Collectivism is an important factor for coping with stress in one's social life. To date, no imaging studies have revealed a direct association between collectivism and white matter structure. Collectivism is positively related to independence, harm avoidance, rejection sensitivity, cooperativeness, external locus of control, and self-monitoring and negatively related to need for uniqueness. Accordingly, we hypothesised that the neural structures underpinning collectivism are those that are also involved with its relationship using magnetic resonance imaging (MRI). This study aimed to identify the brain structures associated with collectivism in healthy young adults (n = 797), using regional grey and white matter volume, fractional anisotropy, and mean diffusivity (MD) analyses of MRI data. Scores on the collectivism scale were positively associated with MD values in the bilateral dorsolateral prefrontal cortex, left orbitofrontal cortex, inferior frontal gyrus, right superior temporal gyrus, ventral posterior cingulate cortex, globus pallidus, and calcarine cortex using the threshold-free cluster enhancement method with family-wise errors corrected to P < 0.05 at the whole-brain level. No significant associations between were found collectivism and other measures. Thus, the present findings supported our hypothesis that the neural correlates of collectivism are situated in regions involved in its related factors.

Effects of Time-Compressed Speech Training on Multiple Functional and Structural Neural Mechanisms Involving the Left Superior Temporal Gyrus.

Time-compressed speech is an artificial form of rapidly presented speech. Training with time-compressed speech (TCSSL) in a second language leads to adaptation toward TCSSL. Here, we newly investigated the effects of 4 weeks of training with TCSSL on diverse cognitive functions and neural systems using the fractional amplitude of spontaneous low-frequency fluctuations (fALFF), resting-state functional connectivity (RSFC) with the left superior temporal gyrus (STG), fractional anisotropy (FA), and regional gray matter volume (rGMV) of young adults by magnetic resonance imaging. There were no significant differences in change of performance of measures of cognitive functions or second language skills after training with TCSSL compared with that of the active control group. However, compared with the active control group, training with TCSSL was associated with increased fALFF, RSFC, and FA and decreased rGMV involving areas in the left STG. These results lacked evidence of a far transfer effect of time-compressed speech training on a wide range of cognitive functions and second language skills in young adults. However, these results demonstrated effects of time-compressed speech training on gray and white matter structures as well as on resting-state intrinsic activity and connectivity involving the left STG, which plays a key role in listening comprehension.

Lenticular nucleus correlates of general self-efficacy in young adults.

General self-efficacy (GSE) is an important factor in education, social participation, and medical treatment. However, the only study that has investigated the direct association between GSE and a neural correlate did not identify specific brain regions, rather only assessed brain structures, and included older adult subjects. GSE is related to motivation, physical activity, learning, the willingness to initiate behaviour and expend effort, and adjustment. Thus, it was hypothesized in the present study that the neural correlates of GSE might be related to changes in the basal ganglia, which is a region related to the abovementioned self-efficacy factors. This study aimed to identify the brain structures associated with GSE in healthy young adults (n = 1204, 691 males and 513 females, age 20.7 ± 1.8 years) using regional grey matter density and volume (rGMD and rGMV), fractional anisotropy (FA) and mean diffusivity (MD) analyses of magnetic resonance imaging (MRI) data. The findings showed that scores on the GSE Scale (GSES) were associated with a lower MD value in regions from the right putamen to the globus pallidum; however, there were no significant association between GSES scores and regional brain structures using the other analyses (rGMD, rGMV, and FA). Thus, the present findings indicated that the lenticular nucleus is a neural correlate of GSE.

Basal ganglia correlates of fatigue in young adults.

Although the prevalence of chronic fatigue is approximately 20% in healthy individuals, there are no studies of brain structure that elucidate the neural correlates of fatigue outside of clinical subjects. We hypothesized that fatigue without evidence of disease might be related to changes in the basal ganglia and prefrontal cortex and be implicated in fatigue with disease. We aimed to identify the white matter structures of fatigue in young subjects without disease using magnetic resonance imaging (MRI). Healthy young adults (n = 883; 489 males and 394 females) were recruited. As expected, the degrees of fatigue and motivation were associated with larger mean diffusivity (MD) in the right putamen, pallidus and caudate. Furthermore, the degree of physical activity was associated with a larger MD only in the right putamen. Accordingly, motivation was the best candidate for widespread basal ganglia, whereas physical activity might be the best candidate for the putamen. A plausible mechanism of fatigue may involve abnormal function of the motor system, as well as areas of the dopaminergic system in the basal ganglia that are associated with motivation and reward.