title: Transcranial magnetic stimulation (TMS) inhibits cortical dendrites.
abstract: One of the leading approaches to non-invasively treat a variety of brain disorders is transcranial magnetic stimulation (TMS). However, despite its clinical prevalence, very little is known about the action of TMS at the cellular level let alone what effect it might have at the subcellular level (e.g. dendrites). Here, we examine the effect of single-pulse TMS on dendritic activity in layer 5 pyramidal neurons of the somatosensory cortex using an optical fiber imaging approach. We find that TMS causes GABAB-mediated inhibition of sensory-evoked dendritic Ca(2+) activity. We conclude that TMS directly activates fibers within the upper cortical layers that leads to the activation of dendrite-targeting inhibitory neurons which in turn suppress dendritic Ca(2+) activity. This result implies a specificity of TMS at the dendritic level that could in principle be exploited for investigating these structures non-invasively.
authors.affiliation: Neurocure Cluster of Excellence, Humboldt University, Berlin, Germany.|Physiologisches Institut, Universität Bern, Bern, Switzerland.|Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia.
authors.forename: Sean C
authors.initials: SC
authors.lastname: Murphy
authors.affiliation: Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia.
authors.forename: Lucy M
authors.initials: LM
authors.lastname: Palmer
authors.affiliation: Neurology and Neurorehabilitation Centre, Luzerner Kantonsspital, Luzern, Switzerland.|Departments of Neurology, University Hospital, Inselspital, University of Bern, Bern, Switzerland.|Department of Clinical Research, University Hospital, Inselspital, University of Bern, Bern, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Nyffeler
authors.affiliation: Departments of Neurology, University Hospital, Inselspital, University of Bern, Bern, Switzerland.|Department of Clinical Research, University Hospital, Inselspital, University of Bern, Bern, Switzerland.
authors.forename: René M
authors.initials: RM
authors.lastname: Müri
authors.affiliation: Neurocure Cluster of Excellence, Humboldt University, Berlin, Germany.|Physiologisches Institut, Universität Bern, Bern, Switzerland.
authors.forename: Matthew E
authors.identifier: http://orcid.org/0000-0001-9799-2656
authors.initials: ME
authors.lastname: Larkum
mesh_terms: D000818:Animals; D020013:Calcium Signaling; D003712:Dendrites / Q000502:physiology*; D005260:Female; D059330:GABAergic Neurons / Q000528:radiation effects*; D008297:Male; D061848:Optical Imaging; D017966:Pyramidal Cells / Q000528:radiation effects*; D017208:Rats, Wistar; D013003:Somatosensory Cortex / Q000528:radiation effects*; D050781:Transcranial Magnetic Stimulation
keywords: GABAB inhibition; dendritic integration; in vivo; neuroscience; rat; transcranial magnetic stimulation