Current Issue : January - March Volume : 2013 Issue Number : 1 Articles : 5 Articles
Background: During normal semantic processing, the left hemisphere (LH) is suggested to restrict right\r\nhemisphere (RH) performance via interhemispheric suppression. However, a lesion in the LH or the use of\r\nconcurrent tasks to overload the LH�s attentional resource balance has been reported to result in RH disinhibition\r\nwith subsequent improvements in RH performance. The current study examines variations in RH semantic\r\nprocessing in the context of unilateral LH lesions and the manipulation of the interhemispheric processing\r\nresource balance, in order to explore the relevance of RH disinhibition to hemispheric contributions to semantic\r\nprocessing following a unilateral LH lesion.\r\nMethods: RH disinhibition was examined for nine participants with a single LH lesion and 13 matched controls\r\nusing the dual task paradigm. Hemispheric performance on a divided visual field lexical decision semantic priming\r\ntask was compared over three verbal memory load conditions, of zero-, two- and six-words. Related stimuli\r\nconsisted of categorically related, associatively related, and categorically and associatively related prime-target pairs.\r\nResponse time and accuracy data were recorded and analyzed using linear mixed model analysis, and planned\r\ncontrasts were performed to compare priming effects in both visual fields, for each of the memory load conditions.\r\nResults: Control participants exhibited significant bilateral visual field priming for all related conditions (p < .05),\r\nand a LH advantage over all three memory load conditions. Participants with LH lesions exhibited an improvement\r\nin RH priming performance as memory load increased, with priming for the categorically related condition\r\noccurring only in the 2- and 6-word memory conditions. RH disinhibition was also reflected for the LH damage\r\n(LHD) group by the removal of the LH performance advantage following the introduction of the memory load\r\nconditions.\r\nConclusions: The results from the control group are consistent with suggestions of an age related hemispheric\r\nasymmetry reduction and indicate that in healthy aging compensatory bilateral activation may reduce the impact\r\nof inhibition. In comparison, the results for the LHD group indicate that following a LH lesion RH semantic\r\nprocessing can be manipulated and enhanced by the introduction of a verbal memory task designed to engage\r\nLH resources and allow disinhibition of RH processing....
Background: Apathy is frequently observed in numerous neurological disorders, including Alzheimer�s and\r\nParkinson�s, as well as neuropsychiatric disorders including schizophrenia. Apathy is defined as a lack of motivation\r\ncharacterized by diminished goal-oriented behavior and self-initiated activity. This study evaluated a chronic\r\nrestraint stress (CRS) protocol in modeling apathetic behavior, and determined whether administration of an\r\nanticholinesterase had utility in attenuating CRS-induced phenotypes.\r\nMethods: We assessed behavior as well as regional neuronal activity patterns using FosB immunohistochemistry\r\nafter exposure to CRS for 6 h/d for a minimum of 21 d. Based on our FosB findings and recent clinical trials, we\r\nadministered an anticholinesterase to evaluate attenuation of CRS-induced phenotypes.\r\nResults: CRS resulted in behaviors that reflect motivational loss and diminished emotional responsiveness. CRSexposed\r\nmice showed differences in FosB accumulation, including changes in the cholinergic basal forebrain\r\nsystem. Facilitating cholinergic signaling ameliorated CRS-induced deficits in initiation and motivational drive and\r\nrescued immediate early gene activation in the medial septum and nucleus accumbens.\r\nConclusions: Some CRS protocols may be useful for studying deficits in motivation and apathetic behavior.\r\nAmelioration of CRS-induced behaviors with an anticholinesterase supports a role for the cholinergic system in\r\nremediation of deficits in motivational drive...
