Working memory, as associated with ‘brain training’ and ‘plasticity‘, is often expressed as what one would wish to have more of, or at the very least, what one hopes not to lose as we age. (For a great overview of working memory and the how’s of enhancing it, see this fascinating post from neuroscientist Bradley Voytek’s blog Working memory and cognitive enhancement.)
Our aim was to determine whether anodal transcranial direct current stimulation, which enhances brain cortical excitability and activity, would modify performance in a sequential-letter working memory task when administered to the dorsolateral prefrontal cortex DLPFC. Fifteen subjects underwent a three-back working memory task based on letters. This task was performed during sham and anodal stimulation applied over the left DLPFC. Moreover seven of these subjects performed the same task, but with inverse polarity cathodal stimulation of the left DLPFC and anodal stimulation of the primary motor cortex M1. Our results indicate that only anodal stimulation of the left prefrontal cortex, but not cathodal stimulation of left DLPFC or anodal stimulation of M1, increases the accuracy of the task performance when compared to sham stimulation of the same area. This accuracy enhancement during active stimulation cannot be accounted for by slowed responses, as response times were not changed by stimulation. Our results indicate that left prefrontal anodal stimulation leads to an enhancement of working memory performance. Furthermore, this effect depends on the stimulation polarity and is specific to the site of stimulation. This result may be helpful to develop future interventions aiming at clinical benefits.
Cerebellum and processing of negative facial emotions: Cerebellar transcranial DC stimulation specifically enhances the emotional recognition of facial anger and sadness.
Some evidence suggests that the cerebellum participates in the complex network processing emotional facial expression. To evaluate the role of the cerebellum in recognising facial expressions we delivered transcranial direct current stimulation (tDCS) over the cerebellum and prefrontal cortex. A facial emotion recognition task was administered to 21 healthy subjects before and after cerebellar tDCS; we also tested subjects with a visual attention task and a visual analogue scale (VAS) for mood. Anodal and cathodal cerebellar tDCS both significantly enhanced sensory processing in response to negative facial expressions (anodal tDCS, p=.0021; cathodal tDCS, p=.018), but left positive emotion and neutral facial expressions unchanged (p>.05). tDCS over the right prefrontal cortex left facial expressions of both negative and positive emotion unchanged. These findings suggest that the cerebellum is specifically involved in processing facial expressions of negative emotion.
This is pretty fascinating. If I’m getting it, it implies that for this particular brain function there is an upward bounded capability. If you’re already there (say, genius level) tDCS won’t improve your performance, but it will if you’re not already wired at the upper bound! I know from my CambridgeBrainScience.com tests, that I’m especially weak in the VSTM (visual short-term memory) area. [Unfortunately there’s a paywall around this and most other journal paper.] Paper originates from the Institute of Cognitive Neuroscience at the National Central University, Taiwan.
Here we show that artificially elevating parietal activity via positively charged electric current through the skull can rapidly and effortlessly improve people’s VSTM performance.
…The high performers, however, did not benefit from tDCS as they showed equally large waveforms in N2pc and CDA, or SPCN (sustained parietal contralateral negativity), before and after the stimulation such that electrical stimulation could not help any further, which also accurately accounts for our behavioral observations. Together, these results suggest that there is indeed a fixed upper limit in VSTM, but the low performers can benefit from neurostimulation to reach that maximum via enhanced comparison processes, and such behavioral improvement can be directly quantified and visualized by the magnitude of its associated electrophysiological waveforms.
Reversing (usual) placement of electrodes in a treatment-resistant major depression (TRD) study resulted in no apparent effect.
Side effects did not differ between the two groups and in general the treatment was very well tolerated.
Conclusion: Anodal stimulation to the left DLPFC and cathodal stimulation to the right DLPFC was not efficacious in TRD. However, a number of methodological limitations warrant caution in generalizing from this study.
