Article

Neurochemical effects of theta burst stimulation as assessed by magnetic resonance spectroscopy.

Centre for Functional Resonance Imaging of the Brain, University of Oxford, Oxford, United Kingdom.
Journal of Neurophysiology (Impact Factor: 3.04). 05/2009; 101(6):2872-7. DOI: 10.1152/jn.91060.2008
Source: PubMed

ABSTRACT Continuous theta burst stimulation (cTBS) is a novel transcranial stimulation technique that causes significant inhibition of synaptic transmission for <or=1 h when applied over the primary motor cortex (M1) in humans. Here we use magnetic resonance spectroscopy to define mechanisms mediating this inhibition by noninvasively measuring local changes in the cortical concentrations of gamma-aminobutyric acid (GABA) and glutamate/glutamine (Glx). cTBS to the left M1 led to an increase in GABA compared with stimulation at a control site without significant change in Glx. This direct evidence for increased GABAergic interneuronal activity is framed in terms of a new hypothesis regarding mechanisms underlying cTBS.

0 Bookmarks
 · 
116 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Transcranial magnetic stimulation (TMS) is a widely used tool for noninvasive modulation of brain activity, that is thought to interact primarily with excitatory and inhibitory neurotransmitter systems. Neurotransmitters such as glutamate and GABA can be measured by magnetic resonance spectoscopy (MRS). An important prerequisite for studying the relationship between MRS neurotransmitter levels and responses to TMS is that both modalities should examine the same regions of brain tissue. However, co-registration of TMS and MRS has been little studied to date. This study reports on a procedure for the co-registration and co-visualization of MRS and TMS, successfully localizing the hand motor cortex, as subsequently determined by its functional identification using TMS. Sixteen healthy subjects took part in the study; in 14 of 16 subjects, the TMS determined location of motor activity intersected the (2.5cm)(3) voxel selected for MRS, centered on the so called 'hand knob' of the precentral gyrus. It is concluded that MRS voxels placed according to established anatomical landmarks in most cases agree well with functional determination of the motor cortex by TMS. Reasons for discrepancies are discussed. Copyright © 2014. Published by Elsevier B.V.
    Journal of Neuroscience Methods 01/2015; · 1.96 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The developmental pathophysiology of autism spectrum disorders (ASD) is currently not fully understood. However, multiple lines of evidence suggest that the behavioral phenotype may result from dysfunctional inhibitory control over excitatory synaptic plasticity. Consistent with this claim, previous studies indicate that adults with Asperger's Syndrome show an abnormally extended modulation of corticospinal excitability following a train of repetitive transcranial magnetic stimulation (rTMS). As ASD is a developmental disorder, the current study aimed to explore the effect of development on the duration of modulation of corticospinal excitability in children and adolescents with ASD. Additionally, as the application of rTMS to the understanding and treatment of pediatric neurological and psychiatric disorders is an emerging field, this study further sought to provide evidence for the safety and tolerability of rTMS in children and adolescents with ASD. Corticospinal excitability was measured by applying single pulses of TMS to the primary motor cortex both before and following a 40 s train of continuous theta burst stimulation. 19 high-functioning males ages 9-18 with ASD participated in this study. Results from this study reveal a positive linear relationship between age and duration of modulation of rTMS after-effects. Specifically we found that the older participants had a longer lasting response. Furthermore, though the specific protocol employed typically suppresses corticospinal excitability in adults, more than one third of our sample had a paradoxical facilitatory response to the stimulation. Results support the safety and tolerability of rTMS in pediatric clinical populations. Data also support published theories implicating aberrant plasticity and GABAergic dysfunction in this population.
    Frontiers in Human Neuroscience 08/2014; 8:627. · 2.90 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Left and right dorsolateral prefrontal cortex (dlPFC) were recently found to be differentially affected by unilateral continuous theta-burst stimulation, reflected in an oppositional alteration of initial thinking time (ITT) in the Tower of London planning task. Here, we further explored this finding using bilateral transcranial direct current stimulation (tDCS) and simultaneous tracking of eye movements. Results revealed a decrease in ITT during concurrent cathodal tDCS of left dlPFC and anodal tDCS of right dlPFC. Eye-movement analyses showed that this facilitating tDCS effect was associated with the actual planning phase, thus reflecting a planning-specific impact of stimulation. For the reverse stimulation pattern of cathodal tDCS of right dlPFC and anodal tDCS of left dlPFC, an increase in gaze shifts was observed, without a significant impact on ITT. Taken together, these findings corroborate that enhanced planning performance can be obtained by boosting right dlPFC and dismantling the inhibitory impact of left dlPFC.
    Biological Psychology 08/2014; · 3.47 Impact Factor

Full-text (2 Sources)

Download
13 Downloads
Available from
Nov 17, 2014