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Transcranial alternating current stimulation (tACS) has emerged as a promising tool for manipulating ongoing brain oscillations. While previous studies demonstrated frequency-specific effects of tACS on diverse cognitive functions, its effect on neural activity remains poorly understood. Here we asked how tACS modulates regional fMRI blood oxygenation level dependent (BOLD) signal as a function of frequency, current strength, and task condition. TACS was applied over the posterior cortex of healthy human subjects while the BOLD signal was measured during rest or task conditions (visual perception, passive video viewing and motor task). TACS was applied in a blockwise manner at different frequencies (10, 16, 60 and 80 Hz). The strongest tACS effects on BOLD activity were observed with stimulation at alpha (10 Hz) and beta (16 Hz) frequency bands, while effects of tACS at the gamma range were rather modest. Specifically, we found that tACS at 16 Hz induced BOLD activity increase in fronto-parietal areas. Overall, tACS effects varied as a function of frequency and task, and were predominantly seen in regions that were not activated by the task. Also, the modulated regions were poorly predicted by current density modeling studies. Taken together, our results suggest that tACS does not necessarily exert its strongest effects in regions below the electrodes and that region specificity might be achieved with tACS due to varying susceptibility of brain regions to entrain to a given frequency., (© 2015 The Authors. Human Brain Mapping Published by Wiley Periodicals, Inc.)

In Tourette syndrome (TS), not only the tics but also the findings on deficits in motor performance indicate motor system alterations. But our knowledge about the pathophysiology of the motor system in TS is still limited. To better understand the neuronal correlates of motor performance in TS, 19 treatment-naïve boys [age 12.5 (SD 1.4) years] with TS without comorbid symptomatology were compared to an age-matched healthy control group [n = 16; age 12.9 (SD 1.6) years] in regard to brain activation during right-hand index finger tapping by means of functional magnetic resonance imaging. Group differences were found mainly in the left (contralateral) precentral gyrus, which was less activated in boys suffering from TS and in caudate nucleus as well as in medial prefrontal cortex, which was more activated compared to healthy boys. These results show that even in the first years after the onset of the disorder, an altered brain network of motor performance is recruited. These alterations in brain regions frequently associated with TS are probably based on functional changes, which are discussed in terms of early compensatory mechanisms of the motor execution network., (Copyright © 2011 Wiley Periodicals, Inc.)

Background and Purpose: Studies addressing the diagnostic relevance of anti-Borrelia burgdorferi (BB) serum antibodies in patients with non-specific symptoms and suspected chronic Lyme neuroborreliosis (LNB) are scarce., Methods: In this study, we enrolled within 1 year 122 patients with suspected chronic LNB. One hundred and fourteen patients had previously tested positive for BB. All patients had previously received antibiotic treatment. Each patient received a clinical examination and measurement of BB-specific antibodies. The diagnosis of neuroborreliosis was made according to the national guidelines of the German Society of Neurology. Nine patients had acute borreliosis. One of the nine met the criteria of acute LNB. Of the remaining 113 patients, 85 patients underwent a lumbar puncture. Ten seronegative subjects without lumbar puncture were also considered. In 61.8% of these 95 patients the quality of life, of sleep, mood, and anxiety were assessed., Results: Of 95 patients, 25.3% had symptoms without a somatic cause or evidence of borreliosis, 38.9% had a well-defined illness unrelated to BB infection, and 29.5% suffered from symptoms without a detectable somatic cause, displaying antibodies against BB. Six patients were grouped as post-LNB syndrome. Most common symptoms in all categories were arthralgia, myalgia, dysaesthesia, depressive mood and chronic fatigue., Conclusion: Patients with persistent symptoms with elevated serum antibodies against BB but without signs of cerebrospinal fluid inflammation require further diagnostic examinations to exclude ongoing infection and to avoid co-infections and other treatable conditions (e.g. autoimmune diseases). One patient with acute LNB, who was treated with ceftriaxone for 3 weeks suffered from LNB with new headaches and persistent symptoms 6 months later. These data should encourage further studies with new experimental parameters., (© 2010 The Author(s). European Journal of Neurology © 2010 EFNS.)