Background: Several studies have hypothesized that genes regulating the components of the serotonin system,\r\nincluding serotonin transporter (5-HTTLPR) and serotonin 1 B receptor (5-HT1B), may be associated with alcoholism,\r\nbut their results are contradictory because of alcoholism�s heterogeneity. Therefore, we examined whether the 5-\r\nHTTLPR gene and 5-HT1B gene G861C polymorphism are susceptibility factors for a specific subtype of alcoholism,\r\nantisocial alcoholism in Han Chinese in Taiwan.\r\nMethods: We recruited 273 Han Chinese male inmates with antisocial personality disorder (ASPD) [antisocial\r\nalcoholism (AS-ALC) group (n = 120) and antisocial non-alcoholism (AS-N-ALC) group (n = 153)] and 191 healthy\r\nmale controls from the community. Genotyping was done using PCR-RFLP.\r\nResults: There were no significant differences in the genotypic frequency of the 5-HT1B G861C polymorphism\r\nbetween the 3 groups. Although AS-ALC group members more frequently carried the 5-HTTLPR S/S, S/LG, and LG/LG\r\ngenotypes than controls, the difference became non-significant after controlling for the covarying effects of age.\r\nHowever, the 5-HTTLPR S/S, S/LG, and LG/LG genotypes may have interacted with the 5-HT1B G861C C/C\r\npolymorphism and increased the risk of becoming antisocial alcoholism.\r\nConclusion: Our study suggests that neither the 5-HTTLPR gene nor the 5-HT1B G861C polymorphism alone is a risk\r\nfactor for antisocial alcoholism in Taiwan�s Han Chinese population, but that the interaction between both genes\r\nmay increase susceptibility to antisocial alcoholism....
Depression in bipolar disorder has long been thought to be a state characterized by mental inactivity. However,\r\nrecent research demonstrates that patients with bipolar disorder engage in rumination, a form of self-focused\r\nrepetitive cognitive activity, in depressed as well as in manic states. While rumination has long been associated\r\nwith depressed states in major depressive disorder, the finding that patients with bipolar disorder ruminate in\r\nmanic states is unique to bipolar disorder and challenges explanations put forward for why people ruminate. We\r\nreview the research on rumination in bipolar disorder and propose that rumination in bipolar disorder, in both\r\nmanic and depressed states, reflects executive dysfunction. We also review the neurobiology of bipolar disorder\r\nand recent neuroimaging studies of rumination, which is consistent with our hypothesis that the tendency to\r\nruminate reflects executive dysfunction in bipolar disorder. Finally, we relate the neurobiology of rumination to the\r\nneurobiology of emotion regulation, which is disrupted in bipolar disorder....
Background: RGS17 and RGS20 encode two members of the regulator of G-protein signaling RGS-Rz subfamily.\r\nVariation in these genes may alter their transcription and thereby influence the function of G protein-coupled\r\nreceptors, including opioid receptors, and modify risk for substance dependence.\r\nMethods: The association of 13 RGS17 and eight RGS20 tag single nucleotide polymorphisms (SNPs) was examined\r\nwith four substance dependence diagnoses (alcohol (AD), cocaine (CD), opioid (OD) or marijuana (MjD)] in 1,905\r\nAfrican Americans (AAs: 1,562 cases and 343 controls) and 1,332 European Americans (EAs: 981 cases and 351\r\ncontrols). Analyses were performed using both ?2 tests and logistic regression analyses that covaried sex, age, and\r\nancestry proportion. Correlation of genotypes and mRNA expression levels was assessed by linear regression\r\nanalyses.\r\nResults: Seven RGS17 SNPs showed a significant association with at least one of the four dependence traits after a\r\npermutation-based correction for multiple testing (0.003=Pempirical=0.037). The G allele of SNP rs596359, in the\r\nRGS17 promoter region, was associated with AD, CD, OD, or MjD in both populations (0.005=Pempirical=0.019).\r\nThis allele was also associated with significantly lower mRNA expression levels of RGS17 in YRI subjects\r\n(P = 0.002) and non-significantly lower mRNA expression levels of RGS17 in CEU subjects (P = 0.185). No RGS20\r\nSNPs were associated with any of the four dependence traits in either population.\r\nConclusions: This study demonstrated that variation in RGS17 was associated with risk for substance\r\ndependence diagnoses in both AA and EA populations....
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