References of "Cortex : A Journal Devoted to the Study of the Nervous System & Behavior"
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See detailEffects of transcranial direct current stimulation (tDCS) on executive functions: influence of COMT Val/Met polymorphism.
Plewnia, Christian; Zwissler, Bastian; Langst, Isabella et al

in Cortex : A Journal Devoted to the Study of the Nervous System & Behavior (2013), 49(7), 1801-7

INTRODUCTION: Transcranial direct current stimulation (tDCS) is a frequently used technique to investigate healthy and impaired neuronal functions. Its modulatory effect on executive functions is of ... [more ▼]

INTRODUCTION: Transcranial direct current stimulation (tDCS) is a frequently used technique to investigate healthy and impaired neuronal functions. Its modulatory effect on executive functions is of particular interest for understanding the mechanisms underlying integration of cognition and behavior. The key role of prefrontal dopamine function for executive functions suggest that differences of the Val158Met polymorphism of the catechol-O-methyltransferase (COMT) gene would interact with tDCS interventions in this domain. In this study, we hypothesized that the COMT Met allele homozygosity, associated with higher levels of prefrontal dopamine, would influence the effect of tDCS on higher-level executive functions. METHOD: Forty-six healthy subjects participated in a double-blind sham-controlled crossover study and underwent COMT genotyping. Anodal tDCS (20 min, 1 mA) to the left dorsolateral prefrontal cortex (dlPFC) or sham stimulation was applied during the performance of a parametric Go/No-Go (PGNG) test measuring sustained attention, response inhibition and cognitive flexibility as measured by set-shifting. RESULTS: In COMT Met/Met allele carrier anodal tDCS of the dlPFC was associated with a deterioration of set-shifting ability, which is assessed by the most challenging level of the PGNG. Without regard to the carrier status of the COMT Val158Met polymorphism no effects of anodal tDCS on executive functions could be determined. CONCLUSIONS: In line with the model of non-linear effects of l-dopa on cortical plasticity high dopaminergic prefrontal activity mediated by COMT Val158Met polymorphism predicts a detrimental effect of anodal tDCS on cognitive flexibility. Therefore, we suggest that the individual genetic profile may modulate behavioral effect of tDCS. More precise application of brain stimulation techniques according to the individual genetic patterns may support the development of personalized treatment approaches. [less ▲]

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See detailA multidimensional approach to impulsivity changes in mild Alzheimer's disease and control participants: cognitive correlates.
Rochat, Lucien; Billieux, Joël UL; Juillerat Van der Linden, Anne-Claude et al

in Cortex : A Journal Devoted to the Study of the Nervous System & Behavior (2013), 49(1), 90-100

INTRODUCTION: Impulsive behaviors are frequently described in brain-damaged patients, including patients with Alzheimer's disease (AD). However, few studies have examined impulsivity changes and ... [more ▼]

INTRODUCTION: Impulsive behaviors are frequently described in brain-damaged patients, including patients with Alzheimer's disease (AD). However, few studies have examined impulsivity changes and associated cognitive impairments in AD and healthy controls. Consequently, the first aim of this study was to compare patients with mild AD and matched controls on four dimensions of impulsivity (urgency, lack of premeditation, lack of perseverance, and sensation seeking) recently highlighted in the literature. The second objective was to examine the association between impulsivity changes and cognitive performances on executive/attentional tasks in mild AD and healthy controls. METHODS: Thirty patients with mild AD and 30 matched controls were administered a battery of tests that assessed executive and attention processes. In addition, informants of each patient and control completed a short questionnaire designed to assess the changes on the four dimensions of impulsivity (Rochat et al., 2008). RESULTS: Patients with mild AD had higher scores than controls on lack of premeditation and lack of perseverance dimensions of impulsivity, whereas the two groups did not differ on urgency and sensation seeking. Furthermore, patients showed significant decreased performances on measures of inhibition of prepotent responses, set-shifting, and working memory, as well as higher variability of reaction times (RTs) than matched controls. Regression analyses computed on the whole sample emphasized that difficulties in inhibition of prepotent responses significantly predicted higher lack of premeditation, and larger variability of RTs and set-shifting difficulties significantly predicted higher lack of perseverance, even when global cognitive functioning, general processing speed, working memory, and age were controlled for. Urgency and sensation seeking were not associated with any variables. CONCLUSIONS: These results provide valuable insight into the nature of brain systems and cognitive processes underlying impulsive behaviors. In addition, they open up interesting prospects for better comprehension of behavioral and psychological symptoms of AD. [less ▲]

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See detailA pet study of human skill learning: Changes in brain activity related to learning an orientation discrimination task
Schiltz, Christine UL; Bodart, Jean-Michel; Michel, Christian et al

in Cortex : A Journal Devoted to the Study of the Nervous System & Behavior (2001), 37(2), 243-265

Using 15O-water 3D positron emission tomography we investigated the effect of training in orientation discrimination upon cerebral activity in healthy human adults. When subjects are trained in this ... [more ▼]

Using 15O-water 3D positron emission tomography we investigated the effect of training in orientation discrimination upon cerebral activity in healthy human adults. When subjects are trained in this discrimination task, they learn the visuo-motor stimulus-response association required by the task and they increase their perceptual abilities in orientation discrimination. The present study was designed to investigate the rCBF modifications related to both these learning processes induced by training in orientation discrimination. PET data were acquired on two separate days (before and after training). Comparing the activation pattern related to orientation discrimination before and after the training period we observed activity decreases located in the left cerebellar cortex, in the right precentral gyrus and bilaterally in the fusiform gyri. The only region showing an activity increase was located in the body of the right caudate nucleus. These findings confirm the role of the neostriatum in skill learning and highlight the importance of mechanisms resulting in cortical and cerebellar neuronal activity decreases in this type of learning. [less ▲]

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