title: Speech facilitation by left inferior frontal cortex stimulation.
abstract: Electrophysiological studies in humans and animals suggest that noninvasive neurostimulation methods such as transcranial direct current stimulation (tDCS) can elicit long-lasting [1], polarity-dependent [2] changes in neocortical excitability. Application of tDCS can have significant and selective behavioral consequences that are associated with the cortical location of the stimulation electrodes and the task engaged during stimulation [3-8]. However, the mechanism by which tDCS affects human behavior is unclear. Recently, functional magnetic resonance imaging (fMRI) has been used to determine the spatial topography of tDCS effects [9-13], but no behavioral data were collected during stimulation. The present study is unique in this regard, in that both neural and behavioral responses were recorded using a novel combination of left frontal anodal tDCS during an overt picture-naming fMRI study. We found that tDCS had significant behavioral and regionally specific neural facilitation effects. Furthermore, faster naming responses correlated with decreased blood oxygen level-dependent (BOLD) signal in Broca's area. Our data support the importance of Broca's area within the normal naming network and as such indicate that Broca's area may be a suitable candidate site for tDCS in neurorehabilitation of anomic patients, whose brain damage spares this region.
authors.affiliation: Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AR, UK. rachel.holland@ucl.ac.uk
authors.forename: Rachel
authors.initials: R
authors.lastname: Holland
authors.forename: Alex P
authors.initials: AP
authors.lastname: Leff
authors.forename: Oliver
authors.initials: O
authors.lastname: Josephs
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Galea
authors.forename: Mahalekshmi
authors.initials: M
authors.lastname: Desikan
authors.forename: Cathy J
authors.initials: CJ
authors.lastname: Price
authors.forename: John C
authors.initials: JC
authors.lastname: Rothwell
authors.forename: Jennifer
authors.initials: J
authors.lastname: Crinion
mesh_terms: D000368:Aged; D000818:Animals; D001519:Behavior / Q000502:physiology; D005260:Female; D005625:Frontal Lobe / Q000473:pathology / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D013060:Speech / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods