Memory trace stabilization leads to large-scale changes in the retrieval network: a functional MRI study on associative memory

Spaced learning with time to consolidate leads to more stabile memory traces. However, little is known about the neural correlates of trace stabilization, especially in humans. The present fMRI study contrasted retrieval activity of two well-learned sets of face-location associations, one learned in a massed style and tested on the day of learning (i.e., labile condition) and another learned in a spaced scheme over the course of one week (i.e., stabilized condition). Both sets of associations were retrieved equally well, but the retrieval of stabilized association was faster and accompanied by large-scale changes in the network supporting retrieval. Cued recall of stabilized as compared with labile associations was accompanied by increased activity in the precuneus, the ventromedial prefrontal cortex, the bilateral temporal pole, and left temporo–parietal junction. Conversely, memory representational areas such as the fusiform gyrus for faces and the posterior parietal cortex for locations did not change their activity with stabilization. The changes in activation in the precuneus, which also showed increased connectivity with the fusiform area, are likely to be related to the spatial nature of our task. The activation increase in the ventromedial prefrontal cortex, on the other hand, might reflect a general function in stabilized memory retrieval. This area might succeed the hippocampus in linking distributed neocortical representations.     

Cross-situational consistency of affective experiences across cultures

This study examined cross-situational consistency of affective experiences using an experience-sampling method in Japan, India, and the United States. Participants recorded their moods and situations when signaled at random moments for 7 days. The authors examined relative (interindividual) consistency and absolute (within-person) consistency. They found stable interindividual differences of affective experiences across various situations (mean r =.52 for positive affect.51 for negative affect) and cultural invariance of the cross-situational consistency of affective experiences. Simultaneously, the authors found a considerable degree of within-person cross-situational variation in affective experiences, and cultural differences in within-person cross-situational consistency. Thus, global affective traits exist among non-Western samples, but the degree to which situations exert an influence on the absolute level of affective experience varies across cultures.     

Personality and life satisfaction: a facet-level analysis

At the global level of the Big Five, Extraversion and Neuroticism are the strongest predictors of life satisfaction. However, Extraversion and Neuroticism are multifaceted constructs that combine more specific traits. This article examined the contribution of facets of Extraversion and Neuroticism to life satisfaction in four studies. The depression facet of Neuroticism and the positive emotions/cheerfulness facet of Extraversion were the strongest and most consistent predictors of life satisfaction. These two facets often accounted for more variance in life satisfaction than Neuroticism and Extraversion. The findings suggest that measures of depression and positive emotions/cheerfulness are necessary and sufficient to predict life satisfaction from personality traits. The results also lead to a more refined understanding of the specific personality traits that influence life satisfaction: Depression is more important than anxiety or anger and a cheerful temperament is more important than being active or sociable.     

Culture and well-being: the cycle of action, evaluation, and decision

Two studies were conducted to examine how European and Asian Americans experience and remember their task performance, make a decision about a future task, and how that decision affects enjoyment of the task. In Study 1, although Asians solved as many anagrams as European Americans, Asians remembered solving fewer than did European Americans at Time 2. European Americans' Time 2 choice of task was predicted from Time 1 performance, but Asians' Time 2 choice was not. In Study 2, European Americans chose the same task if they had previously done well and a different task if they had not. Their actual enjoyment of the Time 2 task, furthermore, was significantly higher than at Time 1. In contrast, there was no change in actual enjoyment of the task at Time 2 among Asians because their choice was not based on their performance at Time 1.     

Hemodynamic and electrophysiological connectivity in the language system: Simultaneous near-infrared spectroscopy and electrocorticography recordings during cortical stimulation

We applied near-infrared spectroscopy (NIRS) and electrocorticography (ECoG) recordings during cortical stimulation to a temporal lobe epilepsy patient who underwent subdural electrode implantation. Using NIRS, changes in blood concentrations of oxyhemoglobin (HbO(2)) and deoxyhemoglobin (HbR) during cortical stimulation of the left language areas were measured in each hemisphere. NIRS revealed that 2Hz stimulation with 5mA produced no significant hemodynamic changes in either hemisphere. By contrast, 50Hz stimulation elicited significant increases in both HbO(2) and HbR at the stimulation site. Furthermore, with 50Hz stimulation of the left superior temporal gyrus, the increases in HbO(2) and HbR were observed not only at the stimulation site but also concurrently at the left inferior frontal gyrus. This suggests the existence of functional connectivity in the language system. The present study demonstrates that simultaneous NIRS and ECoG studies during cortical stimulation allow a novel analysis of cerebral connectivity.     

