Neuroscience Letters 419 (2007) 162–167 The effects of 10 Hz repetitive transcranial magnetic stimulation on resting EEG power spectrum in healthy subjects Inga Griˇ skova a,b,∗ , Osvaldas Rukˇ s˙ enas a , Kastytis Dapˇ sys a,c , Sabine Herpertz b , Jacqueline H ¨ oppner b a Department of Biochemistry and Biophysics, Vilnius University, Vilnius, Lithuania b Department of Psychiatry and Psychotherapy, Centre of Nervous Disease, University of Rostock, Rostock, Germany c Department of Electrophysiological Research and Treatment Methods, Republican Vilnius Psychiatric Hospital, Vilnius, Lithuania Received 19 December 2006; received in revised form 7 February 2007; accepted 16 April 2007 Abstract 10Hz rTMS over the left prefrontal cortex may be useful in the treatment of depressive disorders. However, the effects of 10Hz rTMS applied in potentially effective doses on electroencephalographic activity are not well studied. Using EEG, we aimed to investigate the neurobiological effects of the 10 Hz rTMS set of parameters currently used for depression treatment in a sample of healthy subjects. In 18 healthy subjects, either 10 Hz real rTMS or sham stimulation were given in a crossover design. Real rTMS stimulation was carried out with an intensity of 110% of motor threshold (MT) over the left dorsolateral prefrontal cortex. For the sham condition, the coil was angled over a parietotemporal position and the intensity was reduced to 90% of MT. EEG recordings were taken before and after a single rTMS session. EEG power spectrum was extracted using the complex demodulation method and changes in power were evaluated statistically. Real 10 Hz rTMS induced an overall increase in delta power. This increase prevailed throughout the sample, whereas effects on the power of the alpha, beta and theta EEG bands were highly variable. Sham stimulation had no substantial effects on the EEG power spectrum. Furthermore, no changes in EEG asymmetry were detected. Real 10 Hz rTMS applied at 2000 stimuli and 110% intensity may induce significant changes in resting EEG in healthy subjects. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Transcranial magnetic stimulation; Electroencephalogram; Left dorsolateral prefrontal cortex In the last few years, the repetitive transcranial magnetic stim- ulation (rTMS) method, which is based on the application of magnetic pulses to the intact head, has emerged as a possible therapeutic modality in several neuro-psychiatric disorders [5], and especially in affective disorders [6]. The use of rTMS in therapeutic paradigms is based on the repetitive application of pulses, usually at a frequency of 1Hz or greater. The major- ity of rTMS studies in depressive patients used high frequency (10–20 Hz) rTMS over the left dorsolateral prefrontal cortex (LDLPFC) [5]. No consensus has yet been reached on the therapeutic efficacy of rTMS, although it has been established that factors such as repetition frequency, stimulation site, stimulation intensity and number of stimuli applied are important [14]. Various combina- ∗ Corresponding author at: Department of Biochemistry and Biophysics, Vil- nius University, ˇ Ciurlionio 21,Vilnius LT-03101, Lithuania. Tel.: +370 52398218; fax: +370 52398216. E-mail address: inga.griskova@gf.vu.lt (I. Griˇ skova). tions of these parameters produce a great number of stimulation protocols. It is reasonable to expect that different sets of stimula- tion parameters might produce different therapeutic responses. So far, the pathophysiological and therapeutic mechanisms of rTMS have not been fully clarified. Electroencephalography (EEG) is a well-known and widely used technique for the visualization of brain activity. It has been suggested that power spectrum might be used as a tool for assessing the effects of a specific stimulation protocol as well as for evaluating the physiological outcome of the stimulation [4]. However, only in two studies clinically applicable fast rTMS sets (20 Hz and 10 Hz) have been applied in a single stimulation pro- cedure to healthy subjects, with the effects on qEEG measures investigated [10,21]. Both studies failed to show any substan- tial longer-lasting effects on EEG power spectra, although the studies differed in terms of their aims, stimulation settings and methods of analysis. The aim of the current study was to investigate the effect of 10 Hz rTMS over LDLPFC in comparison to a sham stimulation 0304-3940/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2007.04.030