title: Rhythmic TMS causes local entrainment of natural oscillatory signatures.
abstract: BACKGROUND
  Neuronal elements underlying perception, cognition, and action exhibit distinct oscillatory phenomena, measured in humans by electro- or magnetoencephalography (EEG/MEG). So far, the correlative or causal nature of the link between brain oscillations and functions has remained elusive. A compelling demonstration of causality would primarily generate oscillatory signatures that are known to correlate with particular cognitive functions and then assess the behavioral consequences. Here, we provide the first direct evidence for causal entrainment of brain oscillations by transcranial magnetic stimulation (TMS) using concurrent EEG.
  
  
  RESULTS
  We used rhythmic TMS bursts to directly interact with an MEG-identified parietal α-oscillator, activated by attention and linked to perception. With TMS bursts tuned to its preferred α-frequency (α-TMS), we confirmed the three main predictions of entrainment of a natural oscillator: (1) that α-oscillations are induced during α-TMS (reproducing an oscillatory signature of the stimulated parietal cortex), (2) that there is progressive enhancement of this α-activity (synchronizing the targeted, α-generator to the α-TMS train), and (3) that this depends on the pre-TMS phase of the background α-rhythm (entrainment of natural, ongoing α-oscillations). Control conditions testing different TMS burst profiles and TMS-EEG in a phantom head confirmed specificity of α-boosting to the case of synchronization between TMS train and neural oscillator.
  
  
  CONCLUSIONS
  The periodic electromagnetic force that is generated during rhythmic TMS can cause local entrainment of natural brain oscillations, emulating oscillatory signatures activated by cognitive tasks. This reveals a new mechanism of online TMS action on brain activity and can account for frequency-specific behavioral TMS effects at the level of biologically relevant rhythms.
authors: Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of Glasgow, Glasgow G12 8QB, UK. gregor.thut@glasgow.ac.uk
authors: Gregor
authors: G
authors: Thut
authors: Domenica
authors: D
authors: Veniero
authors: Vincenzo
authors: V
authors: Romei
authors: Carlo
authors: C
authors: Miniussi
authors: Philippe
authors: P
authors: Schyns
authors: Joachim
authors: J
authors: Gross
mesh_terms: D000328:Adult; D000513:Alpha Rhythm; D000704:Analysis of Variance; D001288:Attention; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015225:Magnetoencephalography; D008297:Male; D009778:Occipital Lobe / Q000502:physiology*; D010296:Parietal Lobe / Q000502:physiology*; D010507:Periodicity; D010775:Photic Stimulation; D050781:Transcranial Magnetic Stimulation; D014795:Visual Pathways; D014796:Visual Perception