Trace-element and isotopic characteristics of small-degree melts of the asthenosphere: Evidence from the alkalic basalts of the Antarctic Peninsula

Miocene-Recent continental alkalic basalts were erupted along the Antarctic Peninsula as a result of decompressional melting of the asthenosphere caused by the formation of slab-windows beneath the continental margin following the cessation of subduction. The basalts appear not to be related to a period of major lithospheric attenuation, nor were they formed as a result of the influence of a mantle plume. They exhibit strong trace-element and isotopic affinities with OIB, Sr- and Nd-isotope compositions ranging from 0.70269 to 0.70343 and 0.512863 to 0.51300, respectively, similar to the composition of HIMU OIB. However, new Pb-isotope analyses show that 206Pb204Pb ratios (18.79–19.28) fall within the range for E-type MORB with Δ84 and Δ74 varying from −28 to +26 and from +1 to +10, respectively. Δ84-values , Sr-isotope ratios and some LILE/HFSE ratios exhibit negative covariations with LanYbn and Nb/Y ratios implying some control of degree of partial melting on geochemical composition. Nb/U ratios (14–40) are considerably lower than most OIB and MORB. The basalts also have unusually low absolute abundances of Rb and Ba and high K/Ba and K/Rb ratios (50–140 and 400–1500, respectively). Correlated PbSrNd isotope and trace-element behaviour suggests that the asthenosphere from which these basalts were derived was subjected to multiple melt extraction/depletion events. One period of melt extraction was ancient (∼ 1.7 Ga) and similar to that affecting MORB source mantle, and was followed by a more recent (?Mesozoic) event. This more recent event resulted in increased U/Pb, U/Nb and U/Th ratios and further depletion in ultra-incompatible element such as Rb and Ba, causing high K/Rb and K/Ba ratios in the erupted lavas. This implies that the asthenosphere beneath the Antarctic Peninsula is heterogeneous on a small scale. Small-degree melts are capable of sampling geochemically, and possibly mineralogically, distinct mantle domains from larger-degree melts. During larger degrees of partial melting, the scale of melting approaches the scale of heterogeneity and integration of melts from different geochemical domains occurs

A structural MRI study of motor conversion disorder: evidence of reduction in thalamic volume.

OBJECTIVE: To investigate potential abnormalities in subcortical brain structures in conversion disorder (CD) compared with controls using a region of interest (ROI) approach. METHODS: Fourteen patients with motor CD were compared with 31 healthy controls using high-resolution MRI scans with an ROI approach focusing on the basal ganglia, thalamus and amygdala. Brain volumes were measured using Freesurfer, a validated segmentation algorithm. RESULTS: Significantly smaller left thalamic volumes were found in patients compared with controls when corrected for intracranial volume. These reductions did not vary with handedness, laterality, duration or severity of symptoms. CONCLUSIONS: These differences may reflect a primary disease process in this area or be secondary effects of the disorder, for example, resulting from limb disuse. Larger, longitudinal structural imaging studies will be required to confirm the findings and explore whether they are primary or secondary to CD

Neural activation during cognitive reappraisal in girls at high risk for depression

WOS: 000404308100006PubMed ID: 28372994Objective: Although emotion dysregulation, one of the core features of depression, has long been thought to be a vulnerability factor for major depressive disorder (MDD), surprisingly few functional magnetic resonance imaging (fMRI) studies have investigated neural correlates of emotion regulation strategies in unaffected high risk individuals. Method: Sixteen high risk (RSK) young women and fifteen matched low risk controls (CU) were scanned using fMRI while performing an emotion regulation task. During this task, participants were instructed to reappraise their negative emotions elicited by International Affective Picture System images (TAPS). In addition, Difficulties in Emotion Regulation Strategies Scale (DERS) was used to assess participants' emotion dysregulation levels. Results: Both RSK and CTL individuals show increased amygdala activation in response to negative emotional stimuli, however no difference was found between groups in using cognitive reappraisal strategies and functions of brain regions implicated in cognitive reappraisal. Interestingly, our psychometric test results indicate that high risk individuals are characterised by lower perceived emotional clarity (EC). Conclusion: Results of the current study suggest depression vulnerability may not be linked to the effectiveness of cognitive reappraisal. Alternatively, lower EC may be a vulnerability factor for depression.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [1001, 109S134]; UK Medical Research Council FellowshipMedical Research Council UK (MRC) [MR/J008915/1]This research was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) grant 1001 with the project number 109S134 to Ali Saffet Gonul. Matthew J. Kempton was funded by a UK Medical Research Council Fellowship (grant MR/J008915/1)