Serum levels of brain-derived neurotrophic factor (BDNF), BDNF gene Val66Met polymorphism, or plasma catecholamine metabolites, and response to mirtazapine in Japanese patients with major depressive disorder (MDD)

Object We investigated an association between the polymorphism of brain-derived neurotrophic factor (BDNF) gene Val66Met and the response to mirtazapine in Japanese patients with major depressive disorder (MDD). We also examined mirtazapine's effects on the serum BDNF and plasma levels of catecholamine metabolites in these patients. METHODS: Eighty-four patients who met the DSM-IV-TR criteria for MDD were treated with only mirtazapine for 4 weeks. The BDNF Val66Met polymorphism was detected by direct sequencing in the region, and serum BDNF levels and plasma levels of catecholamine metabolites were measured by ELISA and HPLC-ECD, respectively. RESULTS: Mirtazapine treatment for 4 weeks significantly increased serum BDNF levels in the responders, whereas nonresponders showed significant decreases. No association was found between either of the two genotypes (Val/Val vs. Met-carriers) and the response to mirtazapine at T4 or the serum BDNF levels at T0. Mirtazapine did not alter the plasma levels of homovanillic acid (HVA) or 3-methoxy-4-hydroxyphenylglycol (MHPG). Discussion The dynamics of serum BDNF levels, but not plasma levels of HVA and MHPG, reflect the response to mirtazapine treatment; the BDNF Val66Met polymorphism in patients with depression is, however, associated with neither a particular response to mirtazapine treatment nor baseline serum BDNF levels. Conclusion Serum BDNF levels, but not plasma levels of HVA or MHPG, and BDNF Val66Met polymorphism are related to the mirtazapine response in MDD.     

Do postpartum anxiety and breastfeeding self-efficacy and bonding at early postpartum predict postpartum depression and the breastfeeding method?

We investigated whether postpartum anxiety (PPA) and breastfeeding self-efficacy and bonding at the early postpartum period can be used to predict postpartum depression and the breastfeeding method, and we sought to identify factors related to postpartum depression. Of the 510 eligible women, 185 (36%) returned the questionnaire on all three occasions (1 day, 3 days, and 1 month after childbirth). The mothers' progress on the State-Trait Anxiety Inventory (STAI), Breastfeeding Self-Efficacy Scale Short Form (BFSES-SF), and Postnatal Bonding Questionnaire (PBQ) was observed over three periods. A repeated-measures ANOVA revealed that the mothers at high risk of developing postpartum depression (PPD) were those who did not show an increase in BFSES-SF score at early postpartum, and mothers whose bonding disorders have deteriorated rapidly. The results of the logistic regression analysis revealed a significant difference in employment as a factor related to postpartum depression. Compared to Regular, Part-time status was 4.4 times more likely and Unemployed status was 2.3 times more likely to cause postpartum depression. For the early detection of PPD, it is necessary to identify (1) mothers who do not show an increase in the BFSES-SF score, (2) mothers whose bonding disorders have deteriorated rapidly, and (3) part-time or unemployed mothers as characteristic of postpartum depression.     

Cultural influences on the relation between pleasant emotions and unpleasant emotions: Asian dialectic philosophies or individualism-collectivism?

The present study examined the hypothesis that Asian cultures' dialectical way of thinking influences emotion reports. A dialectical way of thinking sees emotions of the opposite valence (e.g., happy, sad) as compatible with each other. In contrast, Western philosophy considers these emotions to be in conflict with each other. We examined correlations between frequency estimates of pleasant emotions (FPE) and frequency estimates of unpleasant emotions (FUE) in Asian, non-Asian collectivistic, and Western cultures. As predicted, FPE-FUE correlations were less negative in Asian cultures than in other cultures. We also observed a tendency for the culture effect to be moderated by gender. The strongest negative correlation was obtained for women in non-Asian cultures.