P 49. Modulation of spontaneous and TMS-evoked alpha oscillations by top-down visual attention

Autor: Gregor Thut, Ole Jensen, Til Ole Bergmann, Jim Don Herring
Rok vydání: 2013
Předmět:
Zdroj: Clinical Neurophysiology. 124:e87
ISSN: 1388-2457
DOI: 10.1016/j.clinph.2013.04.127
Popis: Introduction Simultaneous transcranial magnetic stimulation (TMS) and electroencephalography (EEG) allows the direct assessment of cortico-thalamic responsiveness by TMS-evoked EEG potentials (TEPs). Notably, the frequency composition of TEPs corresponds to the dominant spontaneous oscillation at the respective stimulation site, e.g. ′alpha′ in the visual cortex (Rosanova et al., J Neurosci 2009). Furthermore, TEPs change dramatically with shifts in neuromodulatory levels during sleep (Massimini et al., Science 2005; Bergmann et al., J Neurosci 2012), suggesting that both are generated by the same neuronal mechanisms. Indeed, rhythmic TMS of the parieto-occipital cortex can mimic alpha band (8–12 Hz) oscillations in the EEG (Thut et al., Curr Biol 2011) as well as their known impact on perceptual performance (Romei et al., J Neurosci 2010) due to gating by inhibition (Jensen et al., TICS 2012). However, does the alpha-like TEP as response to visual cortex stimulation actually resemble spontaneous alpha oscillations or rather visual evoked potentials (VEPs)? Importantly, VEPs are amplified by visual attention (Rajagovindan and Ding, J Cog Neurosci, 2011), whereas spontaneous alpha oscillations are suppressed (Foxe et al., Neurorep 1998; Fu et al., Cog Brain Res 2001). Objectives To test the similarity between transcranially evoked and spontaneous alpha oscillations, we currently investigate whether they show comparable responses to covert shifts in attention, i.e., decrease and increase in amplitude when attending the visual and auditory modality, respectively (Foxe and Snyder, Front Psychol 2011). Methods Here, we measure TEPs my means of simultaneously applied 61-channel EEG and neuronavigated single-pulse TMS to the visual cortex while subjects attend to either visual or auditory noise patterns in order to detect slight contrast modulations. Since auditory stimuli have been shown to evoke an alpha-like response in the visual cortex (Romei, Gross and Thut, Curr Biol 2012), we use a constant stream of auditory masking noise as well as sham TMS to control for these effects. Results and conclusion Preliminary results suggest that the TMS-evoked alpha oscillation is in fact modulated by top-down visual attention in analogy to spontaneous alpha oscillations, suggesting that both are generated by the same underlying neural mechanisms.
Databáze: OpenAIRE
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