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Using transcranial alternating current stimulation (tACS) to improve visuospatial working memory (vsWM) has received considerable attention over the past few years. However, fundamental issues remain, such as the optimal frequency, the generality of behavioral effects, and the anatomical specificity of stimulation.Here we examined the effects of two theory-driven tACS protocols for improving vsWM on behavioral and electroencephalogram (EEG) measures.Twenty adults each completed 3 HD-tACS conditions (Tuned, Slow, and Sham) on two separate days. The Tuned condition refers to a situation in which the frequency of tACS is tuned to individual theta peak measured during a vsWM task. By contrast, the frequency was fixed to 4 Hz in the Slow condition. A high-definition tACS was deployed to target smaller frontal and parietal regions for increasing their phase-locking values. During each tACS condition, participants performed vsWM, mental rotation (MR), and arithmetic tasks. Resting-state EEG (rs-EEG) was recorded before and after each condition.Compared with Sham, Tuned but not Slow improved both vsWM and MR but not arithmetics. The rs-EEG recording showed an increased fronto-parietal synchrony for Tuned, and this increase in synchronicity was correlated with the behavioral improvement. A follow-up study showed no behavioral improvement in Tuned with an anti-phase setting.We provide the first evidence that simulating right fronto-parietal network with the tuned frequency increases the interregional synchronicity and improves performance on two spatial tasks. The results provide insight into the structure of spatial abilities as well as suggestions for stimulating the fronto-parietal network.

BACKGROUND Adaptive servo-ventilation (ASV) (AutoSetCS, ResMed) is a novel non-invasive ventilation modality for the treatment of Cheyne-Stokes-Respiration (CSR) in patients with heart failure. This study aimed to investigate the effect of ASV on sleep disordered breathing (SDB), afternoon nap duration, urine voidings, and quality of life. METHODS 11 patients with CSR due to heart failure (EF < 40 %) were treated with ASV for a period of 6 weeks. Apnea-Hypopnoe-Index (AHI), Arousalindex (AI), duration of afternoon nap, number of voidings, and heart specific quality of life were assessed before and at the end of the treatment period. RESULTS The average usage time of ASV was 5.8 +/- 2.1/h per day. With ASV the AHI was reduced from 48.2 +/- 11.6 to 6.4 +/- 8.3/h (p < 0.001) and the AI from 33.9 +/- 12.5 to 18.4 +/- 9.3 /h (p < 0.05). The afternoon nap duration was significantly less (1.4 +/- 0.6 vs. 0.7 +/- 0.4 hours per day; p = 0.004) as was the number of nocturnal voidings (2.9 +/- 0.7 vs. 1.1 +/- 0.3 per night; p = 0.007). There was a significant improvement in heart specific quality of life as measured with the Minnesota Living with heart failure questionnaire (43.5 +/- 21.1 vs. 27.6 +/- 15.7 (p = 0.02). CONCLUSION ASV is well tolerated and improves SDB and quality of life of patients with heart failure with CSR.

In order to analyze the epileptogenic mechanisms of caffeine and related xanthines, putative effects of these drugs were studied on adenosine receptors of CA3 neurons in hippocampal slices. Epileptogenic concentrations of different xanthine derivatives strongly correlated with their affinities for the inhibitory A1 adenosine receptor subtype. The A1 receptor agonists adenosine and R-PIA reversibly depressed xanthine-induced epileptic activity without effects on the resting membrane potential or on spontaneously occurring action potentials. These findings suggest that the epileptogenic potency of xanthines is primarily due to the blockade of the A1 receptors through an abnormal rise of intracellular cAMP and to the excessive transmembrane calcium fluxes underlying paroxysmal depolarization shifts.

In order to analyze the elementary mechanisms underlying caffeine-induced epileptiform discharges, hippocampal slices of guinea pigs were exposed to this drug. When the bath concentration of caffeine exceeded 0.2 mM, periodically occurring paroxysmal depolarizations (PD) in CA3 neurons appeared. They were accompanied by declines of extracellular free calcium concentration and were suppressed by the organic calcium antagonists verapamil and flunarizine. PD-like fluctuations of the membrane potential could be evoked also in CA3 neurons functionally isolated by tetrodotoxin (TTX). The observations indicate that caffeine-induced PD are generated endogenously and that transmembranous calcium currents contribute to these mechanisms.