Psychological processes underlying the association between childhood trauma and psychosis in daily life:an experience sampling study

BACKGROUND: Evidence has accumulated that implicates childhood trauma in the aetiology of psychosis, but our understanding of the putative psychological processes and mechanisms through which childhood trauma impacts on individuals and contributes to the development of psychosis remains limited. We aimed to investigate whether stress sensitivity and threat anticipation underlie the association between childhood abuse and psychosis. METHOD: We used the Experience Sampling Method to measure stress, threat anticipation, negative affect, and psychotic experiences in 50 first-episode psychosis (FEP) patients, 44 At-Risk Mental State (ARMS) participants, and 52 controls. Childhood abuse was assessed using the Childhood Trauma Questionnaire. RESULTS: Associations of minor socio-environmental stress in daily life with negative affect and psychotic experiences were modified by sexual abuse and group (all p FWE < 0.05). While there was strong evidence that these associations were greater in FEP exposed to high levels of sexual abuse, and some evidence of greater associations in ARMS exposed to high levels of sexual abuse, controls exposed to high levels of sexual abuse were more resilient and reported less intense negative emotional reactions to socio-environmental stress. A similar pattern was evident for threat anticipation. CONCLUSIONS: Elevated sensitivity and lack of resilience to socio-environmental stress and enhanced threat anticipation in daily life may be important psychological processes underlying the association between childhood sexual abuse and psychosis

Late-life obesity is associated with smaller global and regional gray matter volumes: a voxel-based morphometric study

OBJECTIVE: Obesity adversely affects frontal lobe brain structure and function. Here we sought to show that people who are obese versus those who are of normal weight over a 5-year period have differential global and regional brain volumes. DESIGN: Using voxel-based morphometry, contrasts were done between those who were recorded as being either obese or of normal weight over two time points in the 5 years prior to the brain scan. In a post-hoc preliminary analysis, we compared scores for obese and normal weight people who completed the trail-making task. SUBJECTS: A total of 292 subjects were examined following exclusions (for example, owing to dementia, stroke and cortical infarcts) from the Prospective Investigation of the Vasculature in Uppsala Seniors cohort with a body mass index of normal weight (<25 kg m(−2)) or obese (⩾30 kg m(−2)). RESULTS: People who were obese had significantly smaller total brain volumes and specifically, significantly reduced total gray matter (GM) volume (GMV) (with no difference in white matter or cerebrospinal fluid). Initial exploratory whole brain uncorrected analysis revealed that people who were obese had significantly smaller GMV in the bilateral supplementary motor area, bilateral dorsolateral prefrontal cortex (DLPFC), left inferior frontal gyrus and left postcentral gyrus. Secondary more stringent corrected analyses revealed a surviving cluster of GMV difference in the left DLPFC. Finally, post-hoc contrasts of scores on the trail-making task, which is linked to DLPFC function, revealed that obese people were significantly slower than those of normal weight. CONCLUSION: These findings suggest that in comparison with normal weight, people who are obese have smaller GMV, particularly in the left DLPFC. Our results may provide evidence for a potential working memory mechanism for the cognitive suppression of appetite that may lower the risk of developing obesity in later life