title: Assessment of anodal and cathodal transcranial direct current stimulation (tDCS) on MMN-indexed auditory sensory processing.
abstract: Transcranial direct current stimulation (tDCS) is a non-invasive form of brain stimulation which uses a very weak constant current to temporarily excite (anodal stimulation) or inhibit (cathodal stimulation) activity in the brain area of interest via small electrodes placed on the scalp. Currently, tDCS of the frontal cortex is being used as a tool to investigate cognition in healthy controls and to improve symptoms in neurological and psychiatric patients. tDCS has been found to facilitate cognitive performance on measures of attention, memory, and frontal-executive functions. Recently, a short session of anodal tDCS over the temporal lobe has been shown to increase auditory sensory processing as indexed by the Mismatch Negativity (MMN) event-related potential (ERP). This preliminary pilot study examined the separate and interacting effects of both anodal and cathodal tDCS on MMN-indexed auditory pitch discrimination. In a randomized, double blind design, the MMN was assessed before (baseline) and after tDCS (2mA, 20min) in 2 separate sessions, one involving 'sham' stimulation (the device is turned off), followed by anodal stimulation (to temporarily excite cortical activity locally), and one involving cathodal stimulation (to temporarily decrease cortical activity locally), followed by anodal stimulation. Results demonstrated that anodal tDCS over the temporal cortex increased MMN-indexed auditory detection of pitch deviance, and while cathodal tDCS decreased auditory discrimination in baseline-stratified groups, subsequent anodal stimulation did not significantly alter MMN amplitudes. These findings strengthen the position that tDCS effects on cognition extend to the neural processing of sensory input and raise the possibility that this neuromodulatory technique may be useful for investigating sensory processing deficits in clinical populations.
authors.affiliation: School of Psychology, University of Ottawa, Ottawa, Canada; University of Ottawa, Institute of Mental Health Research, Ottawa, Canada. Electronic address: danielle.impey@theroyal.ca.
authors.forename: Danielle
authors.initials: D
authors.lastname: Impey
authors.affiliation: School of Psychology, University of Ottawa, Ottawa, Canada; University of Ottawa, Institute of Mental Health Research, Ottawa, Canada. Electronic address: sara.delasalle@theroyal.ca.
authors.forename: Sara
authors.initials: S
authors.lastname: de la Salle
authors.affiliation: School of Psychology, University of Ottawa, Ottawa, Canada; University of Ottawa, Institute of Mental Health Research, Ottawa, Canada. Electronic address: verner.knott@theroyal.ca.
authors.forename: Verner
authors.initials: V
authors.lastname: Knott
mesh_terms: D000293:Adolescent; D000328:Adult; D001303:Auditory Cortex / Q000502:physiology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D008297:Male; D010865:Pilot Projects; D010897:Pitch Discrimination / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D055815:Young Adult
keywords: Auditory sensory discrimination; Event-related potentials (ERPs); Mismatch negativity (MMN); NMDA receptors; Transcranial direct current stimulation (tDCS)