Neurochemical Effects of Theta Burst Stimulation as Assessed by Magnetic Resonance Spectroscopy

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Abstract

Continuous theta burst stimulation (cTBS) is a novel transcranial stimulation technique that causes significant inhibition of synaptic transmission for ≤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 γ-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.

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Most cited references 43

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Simultaneous in vivo spectral editing and water suppression.

M Mescher, H. Merkle, J Kirsch … (1998)

Water suppression is typically performed in vivo by exciting the longitudinal magnetization in combination with dephasing, or by using frequency-selective coherence generation. MEGA, a frequency-selective refocusing technique, can be placed into any pulse sequence element designed to generate a Hahn spin-echo or stimulated echo, to dephase transverse water coherences with minimal spectral distortions. Water suppression performance was verified in vivo using stimulated echo acquisition mode (STEAM) localization, which provided water suppression comparable with that achieved with four selective pulses in 3,1-DRYSTEAM. The advantage of the proposed method was exploited for editing J-coupled resonances. Using a double-banded pulse that selectively inverts a J-coupling partner and simultaneously suppresses water, efficient metabolite editing was achieved in the point resolved spectroscopy (PRESS) and STEAM sequences in which MEGA was incorporated. To illustrate the efficiency of the method, the detection of gamma-aminobutyric acid (GABA) was demonstrated, with minimal contributions from macromolecules and overlying singlet peaks at 4 T. The estimated occipital GABA concentration was consistent with previous reports, suggesting that editing for GABA is efficient when based on MEGA at high field strengths.

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Localization of the motor hand area to a knob on the precentral gyrus. A new landmark.

T A Yousry, U D Schmid, H Alkadhi … (1997)

Using functional magnetic resonance imaging (fMRI) we have evaluated the anatomical location of the motor hand area. The segment of the precentral gyrus that most often contained motor hand function was a knob-like structure, that is shaped like an omega or epsilon in the axial plane and like a hook in the sagittal plane. On the cortical surface of cadaver specimens this precentral knob corresponded precisely to the characteristic 'middle knee' of the central sulcus that has been described by various anatomists in the last century. We were then able to show that this knob is a reliable landmark for identifying the precentral gyrus directly. We therefore conclude that neural elements involved in motor hand function are located in a characteristic 'precentral knob' which is a reliable landmark for identifying the precentral gyrus under normal and pathological conditions. It faces and forms the 'middle knee' of the central sulcus, is located just at the cross point between the precentral sulcus and the central sulcus, and is therefore also visible on the cortical surface.

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Responses to rapid-rate transcranial magnetic stimulation of the human motor cortex.

A. Pascual-Leone, J. Valls-Solé, E Wassermann … (1994)

We applied trains of focal, rapid-rate transcranial magnetic stimulation (rTMS) to the motor cortex of 14 healthy volunteers with recording of the EMG from the contralateral abductor pollicis brevis, extensor carpi radialis, biceps brachii and deltoid muscles. Modulation of the amplitude of motor evoked potentials (MEPs) produced in the target muscle during rTMS showed a pattern of inhibitory and excitatory effects which depended on the rTMS frequency and intensity. With the magnetic coil situated over the optimal scalp position for activating the abductor pollicis brevis, rTMS led to spread of excitation, as evident from the induction of progressively larger MEPs in the other muscles. The number of pulses inducing this spread of excitation decreased with increasing rTMS frequency and intensity. Latency of the MEPs produced in the other muscles during the spread of excitation was significantly longer than that produced by single-pulse TMS applied to the optimal scalp positions for their activation. The difference in MEP latency could be explained by a delay in intracortical conduction along myelinated cortico-cortical pathways. Following rTMS, a 3-4 min period of increased excitability was demonstrated by an increase in the amplitude of MEPs produced in the target muscles by single-pulse TMS. Nevertheless, repeated rTMS trains applied 1 min apart led to similar modulation of the responses and to spread of excitation after approximately the same number of pulses. This suggests that the spread might be due to the breakdown of inhibitory connections or the recruitment of excitatory pathways, whereas the post-stimulation facilitation may be due to a transient increase in the efficacy of excitatory synapses.

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Author and article information

Journal

Journal ID (nlm-ta): J Neurophysiol

Journal ID (publisher-id): jn

Title: Journal of Neurophysiology

Publisher: American Physiological Society

ISSN (Print): 0022-3077

ISSN (Electronic): 1522-1598

Publication date (Print): June 2009

Publication date (Electronic): 1 April 2009

Publication date PMC-release: 1 June 2010

Volume: 101

Issue: 6

Pages: 2872-2877

Affiliations

[1 ]Centre for Functional Resonance Imaging of the Brain and [2 ]Department of Clinical Neurology, University of Oxford, Oxford; [3 ]Biological Imaging Centre, Imaging Sciences Department, MRC Clinical Sciences Centre and [4 ]Department of Clinical Neurosciences, Imperial College London and GSK Clinical Imaging Centre, Hammersmith Hospital; and [5 ]Sobell Department of Movement Neuroscience and Movement Disorders and [6 ]Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College, London, United Kingdom

Author notes

Address for reprint requests and other correspondence: C. J. Stagg, FMRIB Centre, Department of Clinical Neurology, John Radcliffe Hospital, Oxford, OX3 9DU, UK (E-mail: cstagg@ 123456fmrib.ox.ac.uk )

Article

Publisher ID: J91060-8

DOI: 10.1152/jn.91060.2008

PMC ID: 2694115

PubMed ID: 19339458

SO-VID: 1946ad1d-1d6a-4cab-9de8-a79272e4439d

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This document may be redistributed and reused, subject to www.the-aps.org/publications/journals/funding_addendum_policy.htm.

Neurochemical Effects of Theta Burst Stimulation as Assessed by Magnetic Resonance Spectroscopy

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Abstract

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Karger: Neurology and Neuroscience

Most cited references 43

Simultaneous in vivo spectral editing and water suppression.

Localization of the motor hand area to a knob on the precentral gyrus. A new landmark.

Responses to rapid-rate transcranial magnetic stimulation of the human motor cortex.

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