The Children’s Hemiplegia and Stroke Association CHASA is assisting researchers in the Physical Therapy Department at the University of Minnesota with recruitment of participants for a non-invasive brain stimulation research study. The purpose of this study is to investigate the use of a form of non-invasive brain stimulation, transcranial Direct Current Stimulation tDCS, for interventions in rehabilitation for children who have hemiparesis weakness on one side of the body. This type of non-invasive brain stimulation has shown beneficial behavioral effects and is more cost-effective and portable than previous types. Being able to combine tDCS with other therapies could improve hand function in children with hemiparesis more effectively than each therapy separately.
There seems to be a LOT of activity going on in the medical profession around tDCS. You can monitor ClinicalTrials.gov to keep an eye on new and recruiting tdcs studies. If you start here and modify your search with your location, you may find a study in your area.
At around minute 13, Tali Sharot describes how she and collaborator Dr Ryota Kanai were able to influence the outcome of experiments designed to test optimism bias by applying TMS (transcranial magnetic stimulation). Amazing!
One way to think about this (very generally) is that, in this case, TMS had both a positive and negative impact. This should also serve as cautionary to anyone self-experimenting with tDCS.
I recently reached out to Dr. Mark Beeman of Northwestern around the subject of testing the efficacy of tDCS especially in the context of DIY. I became aware of Dr. Beeman’s work through the new Jonah Lehrer book, ‘Imagine’. (I haven’t read it actually, but have listened to Lehrer discuss the book at length in numerous podcasts.) Dr. Beeman took the time to respond to my email stating that he was in fact at work on some experiments that use tDCS. About self-experiments, he had this to say…
I’d be hesitant to do too much self-experimentation. Not that I worry about causing direct damage, but brain activity is often a delicate balance, and enhancing some process may have adverse effects on another.
I also heard back from the Laboratory of Cognition and Neural Stimulation at the University of Pennsylvania. They are who posted the questionnaire. Basically it was just a follow-up email asking more questions. I have yet to correspond with anyone personally and they have so far signed their emails as Research Specialist.
The main experiment consisted of a two-minute baseline period of walking with both belts at the same slow speed, followed by a 15-minute period with the belts at two separate speeds. While people were on the treadmill, researchers stimulated one side of the cerebellum to assess the impact on the rate of re-adjustment to a symmetric walking pattern.
Dr. Bastian’s team found not only that cerebellar tDCS can change the rate of cerebellum-dependent locomotor learning, but specifically that the anode speeds up learning and the cathode slows it down. It was also surprising that the side of the cerebellum that was stimulated mattered; only stimulation of the side that controls the leg walking on the faster treadmill belt changed adaptation rate.
“It is important to demonstrate that we can make learning faster or slower, as it suggests that we are not merely interfering with brain function,” says Dr. Bastian. “Our findings also suggest that tDCS can be selectively used to assess and understand motor learning.”
Major depressive disorder (MDD) is a common psychiatric illness, with 6-12% lifetime prevalence. It is also among the five most disabling diseases worldwide. Current pharmacological treatments, although relatively effective, present important side effects that lead to treatment discontinuation. Therefore, novel treatment options for MDD are needed. Here, we discuss the recent advancements of one new neuromodulatory technique – transcranial direct current stimulation (tDCS) – that has undergone intensive research over the past decade with promising results. tDCS is based on the application of weak, direct electric current over the scalp, leading to cortical hypo- or hyper-polarization according to the specified parameters. Recent studies have shown that tDCS is able to induce potent changes in cortical excitability as well as to elicit long-lasting changes in brain activity. Moreover, tDCS is a technique with a low rate of reported side effects, relatively easy to apply and less expensive than other neuromodulatory techniques – appealing characteristics for clinical use. In the past years, 4 of 6 phase II clinical trials and one recent meta-analysis have shown positive results in ameliorating depression symptoms. tDCS has some interesting, unique aspects such as noninvasiveness and low rate of adverse effects, being a putative substitutive/augmentative agent for antidepressant drugs, and low-cost and portability, making it suitable for use in clinical practice. Still, further phase II and phase III trials are needed as to better clarify tDCS role in the therapeutic arsenal of MDD.
Fig. 2. Montage of transcranial direct current stimulation.The figures show the main montages used for major depression: in both, the anode is positioned over the left dorsolateral prefrontal cortex. The cathode can be either placed over the right dorsolateral prefrontal cortex (Figure A) or the right supraorbital area (Figure B).
