Article

Noninvasive brain stimulation: From physiology to network dynamics and back

1] Human Cortical Physiology and Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke, US National Institutes of Health, Bethesda, Maryland, USA. [2].
Nature Neuroscience (Impact Factor: 14.98). 06/2013; 16(7):838-844. DOI: 10.1038/nn.3422
Source: PubMed

ABSTRACT Noninvasive brain stimulation techniques have been widely used for studying the physiology of the CNS, identifying the functional role of specific brain structures and, more recently, exploring large-scale network dynamics. Here we review key findings that contribute to our understanding of the mechanisms underlying the physiological and behavioral effects of these techniques. We highlight recent innovations using noninvasive stimulation to investigate global brain network dynamics and organization. New combinations of these techniques, in conjunction with neuroimaging, will further advance the utility of their application.

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Available from: Marco Sandrini, Aug 14, 2015
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    • "The aim of the present research was to collect new evidence on the neural bases of SoA by introducing novel aspects compared to the abovementioned studies. (i) Transcranial direct current stimulation (tDCS: Dayan et al., 2013) was adopted, for the first time in this research field, for its potential use in the clinical practice. "
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    ABSTRACT: Intentional Binding (IB) refers to the temporal compression between a voluntary action and its sensory effect, and it is considered an implicit measure of sense of agency (SoA), that is, the capacity of controlling one's own actions. IB has been thoroughly studied from a behavioural point of view, but only few studies have investigated its neural underpinnings, always using the same two paradigms. Although providing evidence that the supplementary motor complex is involved, findings are still too scarce to draw definitive conclusions. The aim of the present study was to establish a causal relationship between the pre-supplementary motor area (pre-SMA) - known for its key role in action planning and initiation - and IB by means of transcranial direct current stimulation (tDCS). Participants underwent anodal, cathodal, and sham control stimulations during three separate sessions (Experimenti I). Subsequently, they underwent the same stimulation protocol (Experiment II) using as control a region potentially involved in the processing of the sensory effects of voluntary action (i.e., the right primary auditory cortex for the auditory effects of action). A significant reduction of IB was found only after stimulation of the pre-SMA, which supports the causal contribution of this prefrontal area in the perceived linkage between action and its effects. Since SoA could be disrupted in many psychiatric and neurological diseases, these results have direct clinical relevance as tDCS could be successfully used in this domain in virtue of the promising advantages it offers for rehabilitation. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    European Journal of Neuroscience 05/2015; DOI:10.1111/ejn.12937 · 3.67 Impact Factor
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    • "Intermittent theta burst stimulation (iTBS), a variant of repetitive transcranial magnetic stimulation (TMS), can non-invasively induce increases in excitability of the underlying cortex [7]. Increased excitability is mediated through long-term potentiation (LTP) like mechanisms [5]. "
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    ABSTRACT: Differences in cortical control across the different muscles of the upper limb may mitigate the efficacy of TMS interventions targeting a specific muscle. The current study sought to determine whether weak concurrent contraction during TMS could enhance the efficacy of intermittent theta burst stimulation (iTBS) in the forearm flexors. Motor evoked potentials (MEP) were elicited from the flexor (FCR) and extensor carpi radialis (ECR) motor cortical hotspots before and after iTBS over the FCR cortical hotspot. During iTBS the FCR was either relaxed (iTBS-Relax) or tonically contracted to 10% of maximum voluntary force (iTBS-Contract). iTBS-Relax failed to produce consistent potentiation of MEPFCR amplitude. Individuals with a relatively lower RMTFCR compared RMTECR demonstrated MEPFCR facilitation post-iTBS-Relax. Individuals with relatively higher RMTFCR demonstrated less facilitation and even suppression of MEPFCR amplitude. iTBS-Contract facilitated MEPFCR amplitude but only for MEPFCR evoked from the ECR hotspot. Interactions between overlapping cortical representations determine the efficacy of iTBS. Tonic contraction increases the efficacy of iTBS by enhancing the volume of the cortical representation. However, metaplastic effects may attenuate the enhancement of MEP gain at the motor cortical hotspot. The use of TMS as an adjunct to physical therapy should account for inter-muscle interactions when targeting muscles of the forearm. Copyright © 2015. Published by Elsevier Ireland Ltd.
    Neuroscience Letters 02/2015; 591. DOI:10.1016/j.neulet.2015.02.020 · 2.06 Impact Factor
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    • "While it was shown that the application of electric currents to the brain can modulate mood, cognition and behavior, only the recent development of neurophysiological and neuroimaging tools allows systematic investigation of the mechanisms underlying these effects (Bolwig, 2014). Besides invasive stimulation techniques, such as deep brain stimulation or motor cortex stimulation, non-invasive forms of brain stimulation (NIBS), including transcranial direct current stimulation (tDCS) or transcranial magnetic stimulation (TMS) are increasingly used (Liew et al., 2014) and their effects on brain physiology are being investigated (Dayan et al., 2013). For instance, it was shown that tDCS, i.e. the application of weak electric direct currents (DC) of 1–2 mA through saline soaked sponges or electrodes, can improve learning and consolidation throughout different domains (Reis et al., 2008; Marshall et al., 2004). "
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    ABSTRACT: Stroke is among the leading causes of long-term disabilities leaving an increasing number of people with cognitive, affective and motor impairments depending on assistance in their daily life. While function after stroke can significantly improve in the first weeks and months, further recovery is often slow or non-existent in the more severe cases encompassing 30-50% of all stroke victims. The neurobiological mechanisms underlying recovery in those patients are incompletely understood. However, recent studies demonstrated the brain's remarkable capacity for functional and structural plasticity and recovery even in severe chronic stroke. As all established rehabilitation strategies require some remaining motor function, there is currently no standardized and accepted treatment for patients with complete chronic muscle paralysis. The development of brain-machine interfaces (BMIs) that translate brain activity into control signals of computers or external devices provides two new strategies to overcome stroke-related motor paralysis. First, BMIs can establish continuous high-dimensional brain-control of robotic devices or functional electric stimulation (FES) to assist in daily life activities (assistive BMI). Second, BMIs could facilitate neuroplasticity, thus enhancing motor learning and motor recovery (rehabilitative BMI). Advances in sensor technology, development of non-invasive and implantable wireless BMI-systems and their combination with brain stimulation, along with evidence for BMI system's clinical efficacy suggest that BMI-related strategies will play an increasing role in neurorehabilitation of stroke. Copyright © 2014. Published by Elsevier Inc.
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