Brain Perfusion Alterations Induced by Standalone and Combined Non-Invasive Brain Stimulation over the Dorsolateral Prefrontal Cortex.

Non-invasive brain stimulation (NIBS) interventions are promising for the treatment of psychiatric disorders. Notwithstanding, the NIBS mechanisms of action over the dorsolateral prefrontal cortex (DLPFC), a hub that modulates affective and cognitive processes, have not been completely mapped. We aimed to investigate regional cerebral blood flow (rCBF) changes over the DLPFC and the subgenual anterior cingulate cortex (sgACC) of different NIBS protocols using Single-Photon Emission Computed Tomography (SPECT). A factorial, within-subjects, double-blinded study was performed. Twenty-three healthy subjects randomly underwent four sessions of NIBS applied once a week: transcranial direct current stimulation (tDCS), intermittent theta-burst stimulation (iTBS), combined tDCS + iTBS and placebo. The radiotracer 99m-Technetium-ethylene-cysteine-dimer was injected intravenously during the NIBS session, and SPECT neuroimages were acquired after the session. Results revealed that the combination of tDCS + iTBS increased right sgACC rCBF. Cathodal and anodal tDCS increased and decreased DLPFC rCBF, respectively, while iTBS showed no significant changes compared to the placebo. Our findings suggest that the combined protocol might optimize the activity in the right sgACC and encourage future trials with neuropsychiatric populations. Moreover, mechanistic studies to investigate the effects of tDCS and iTBS over the DLPFC are required.

Psychiatric profile and quality of life of subjects with excess weight treated with transcranial direct current stimulation combined with a hypocaloric diet.

Background: Transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC) may reduce appetite and caloric intake and may be able to play a role as an adjunct treatment for obesity. Stimulation of this brain area is also used for the treatment of depression, which shares a common pathophysiology with obesity. As a result, the effect of tDCS on mental health and its impact on the quality of life of subjects with excess weight needs to be addressed.Objective: To assess the effect of daily tDCS of the right DLPFC on mood, daytime sleepiness, anxiety and quality of life in subjects with excess weight on a hypocaloric diet.Methods: We randomly assigned 28 subjects to receive 20 sessions of active or sham tDCS over the right DLPFC for 20 consecutive weekdays. The severity of depressive and anxiety symptoms was assessed by the Beck Depression Inventory (BDI) and the State-Trait Anxiety Inventory-State (STAI-S). Sleepiness was measured by a daytime sleepiness questionnaire (DSQ), and quality of life was measured by the 36-Item Short Form Health Survey (SF-36).Results: There were no significant changes in BDI, STAI-S and DSQ scores between groups, even after adjustments for the use of antidepressant medications and changes in body weight. There were also no significant changes in different subscales of the SF-36 quality of life questionnaire between groups.Conclusion: Repetitive tDCS on the right DLPFC is not associated with impairment in mental health or quality of life in overweight and obese subjects.

Age as a Mediator of tDCS Effects on Pain: An Integrative Systematic Review and Meta-Analysis.

Introduction: The transcranial direct current stimulation (tDCS) is a neuromodulatory technique with the potential to decrease pain scores and to improve chronic pain treatment. Although age is an essential factor that might impact the tDCS effect, most studies are solely conducted in adults. Therefore, the age limitation presents a critical research gap in this field and can be shown by only a handful of studies that have included other age groups. To examine the evidence upon the tDCS effect on pain scores on children, adolescents, or elderly, and indirectly, to infer the age-dependent impact on tDCS effects, we conducted a systematic review and meta-analysis. Methods: A systematic review searching the following databases: PubMed, EMBASE, and Science Direct using the following search terms adapted according to MeSh or Entree: [("Adolescent" OR "Children" OR "Elderly") AND ("tDCS") AND ("Pain" OR "Pain threshold") AND ("dorsolateral prefrontal cortex" OR "Motor cortex)] up to April 20th, 2020. We retrieved 228 articles, 13 were included in the systematic review, and five studies with elderly subjects that had their outcomes assessed by pain score or pain threshold were included in the meta-analysis. Results: For the analysis of pain score, 96 individuals received active stimulation, and we found a favorable effect for active tDCS to reduce pain score compared to sham (P = 0.002). The standardized difference was -0.76 (CI 95% = -1.24 to -0.28). For the pain threshold, the analysis showed no significant difference between active and sham tDCS. We reviewed two studies with adolescents: one study using anodal tDCS over the prefrontal cortex reported a reduction in pain scores. However, the second study reported an increase in pain sensitivity for the dorsolateral prefrontal cortex (DLPFC) stimulation. Conclusion: Our findings suggest tDCS may reduce pain levels in the elderly group. Nevertheless, the small number of studies included in this review-and the considerable heterogeneity for clinical conditions and protocols of stimulation present-limits the support of tDCS use for pain treatment in elderly people. Larger studies on the tDCS effect on pain are needed to be conducted in elderly and adolescents, also evaluating different montages and electrical current intensity.

