TDCS guided using fMRI significantly accelerates learning to identify concealed objects

Mind Research Network, Albuquerque, NM 87106, USA.
NeuroImage (Impact Factor: 6.36). 11/2010; 59(1):117-28. DOI: 10.1016/j.neuroimage.2010.11.036
Source: PubMed


The accurate identification of obscured and concealed objects in complex environments was an important skill required for survival during human evolution, and is required today for many forms of expertise. Here we used transcranial direct current stimulation (tDCS) guided using neuroimaging to increase learning rate in a novel, minimally guided discovery-learning paradigm. Ninety-six subjects identified threat-related objects concealed in naturalistic virtual surroundings used in real-world training. A variety of brain networks were found using functional magnetic resonance imaging (fMRI) data collected at different stages of learning, with two of these networks focused in right inferior frontal and right parietal cortex. Anodal 2.0 mA tDCS performed for 30 min over these regions in a series of single-blind, randomized studies resulted in significant improvements in learning and performance compared with 0.1 mA tDCS. This difference in performance increased to a factor of two after a one-hour delay. A dose-response effect of current strength on learning was also found. Taken together, these brain imaging and stimulation studies suggest that right frontal and parietal cortex are involved in learning to identify concealed objects in naturalistic surroundings. Furthermore, they suggest that the application of anodal tDCS over these regions can greatly increase learning, resulting in one of the largest effects on learning yet reported. The methods developed here may be useful to decrease the time required to attain expertise in a variety of settings.