Depression scores significantly decreased p<.0005 after the treatment. No serious adverse events occurred. Several transient minor AEs and occasional changes of blood pressure and heart rate were noted. Mini-mental status scores remained unchanged or increased after the treatment. All subjects were highly satisfied with the protocol and treatment results and described the desire to find new treatments for HIV-MDD as motivating participation. Conclusions: F indings support feasibility and clinical potential of tDCS for HIV-MDD patients, and justify larger-sample, sham-controlled trials.
Method—Twelve well-recovered chronic patients with subcortical stroke attended 2 training sessions during which either cathodal tDCS or a sham intervention were applied to the contralesional motor cortex in a double-blind, crossover design. Two different motor sequences, matched for their degree of complexity, were tested in a counterbalanced order during as well as 90 minutes and 24 hours after the intervention. Potential underlying mechanisms were evaluated with transcranial magnetic stimulation.
Results—tDCS facilitated the acquisition of a new motor skill compared with sham stimulation (P=0.04) yielding better task retention results. A significant correlation was observed between the tDCS-induced improvement during training and the tDCS-induced changes of intracortical inhibition (R2=0.63).
Conclusions—These results indicate that tDCS is a promising tool to improve not only motor behavior, but also procedural learning. They further underline the potential of noninvasive brain stimulation as an adjuvant treatment for long-term recovery, at least in patients with mild functional impairment after stroke.
Neuropathic pain NP is common in spinal cord injury SCI patients. One of its manifestations is a lowering of pain perception threshold in quantitative thermal testing QTT in dermatomes rostral to the injury level. Transcranial direct current stimulation tDCS combined with visual illusion VI improves pain in SCI patients. We studied whether pain relief with tDCS + VI intervention is accompanied by a change in contact heat- evoked potentials CHEPs or in QTT.
We examined 18 patients with SCI and NP before and after 2 weeks of daily tDCS + VI intervention. Twenty SCI patients without NP and 14 healthy subjects served as controls. We assessed NP intensity using a numerical rating scale NRS and determined heat and pain thresholds with thermal probes. CHEPs were recorded to stimuli applied at C4 level, and subjects rated their perception of evoked pain using NRS during CHEPs.
Thirteen patients reported a mean decrease of 50% in the NRS for NP after tDCS + VI. Evoked pain perception was significantly higher than in the other two groups, and reduced significantly together with CHEPs amplitude after tDCS + VI with respect to baseline. Pain perception threshold was significantly lower than in the other two groups before tDCS + VI intervention, and increased significantly afterwards.
Two weeks of tDCS + VI induced significant changes in CHEPs, evoked pain and heat pain threshold in SCI patients with NP. These neurophysiological tests might be objective biomarkers of treatment effects for NP in patients with SCI.
Results: Auditory verbal hallucinations were robustly reduced by tDCS relative to sham stimulation, with a mean diminution of 31% SD=14; d=1.58, 95% CI=0.76–2.40. The beneficial effect on hallucinations lasted for up to 3 months. The authors also observed an amelioration with tDCS of other symptoms as measured by the Positive and Negative Syndrome Scale d=0.98, 95% CI=0.22–1.73, especially for the negative and positive dimensions. No effect was observed on the dimensions of disorganization or grandiosity/excitement.
Conclusions: Although this study is limited by the small sample size, the results show promise for treating refractory auditory verbal hallucinations and other selected manifestations of schizophrenia.
Punchdrunk in Berlin? tDCS study recruiting participants.
Concussed athlethes have discrete decreased abilities in motor learning. Recent research could further show, that cortical plasticity, as measured by transcranial magnetic stimulation TMS is reduced. This is possibly due to an increased GABAergic activity, what have been found in concussed athletes by paired pulse protocols in TMS.GABAergic acitivty can be modulated by transcranial direct current stimulation tDCS in a polar-specific manner: anodal tDCS was able to decrease GABA, whereas cathodal tDCS increased tDCS.Our study aimes to assess the influence of anodal tDCS on cortical plsticity in concussed athlethes. We hypothesize, that anodal tDCS is able to increase cortical plsticity in concussed athlethes.