Efeito da estimulação transcraniana por corrente continua (ETCC) no córtex préfrontal dorsolateral sobre a reprodução de intervalo de tempo / Effect of Transcranial direct current stimulation (tDCS) on dorsolateral prefrontal cortex on reproduction of time

Existem evidências que apontam para a importância do córtex préfrontal dorsolateral (CPFDL) na percepção de intervalos de tempo. A ETCC (eletroestimulação transcraniana por corrente contínua) modula a excitabilidade cortical, podendo ser utilizada para influenciar o desempenho de diferentes funções cerebrais, como a estimativa de tempo. Nosso objetivo foi avaliar o efeito da estimulação do CPFDL direito e esquerdo sobre a reprodução de intervalos de tempo. 26 indivíduos foram submetidos a estimulação transcraniana de 2mA no CPFDL por 20 min (anódica, catódica ou sham). Em seguida, participaram de uma tarefa de reprodução de intervalos de tempo de 4 e 8 segundos. Através de ANOVA para medidas repetidas para os fatores estimulação (anódica, catódica, sham), Intervalos (4s e/ou 8s) e local (esquerdo e direito), pudemos observar que a estimulação anódica do CPFDL do hemisfério direito resultou em subestimativa maior no intervalo de 4 segundos, enquanto o uso de corrente catódica sobre o CPFDL esquerdo provocou uma superestimativa do tempo para o intervalo de 4 segundos. Nossos resultados corroboram a importância do CPFDL direito na percepção de tempo. Ainda, o efeito assimétrico observado é interessante, confirmando que o CPFDL esquerdo está associado às funções executivas, importantes na percepção de tempo.

There is evidence supporting the importance of the dorsolateral prefrontal cortex (DLPFC) in the perception of time. The tDCS (transcranial direct current stimulation) modulates cortical excitability and can be applied to influence the performance of different brain functions, such as timing. Our objective was to evaluate the effect of stimulation of right and left DLPFC on a task of production of time. 26 patients underwent transcranial stimulation of 2mA over the DLPFC for 20 min (anodic, cathodic or sham). Then they participated in a reproduction task of 4 and 8 seconds. Through ANOVA for repeated measures for stimulating factors (anode, cathode, sham), intervals (4S and / or 8s) and location (left and right), we observed that the anodic stimulation of the right DLPFC resulted in greater underestimation in 4-seconds interval, while the use of cathodic current on the left DLPFC caused an overestimation of 4-seconds interval. Our results confirm the importance of the right DLPFC in the perception of time. Furthermore, the observed asymmetric effect is interesting, confirming that the left DLPFC is associated with the executive, important roles in perception of time.

Ascending monoaminergic systems alterations in Alzheimer's disease. translating basic science into clinical care.

Extensive neuropathological studies have established a compelling link between abnormalities in structure and function of subcortical monoaminergic (MA-ergic) systems and the pathophysiology of Alzheimer's disease (AD). The main cell populations of these systems including the locus coeruleus, the raphe nuclei, and the tuberomamillary nucleus undergo significant degeneration in AD, thereby depriving the hippocampal and cortical neurons from their critical modulatory influence. These studies have been complemented by genome wide association studies linking polymorphisms in key genes involved in the MA-ergic systems and particular behavioral abnormalities in AD. Importantly, several recent studies have shown that improvement of the MA-ergic systems can both restore cognitive function and reduce AD-related pathology in animal models of neurodegeneration. This review aims to explore the link between abnormalities in the MA-ergic systems and AD symptomatology as well as the therapeutic strategies targeting these systems. Furthermore, we will examine possible mechanisms behind basic vulnerability of MA-ergic neurons in AD.

Neural activity during Stroop colour-word task performance in late proficient bilinguals: a functional magnetic resonance imaging study

The aim of this study was to identify which neural substrates are engaged during manual Stroop task performance and compare the activation between 8 late proficient Macedonian-English bilinguals and 10 matched English monolinguals. During functional magnetic resonance imaging (fMRI) adult participants performed four Stroop task conditions in a block design (control, congruent, semantically incongruent, response incongruent). Here, we focussed on differences in activation between the two groups in two contrasts: (1) the presence of task-irrelevant information that conflicts at both the response and semantic level (response incongruent versus congruent); and (2) the presence of competing task-relevant information that confl icts at the response level only (response incongruent versus semantically incongruent). For the first contrast, comparisons between monolinguals (English) and the first language of bilinguals (Macedonian) revealed greater activation in the posterior regions of monolinguals, possibly indicative of a more elaborate stimulus evaluation process. For the second contrast, bilinguals showed less activation in anterior cingulate and prefrontal regions than monolinguals. As poor performance on the Stroop task has been found to be associated with greater activation in these two regions, we interpret this in light of earlier ideas regarding cognitive control and the advantages of bilingualism. That is, less effortful word-form processing might indicate that bilinguals are more effectively dealing with response conflict. Together the current findings suggest that learning two languages may modify the neural substrates engaged during tasks that rely on executive functioning.

Neural activity during Stroop colour-word task performance in late proficient bilinguals: a functional magnetic resonance imaging study

The aim of this study was to identify which neural substrates are engaged during manual Stroop task performance and compare the activation between 8 late proficient Macedonian-English bilinguals and 10 matched English monolinguals. During functional magnetic resonance imaging (fMRI) adult participants performed four Stroop task conditions in a block design (control, congruent, semantically incongruent, response incongruent). Here, we focussed on differences in activation between the two groups in two contrasts: (1) the presence of task-irrelevant information that conflicts at both the response and semantic level (response incongruent versus congruent); and (2) the presence of competing task-relevant information that confl icts at the response level only (response incongruent versus semantically incongruent). For the first contrast, comparisons between monolinguals (English) and the first language of bilinguals (Macedonian) revealed greater activation in the posterior regions of monolinguals, possibly indicative of a more elaborate stimulus evaluation process. For the second contrast, bilinguals showed less activation in anterior cingulate and prefrontal regions than monolinguals. As poor performance on the Stroop task has been found to be associated with greater activation in these two regions, we interpret this in light of earlier ideas regarding cognitive control and the advantages of bilingualism. That is, less effortful word-form processing might indicate that bilinguals are more effectively dealing with response conflict. Together the current findings suggest that learning two languages may modify the neural substrates engaged during tasks that rely on executive functioning.(AU)