Biophysical foundation underlying TMS: Setting the stage for an effective use of neurostimulation in the cognitive neurosciences

Highland Instruments, Cambridge, MA 02138, USA.
Cortex (Impact Factor: 5.13). 11/2008; 45(9):1025-34. DOI: 10.1016/j.cortex.2008.10.002
Source: PubMed


Transcranial Magnetic Stimulation (TMS) induces electrical currents in the brain to stimulate neural tissue. This article reviews our present understanding of TMS methodology, focusing on its biophysical foundations. We concentrate on how the laws of electromagnetic induction apply to TMS; addressing issues such as the location, area (i.e., focality), depth, and mechanism of TMS. We also present a review of the present limitations and future potential of the technique.

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    • "Neuromodulatory brain stimulation can induce plastic reorganization of cortical circuits which persist beyond the period of stimulation [1]. A variety of neuromodulation techniques are currently used to modulate brain activity, the most common of which are repetitive Transcranial Magnetic Stimulation (rTMS) and transcranial Direct Current Stimulation (tDCS). "
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    ABSTRACT: Neuromodulatory brain stimulation can induce plastic reorganization of cortical circuits that persist beyond the period of stimulation. Most of our current knowledge about the physiological properties has been derived from the motor cortex. The integration of transcranial magnetic stimulation (TMS) and electroencephalography (EEG) is a valuable method for directly probing excitability, connectivity and oscillatory dynamics of regions throughout the brain. Offering in depth measurement of cortical reactivity, TMS-EEG allows the evaluation of TMS-evoked components that may act as a marker for cortical excitation and inhibition. A growing body of research is using concurrent TMS and EEG (TMS-EEG) to explore the effects of different neuromodulatory techniques such as repetitive TMS and transcranial direct current stimulation on cortical function, particularly in non-motor regions. In this review, we outline studies examining TMS-evoked potentials and oscillations before and after, or during a single session of brain stimulation. Investigating these studies will aid in our understanding of mechanisms involved in the modulation of excitability and inhibition by neuroplasticity following different stimulation paradigms. Copyright © 2015 Elsevier Inc. All rights reserved.
    Brain Stimulation 07/2015; 8(6). DOI:10.1016/j.brs.2015.07.029 · 4.40 Impact Factor
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    • "Coils are placed on the surface of the skull and produce rapidly changing , strong electromagnetic fields, which noninvasively induce currents in neural populations that interfere with normal neural functioning. The precise mechanisms of TMS action are still incompletely understood (Valero-Cabré et al., 2007; Wagner et al., 2009). While often labeled as 'virtual lesions', the impact of TMS is neither virtual nor does it result in actual lesions. "
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    ABSTRACT: The article reviews studies that have used the perturbation approach of Transcranial Magnetic Stimulation (TMS) to assess the control of attention and manual response selection in conflict situations as elicited in three established paradigms: the Simon paradigm, the Flanker paradigm, and the Stroop paradigm. After describing the experimental conflict paradigms and briefly introducing TMS we review evidence for the involvement of different frontal and parietal cortical regions in the control of attention and response selection. For example, areas such as the frontal eye field (FEF) appear to significantly contribute to the encoding of spatial attributes of stimuli and areas of the parietal cortex, such as angular gyrus (AG), mediate the allocation of spatial attention and orienting. The dorsal medial frontal cortex (dMFC), supramarginal gyrus (SMG) and pre-supplementary motor area (pre-SMA) appear to be more related to response-related aspects of the conflicts (i.e., enhancement of signals related to correct movements, transformation of spatial information action codes, resolution of response selection conflicts, respectively). The reviewed studies illustrate crucial benefits but also limitations of TMS as well as the value of the combination of TMS with other methods. We suggest topics and approaches for future studies. Copyright © 2015. Published by Elsevier Ltd.
    Neuropsychologia 02/2015; 74. DOI:10.1016/j.neuropsychologia.2015.02.008 · 3.30 Impact Factor
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    • "Transcranial magnetic stimulation (TMS) is a noninvasive brain stimulation technique that uses the principles of electromagnetic induction to induce an electric current within the surface of the human cortex. This current may be of sufficient intensity to depolarize neurons in a certain area (Wagner et al., 2009). Single-pulse and paired-pulse TMS paradigms can be used in the evaluation of cortical excitability with measurements of short interval cortical inhibition (SICI), intracortical facilitation (ICF), and long interval cortical inhibition (LICI) (Kujirai et al., 1993). "
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    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; 242. DOI:10.1016/j.jneumeth.2014.12.018 · 2.05 Impact Factor
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