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.

Full-text

Available from: Marco Sandrini, Jun 13, 2015
1 Follower
 · 
152 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Corticobasal Syndrome (CBS) is a neurodegenerative disorder that overlaps both clinically and neuropathologically with Frontotemporal dementia (FTD) and is characterized by apraxia, alien limb phenomena, cortical sensory loss, cognitive impairment, behavioral changes and aphasia. It has been recently demonstrated that transcranial direct current stimulation (tDCS) improves naming in healthy subjects and in subjects with language deficits. The aim of the present study was to explore the extent to which anodal tDCS over the parietal cortex (PARC) could facilitate naming performance in CBS subjects. Anodal tDCS was applied to the left and right PARC during object and action naming in seventeen patients with a diagnosis of possible CBS. Participants underwent two sessions of anodal tDCS (left and right) and one session of placebo tDCS. Vocal responses were recorded and analyzed for accuracy and vocal Reaction Times (vRTs). A shortening of naming latency for actions was observed only after active anodal stimulation over the left PARC, as compared to placebo and right stimulations. No effects have been reported for accuracy. Our preliminary finding demonstrated that tDCS decreased vocal reaction time during action naming in a sample of patients with CBS. A possible explanation of our results is that anodal tDCS over the left PARC effects the brain network implicated in action observation and representation. Further studies, based on larger patient samples, should be conducted to investigate the usefulness of tDCS as an additional treatment of linguistic deficits in CBS patients.
    Frontiers in Aging Neuroscience 04/2015; 7. DOI:10.3389/fnagi.2015.00049 · 2.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Recently, multifocal transcranial current stimulation (tCS) devices using several relatively small electrodes have been used to achieve more focal stimulation of specific cortical targets. However, it is becoming increasingly recognized that many behavioral manifestations of neurological and psychiatric disease are not solely the result of abnormality in one isolated brain region but represent alterations in brain networks. In this paper we describe a method for optimizing the configuration of multifocal tCS for stimulation of brain networks, represented by spatially extended cortical targets. We show how, based on fMRI, PET, EEG or other data specifying a target map on the cortical surface for excitatory, inhibitory or neutral stimulation and a constraint of the maximal number of electrodes, a solution can be produced with the optimal currents and locations of the electrodes. The method described here relies on a fast calculation of multifocal tCS electric fields (including components normal and tangential to the cortical boundaries) using a five layer finite element model of a realistic head. Based on the hypothesis that the effects of current stimulation are to first order due to the interaction of electric fields with populations of elongated cortical neurons, it is argued that the optimization problem for tCS stimulation can be defined in terms of the component of the electric field normal to the cortical surface. Solutions are found using constrained least squares to optimize current intensities, while electrode number and their locations are selected using a genetic algorithm. For direct current tCS (tDCS) applications, we provide some examples of this technique using an available tCS system providing 8 small Ag/AgCl stimulation electrodes. We demonstrate the approach both for localized and spatially extended targets defined using rs-fcMRI and PET data, with clinical applications in stroke and depression. Finally, we extend these ideas to more general stimulation protocols, such as alternating current tCS (tACS).
    NeuroImage 12/2013; 89. DOI:10.1016/j.neuroimage.2013.12.002 · 6.13 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Over the last decade, electrophysiological studies in parkinsonian animals have shown that there are abnormalities of synaptic plasticity in motor areas of cortex and basal ganglia. In humans with Parkinson's disease (PD), cortical plasticity has been widely investigated using transcranial magnetic stimulation. A number of studies have reported abnormal responses to several different conditioning protocols, but their relationship to altered basal ganglia output and dopaminergic loss is still not entirely clear. Thus in the near future it seems unlikely that measures of cortical plasticity could be used as a biomarker of disease severity and progression. In this review we provide an overview on current knowledge of abnormalities of plasticity in PD in the light of recent advances in parkinsonian animal models. Finally we will discuss the relevance of abnormalities of plasticity in the clinical context of PD. Copyright © 2015. Published by Elsevier Ireland Ltd.
    Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 02/2015; DOI:10.1016/j.clinph.2015.02.009 · 2.98 Impact Factor