transcranial-direct-current-stimulation-simultaneous-functional

Transcranial Direct Current Stimulation and Simultaneous  Functional Magnetic Resonance Imaging

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses weak electrical currents administered to the scalp ...

Charité Universitätsmedizin

In the developing chicken embryo yolk sac vasculature, the expression of arterial identity genes requires arterial hemodynamic conditions. We hypothesize that arterial flow must provide a unique signal that is relevant for supporting arterial identity gene expression and is absent in veins. We analyzed factors related to flow, pressure and oxygenation in the chicken embryo vitelline vasculature in vivo. The best discrimination between arteries and veins was obtained by calculating the maximal pulsatile increase in shear rate relative to the time-averaged shear rate in the same vessel: the relative pulse slope index (RPSI). RPSI was significantly higher in arteries than veins. Arterial endothelial cells exposed to pulsatile shear in vitro augmented arterial marker expression as compared with exposure to constant shear. The expression of Gja5 correlated with arterial flow patterns: the redistribution of arterial flow provoked by vitelline artery ligation resulted in flow-driven collateral arterial network formation and was associated with increased expression of Gja5. In situ hybridization in normal and ligation embryos confirmed that Gja5 expression is confined to arteries and regulated by flow. In mice, Gja5 (connexin 40) was also expressed in arteries. In the adult, increased flow drives arteriogenesis and the formation of collateral arterial networks in peripheral occlusive diseases. Genetic ablation of Gja5 function in mice resulted in reduced arteriogenesis in two occlusion models. We conclude that pulsatile shear patterns may be central for supporting arterial identity, and that arterial Gja5 expression plays a functional role in flow-driven arteriogenesis.

Pulsatile shear and Gja5 modulate arterial identity and remodeling events during flow-driven arteriogenesis.

Excitatory anodal transcranial direct current stimulation (atDCS) can improve human cognitive functions, but neural underpinnings of its mode of action remain elusive. In a cross-over placebo ("sham") controlled study we used functional magnetic resonance imaging (fMRI) to investigate neurofunctional correlates of improved language functions induced by atDCS over a core language area, the left inferior frontal gyrus (IFG). Intrascanner transcranial direct current stimulation-induced changes in overt semantic word generation assessed behavioral modulation; task-related and task-independent (resting-state) fMRI characterized language network changes. Improved word-retrieval during atDCS was paralleled by selectively reduced task-related activation in the left ventral IFG, an area specifically implicated in semantic retrieval processes. Under atDCS, resting-state fMRI revealed increased connectivity of the left IFG and additional major hubs overlapping with the language network. In conclusion, atDCS modulates endogenous low-frequency oscillations in a distributed set of functionally connected brain areas, possibly inducing more efficient processing in critical task-relevant areas and improved behavioral performance.

Electrical brain stimulation improves cognitive performance by modulating functional connectivity and task-specific activation.

Post-stroke infections are the most important complications after acute stroke, accounting for almost 20% of in-hospital deaths and poor functional outcomes at discharge. Little is known about long-term effects of post-stroke infections on outcome. Here, we studied the impact of infections on long-term outcome in 64 patients which had suffered from severe middle cerebral artery infarction. Mean follow-up time in the survivors was 6.5 ± 0.9 years. Structured telephone interviews were performed to assess the patients' current functional outcome. Where re-contacting was not successful, vital status of the patients was requested at the registration office of Berlin. Multiple logistic regression analysis identified three independent risk factors associated with mortality: infections within the first 11 days after stroke, age>64 years, and female sex. Among surviving patients, functional outcome measured by Barthel Index was influenced by infections and immunocompetence measured by levels of monocytic HLA-DR expression on day 3 after stroke. In conclusion, the occurrence of post-stroke infections is the most important predictor of poor long-term outcome in this cohort of patients. Our observation warrants prospective trials on prevention or early treatment of post-stroke infections in order to improve long-term outcome after stroke.

Impact of infections on long-term outcome after severe middle cerebral artery infarction.

About one third of early deaths and poor outcomes after acute stroke are caused by potentially preventable stroke-associated complications, especially infections. Early identification of patients at high risk of infections and poor prognosis with biomarkers might help to initiate adequate therapies and guide treatment decisions. Acute injury of the central nervous system, including stroke, disturbs the normally well-balanced interplay between the sympathetic nervous system and the immune system, thereby impairing the antibacterial immune response in stroke patients. Changes in immune and stress markers, for example a reduction in HLA-DR expression on monocytes or an increase in serum catecholamine levels, occur very early after stroke onset, explain the high susceptibility of stroke patients to bacterial infections, and are predictive of infectious complications occurring up to 2 weeks after stroke. Outcome prediction is of utmost importance for decision-making in stroke units as well as in neurological intensive care units. However, to date the accuracy of outcome prediction by physicians and clinical scoring systems is only moderate. So far, only two blood-based biomarkers have been identified as independent predictors of outcome and mortality after stroke: the stress marker copeptin and midregional pro-atrial natriuretic peptide. Careful evaluation of prognostic markers is needed to prevent the occurrence of self-fulfilling prophecy.

Predicting post-stroke infections and outcome with blood-based immune and stress markers.

Stroke-associated pneumonia is one of the most common causes of poor outcome in stroke patients. Clinical signs and laboratory parameters of stroke-associated infections are often inconclusive. Biomarkers may help to identify stroke patients at high risk for pneumonia and to guide physicians in an early antibiotic treatment, thereby improving stroke outcome.

STRoke Adverse outcome is associated WIth NoSocomial Infections (STRAWINSKI): procalcitonin ultrasensitive-guided antibacterial therapy in severe ischaemic stroke patients - rationale and protocol for a randomized controlled trial.

Current assessment of visual neglect involves paper-and-pencil tests or computer-based tasks. Both have been criticised because of their lack of ecological validity as target stimuli can only be presented in a restricted visual range. This study examined the user-friendliness and diagnostic strength of a new "Circle-Monitor" (CM), which enlarges the range of the peripersonal space, in comparison to a standard paper-and-pencil test (Neglect-Test, NET).

Article	Year
Pulsatile shear and Gja5 modulate arterial identity and remodeling events during flow-driven arteriogenesis. Development (Cambridge, England)\| PubMed ID: 20530546	2010
Electrical brain stimulation improves cognitive performance by modulating functional connectivity and task-specific activation. The Journal of neuroscience : the official journal of the Society for Neuroscience\| PubMed ID: 22302824	2012
Impact of infections on long-term outcome after severe middle cerebral artery infarction. Journal of the neurological sciences\| PubMed ID: 22682764	2012
Predicting post-stroke infections and outcome with blood-based immune and stress markers. Cerebrovascular diseases (Basel, Switzerland)\| PubMed ID: 22710977	2012
STRoke Adverse outcome is associated WIth NoSocomial Infections (STRAWINSKI): procalcitonin ultrasensitive-guided antibacterial therapy in severe ischaemic stroke patients - rationale and pr... International journal of stroke : official journal of the International Stroke Society\| PubMed ID: 22925000	2013
A circle-monitor for computerised assessment of visual neglect in peripersonal space. PloS one\| PubMed ID: 24349387	2013

Lena Ulm

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