title: Transcranial brain stimulation: closing the loop between brain and stimulation.
abstract: To discuss recent strategies for boosting the efficacy of noninvasive transcranial brain stimulation to improve human brain function.
  
  
  
  Recent research exposed substantial intra- and inter-individual variability in response to plasticity-inducing transcranial brain stimulation. Trait-related and state-related determinants contribute to this variability, challenging the standard approach to apply stimulation in a rigid, one-size-fits-all fashion. Several strategies have been identified to reduce variability and maximize the plasticity-inducing effects of noninvasive transcranial brain stimulation. Priming interventions or paired associative stimulation can be used to 'standardize' the brain-state and hereby, homogenize the group response to stimulation. Neuroanatomical and neurochemical profiling based on magnetic resonance imaging and spectroscopy can capture trait-related and state-related variability. Fluctuations in brain-states can be traced online with functional brain imaging and inform the timing or other settings of transcranial brain stimulation. State-informed open-loop stimulation is aligned to the expression of a predefined brain state, according to prespecified rules. In contrast, adaptive closed-loop stimulation dynamically adjusts stimulation settings based on the occurrence of stimulation-induced state changes.
  
  
  
  Approaches that take into account trait-related and state-related determinants of stimulation-induced plasticity bear considerable potential to establish noninvasive transcranial brain stimulation as interventional therapeutic tool.
authors.affiliation: aDanish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre bDepartment of Electrical Engineering, Technical University of Denmark, Kgs. Lyngby cDepartment of Neurology, Copenhagen University Hospital Bispebjerg, Copenhagen, Denmark.
authors.forename: Anke
authors.initials: A
authors.lastname: Karabanov
authors.forename: Axel
authors.initials: A
authors.lastname: Thielscher
authors.forename: Hartwig Roman
authors.initials: HR
authors.lastname: Siebner
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000528:radiation effects; D001927:Brain Diseases / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D009473:Neuronal Plasticity / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*