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Available from: Vincent P Clark
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    • "These neuromodulatory effects are considered to underlie tDCS related improvements in learning and memory obtained across various stimulus modalities, including motor (Antal et al., 2004; Nitsche et al., 2003; Reis et al., 2009), visual (Chi et al., 2010; Clark et al., 2012), and verbal (De Vries et al., 2010; Elmer et al., 2009; Flöel et al., 2008; Javadi and Walsh, 2012). These promising findings have helped to establish tDCS as a new technique to modulate and enhance brain functioning , with potential treatment applications in rehabilitation for brain illness or injury (Baker et al., 2010; Monti et al., 2008) and enhancing education and training (Clark et al., 2012; Martin et al., 2013). Previous studies using tDCS to enhance verbal memory have varied in their approach, primarily through focussing on different sites of stimulation (i.e., LDLPFC: Elmer et al., 2009; Javadi et al., 2012; Javadi and Walsh, 2012; Marshall et al., 2004; PT: Fiori et al., 2011; Flöel et al., 2008; Jones et al., 2014; motor cortex: Liuzzi et al., 2010). "
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    ABSTRACT: Declarative verbal learning and memory is known to be lateralised to the dominant hemisphere and to be subserved by a network of structures, including those located in frontal and temporal regions. These structures support critical components of verbal memory, including working memory, encoding, and retrieval. Their relative functional importance in facilitating declarative verbal learning and memory, however, remains unclear. To investigate the different functional roles of these structures in subserving declarative verbal learning and memory performance by applying a more focal form of transcranial direct current stimulation, "High Definition tDCS" (HD-tDCS). Additionally, we sought to examine HD-tDCS effects and electrical field intensity distributions using computer modelling. HD-tDCS was administered to the left dorsolateral prefrontal cortex (LDLPFC), planum temporale (PT), and left medial temporal lobe (LMTL) to stimulate the hippocampus, during learning on a declarative verbal memory task. Sixteen healthy participants completed a single blind, intra-individual cross-over, sham-controlled study which used a Latin Square experimental design. Cognitive effects on working memory and sustained attention were additionally examined. HD-tDCS to the LDLPFC significantly improved the rate of verbal learning (p=0.03, η(2)= 0.29) and speed of responding during working memory performance (p=0.02, η(2)= 0.35), but not accuracy (p=0.12, η(2)= 0.16). No effect of tDCS on verbal learning, retention, or retrieval was found for stimulation targeted to the LMTL or the PT. Secondary analyses revealed that LMTL stimulation resulted in increased recency (p=0.02, η(2)= 0.31) and reduced mid-list learning effects (p=0.01, η(2)= 0.39), suggesting an inhibitory effect on learning. HD-tDCS to the LDLPFC facilitates the rate of verbal learning and improved efficiency of working memory may underlie performance effects. This focal method of administrating tDCS has potential for probing and enhancing cognitive functioning. Copyright © 2015. Published by Elsevier Inc.
    Full-text · Article · May 2015 · NeuroImage
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    • "etal.(2014)).Hereweprovideafewexamplesoftheeffectsof tDCSonmorecomplextasksrepresentativeofworksettings. Oneexampleinvolvessurveillanceandsecurityoperations,as inthreatdetection(ParasuramanandGalster,2013).Accurate andtimelydetectionofobscuredorconcealedobjects,orthe actionsandmovementsofotherpeople,isacriticalneedinmany suchworkenvironments,bothinthemilitaryandincivilian organizations.Skillinsuchthreatdetectiontaskstypically developsonlyafterextensivetraininglastingmanydays.Can thedevelopmentofexpertisebespeededupwithtDCS?Recent studiesprovideapositiveanswer(Clarketal.,2012;Falconeetal., 2012).Thesestudiesinvolveduseofacomplextaskrequiring participantstowatchvideosofnaturalisticscenescontaining movementsofsoldiersandcivilians.Stillimageswereextracted fromthevideosandmanipulatedsothathalfweretargets, definedasconcealedobjects(e.g.,bombs),peopleengagingin threateningactivity(e.g.,snipers),andsoon,whereasthesame scenewithoutthethreatwasanon-target.AnfMRIstudywas firstconductedtodetermineoptimalsitesforapplicationoftDCS (Clarketal.,2012).Atotalof104participantsvolunteeredfor thestudyandwereimagedasnovices.Asubset,13participants performedthetaskduringfMRIdatacollectiontoidentifythe brainnetworkssupportingtheidentificationofconcealedobjects andchangeswithlearning.Theresultsindicatedthattheright inferiorfrontalgyruswasthemajorlocusofadistributedbrain networkthatmediatedacquisitionofthethreatdetectiontask andsowaschosenastheoptimalstimulationsite. Falconeetal.(2012)examinedwhethertDCSappliedto "
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    ABSTRACT: Contemporary studies with transcranial direct current stimulation (tDCS) provide a growing base of evidence for enhancing cognition through the non-invasive delivery of weak electric currents to the brain. The main effect of tDCS is to modulate cortical excitability depending on the polarity of the applied current. However, the underlying mechanism of neuromodulation is not well understood. A new generation of functional near infrared spectroscopy (fNIRS) systems is described that are miniaturized, portable, and include wearable sensors. These developments provide an opportunity to couple fNIRS with tDCS, consistent with a neuroergonomics approach for joint neuroimaging and neurostimulation investigations of cognition in complex tasks and in naturalistic conditions. The effects of tDCS on complex task performance and the use of fNIRS for monitoring cognitive workload during task performance are described. Also explained is how fNIRS + tDCS can be used simultaneously for assessing spatial working memory. Mobile optical brain imaging is a promising neuroimaging tool that has the potential to complement tDCS for realistic applications in natural settings.
    Full-text · Article · Mar 2015 · Frontiers in Systems Neuroscience
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    • "Previous studies have demonstrated the safety of 2 mA stimulation on a range of tasks (Keeser et al., 2011; Chib et al., 2013; Clark and Parasuraman, 2014), including complex, real-world tasks (Fecteau et al., 2007; Clark et al., 2012; Falcone et al., 2012). Furthermore, studies comparing dosage levels have demonstrated performance modulation with 2 mA, but not with 1 mA (Boggio et al., 2006; Teo et al., 2011; Moos et al., 2012) or 0.6 mA (Clark et al., 2012) compared to sham. Participants were blinded as to whether they were administered active or sham stimulation. "
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    ABSTRACT: There is a need to facilitate acquisition of real world cognitive multi-tasks that require long periods of training (e.g., air traffic control, intelligence analysis, medicine). Non-invasive brain stimulation-specifically transcranial Direct Current Stimulation (tDCS)-has promise as a method to speed multi-task training. We hypothesized that during acquisition of the complex multi-task Space Fortress, subtasks that require focused attention on ship control would benefit from tDCS aimed at the dorsal attention network while subtasks that require redirection of attention would benefit from tDCS aimed at the right hemisphere ventral attention network. We compared effects of 30 min prefrontal and parietal stimulation to right and left hemispheres on subtask performance during the first 45 min of training. The strongest effects both overall and for ship flying (control and velocity subtasks) were seen with a right parietal (C4, reference to left shoulder) montage, shown by modeling to induce an electric field that includes nodes in both dorsal and ventral attention networks. This is consistent with the re-orienting hypothesis that the ventral attention network is activated along with the dorsal attention network if a new, task-relevant event occurs while visuospatial attention is focused (Corbetta et al., 2008). No effects were seen with anodes over sites that stimulated only dorsal (C3) or only ventral (F10) attention networks. The speed subtask (update memory for symbols) benefited from an F9 anode over left prefrontal cortex. These results argue for development of tDCS as a training aid in real world settings where multi-tasking is critical.
    Full-text · Article · Sep 2014 · Frontiers in Human Neuroscience
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