title: Baseline effects of transcranial direct current stimulation on glutamatergic neurotransmission and large-scale network connectivity.
abstract: Transcranial direct current stimulation (tDCS) modulates glutamatergic neurotransmission and can be utilized as a novel treatment intervention for a multitude of populations. However, the exact mechanism by which tDCS modulates the brain׳s neural architecture, from the micro to macro scales, have yet to be investigated. Using a within-subjects design, resting-state functional magnetic resonance imaging (rs-fMRI) and proton magnetic resonance spectroscopy ((1)H MRS) were performed immediately before and after the administration of anodal tDCS over right parietal cortex. Group independent component analysis (ICA) was used to decompose fMRI scans into 75 brain networks, from which 12 resting-state networks were identified that had significant voxel-wise functional connectivity to anatomical regions of interest. (1)H MRS was used to obtain estimates of combined glutamate and glutamine (Glx) concentrations from bilateral intraparietal sulcus. Paired sample t-tests showed significantly increased Glx under the anodal electrode, but not in homologous regions of the contralateral hemisphere. Increases of within-network connectivity were observed within the superior parietal, inferior parietal, left frontal-parietal, salience and cerebellar intrinsic networks, and decreases in connectivity were observed in the anterior cingulate and the basal ganglia (p<0.05, FDR-corrected). Individual differences in Glx concentrations predicted network connectivity in most of these networks. The observed relationships between glutamatergic neurotransmission and network connectivity may be used to guide future tDCS protocols that aim to target and alter neuroplastic mechanisms in healthy individuals as well as those with psychiatric and neurologic disorders.
authors.affiliation: Psychology Clinical Neuroscience Center, The University of New Mexico, Albuquerque, NM, USA; Department of Psychology, The University of New Mexico, NM, USA; The Mind Research Network, Albuquerque, NM, USA; Department of Psychiatry, The University of New Mexico School of Medicine, Albuquerque, NM, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hunter
authors.affiliation: Psychology Clinical Neuroscience Center, The University of New Mexico, Albuquerque, NM, USA; Department of Psychology, The University of New Mexico, NM, USA; The Mind Research Network, Albuquerque, NM, USA.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Coffman
authors.affiliation: The Mind Research Network, Albuquerque, NM, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Gasparovic
authors.affiliation: The Mind Research Network, Albuquerque, NM, USA; Department of Psychiatry, The University of New Mexico School of Medicine, Albuquerque, NM, USA; Department of Neurosciences, The University of New Mexico, Albuquerque, NM, USA; Department of Electrical and Computer Engineering, The University of New Mexico, Albuquerque, NM, USA.
authors.forename: Vince D
authors.initials: VD
authors.lastname: Calhoun
authors.affiliation: Psychology Clinical Neuroscience Center, The University of New Mexico, Albuquerque, NM, USA; Department of Psychology, The University of New Mexico, NM, USA; The Mind Research Network, Albuquerque, NM, USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Trumbo
authors.affiliation: Psychology Clinical Neuroscience Center, The University of New Mexico, Albuquerque, NM, USA; Department of Psychology, The University of New Mexico, NM, USA; The Mind Research Network, Albuquerque, NM, USA; Department of Neurosciences, The University of New Mexico, Albuquerque, NM, USA. Electronic address: vclark@unm.edu.
authors.forename: Vincent P
authors.initials: VP
authors.lastname: Clark
mesh_terms: D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods; D005260:Female; D018698:Glutamic Acid / Q000032:analysis / Q000378:metabolism; D005973:Glutamine / Q000032:analysis / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009415:Nerve Net / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult
chemical_list: D005973:Glutamine; D018698:Glutamic Acid
keywords: Functional network connectivity (FNC); Glutamine–glutamate (Glx); Independent component analysis (ICA); Magnetic resonance spectroscopy (MRS); Parietal lobe; Resting-state functional magnetic resonance imaging (rs-fMRI); Transcranial direct current stimulation (tDCS)