739 research outputs found

    P S Y C H O L O G Y

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    A l t e r e d f r o n t a l c o r t i c a l v o l u m e a n d d e c i s i o n m a k i n g in a d o l e s c e n t c a n n a b i s u s e r s Anticipating future outcom es is central to decision making and a failure to consider long-term co n sequences may lead to impulsive choices. A dolescence is a vulnerable period during which underdeveloped prefrontal cortical system s may contribute to poor judgment, impulsive choices, and substance abuse. Conversely, substance abuse during this period may alter neural system s involved in decision making and lead to greater impulsivity. Although a broad neural network which supports decision making undergoes extensive change during adolescent development, one region that may be critical is the medial prefrontal cortex. Altered functional integrity of this region may be specifically related to reward perception, substance abuse, and dependence. In the present investigation, w e acquired structural m agnetic resonance im ages (MRI), using a 3T SiemensTrio scanner, from 18 cannabis abusing adolescents (CA; 2 female and 16 male subjects; m ean age, 17.7 years; range 16-19 years), and 18 healthy controls (HC; 6 female and 12 male subjects; m ean age, 17.2 years; range 16-19 years). In order to m easure medial orbital prefrontal cortex (moPFC) morphology related to su b stan c e ab u se and impulsivity, sem i autom ated cortical reconstruction and volumetric segm entation of MRIs w as performed with FreeSurfer. Impulsivity w as evaluated with the Barratt Impulsiveness Scale (BIS). J o h n C. C h u r c h w e ll1, M e lis s a L o p e z -L a r s o n 12 a n d D e b o r a h A . Y u r g e lu n -T o d d 1

    Local brain connectivity and associations with gender and age

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    ABSTRACTRegional homogeneity measures synchrony of resting-state brain activity in neighboring voxels, or local connectivity. The effects of age and gender on local connectivity in healthy subjects are unknown. We performed regional homogeneity analyses on resting state BOLD time series data acquired from 58 normal, healthy participants, ranging in age from 11 to 35 (mean 18.1±5.0 years, 32 males). Regional homogeneity was found to be highest for gray matter, with brain regions within the default mode network having the highest local connectivity values. There was a general decrease in regional homogeneity with age with the greatest reduction seen in the anterior cingulate and temporal lobe. Greater female local connectivity in the right hippocampus and amygdala was also noted, regardless of age. These findings suggest that local connectivity at the millimeter scale decreases during development as longer connections are formed, and underscores the importance of examining gender differences in imaging studies of healthy and clinical populations

    Permutation testing made practical for functional magnetic resonance image analysis

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    We describe an efficient algorithm for the step-down permutation test, applied to the analysis of functional magnetic resonance images. The algorithm's time bound is nearly linear, making it feasible as an interactive tool. Results of the permutation test algorithm applied to data from a cognitive activation paradigm are compared with those of a standard parametric test corrected for multiple comparisons. The permutation test identifies more weakly activated voxels than the parametric test, always activates a superset of the voxels activated by this parametric method, almost always yields significance levels greater than or equal to those produced by the parametric method, and tends to enlarge activated clusters rather than adding isolated voxels. Our implementation of the permutation test is freely available as part of a widely distributed software package for analysis of functional brain images

    Functional connectivity during a social emotion task in adolescents and in adults

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    In this fMRI study we investigated functional connectivity between components of the mentalising system during a social emotion task, using psychophysiological interaction (PPI) analysis. Ten adults (22–32 years) and 18 adolescents (11–18 years) were scanned while thinking about scenarios in which a social or a basic emotion would be experienced. Unlike basic emotions (such as disgust and fear), social emotions (such as embarrassment and guilt) require the representation of another's mental states. In both adults and adolescents, an anterior rostral region of medial prefrontal cortex (arMPFC) involved in mentalising showed greater connectivity with the posterior superior temporal sulcus (pSTS) bordering on the temporo-parietal junction (TPJ) and with anterior temporal cortex (ATC) during social than during basic emotion. This result provides novel evidence that components of the mentalising system interact functionally during a social emotion task. Furthermore, functional connectivity differed between adolescence and adulthood. The adolescent group showed stronger connectivity between arMPFC and pSTS/TPJ during social relative to basic emotion than did the adult group, suggestive of developmental changes in functional integration within the mentalising system

    Lynch Syndrome - Cancer Pathways, Heterogeneity and Immune Escape

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    Recent work has provided evidence for genetic and molecular heterogeneity in colorectal cancers (CRCs) arising in patients with Lynch syndrome (LS), dividing these into two groups: G1 and G2. In terms of mutation and gene expression profile, G1 CRCs bear resemblance to sporadic CRCs with microsatellite instability (MSI), whereas G2 CRCs are more similar to microsatellite stable CRCs. Here we review the current state of knowledge on pathways of precursor progression to CRC in LS and how these might tie in with the new findings. Immunotherapies are an active field of research for MSI cancers and their potential use for cancer therapy for both sporadic and LS MSI cancers is discussed
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