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Can learning be facilitated by transcranial magnetic stimulation?

Can learning be facilitated by transcranial magnetic stimulation?


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I read a book a while ago called The Brain that Changes Itself by Norman Doidge (2007), and it brought to my attention a machine known as a transcranial magnetic stimulator (TMS) which can noninvasively excite neurons in someone's brain. Doidge mentioned an experiment that used TMS to excite the neurons in patients' pleasure centers, which caused them so much enjoyment that some actually begged the researchers to do it again.

I have also learned about PTSD (posttraumatic stress disorder) and how it happens when overly excited neurons are firing, creating a strong memory.

What if the TMS was made to excite the part of the brain that stores memory (the amygdala I believe) in a fashion similar to PTSD's inadvertently created states, and during the hyper-excited state, the subject was given accurate information to memorize? I specify "accurate" because whatever would be learned or observed in this state would be powerfully etched into memory.

I am not a neuroscientist, so please give answers in layman's terms.

I would like to know if it is possible, what the mechanism would be that would allow us to experience improved learning and what the possible side effects would be.

Reference

Doidge, N. (2007). The brain that changes itself: Stories of personal triumph from the frontiers of brain science. Official website: http://www.normandoidge.com/normandoidge.com/MAIN.html.


Sadly (or should I be happy that Google is this awesome? Not to mention the rate of scientific progress!), all I really had to do to come up with an answer was perform a Google search for "learning transcranial magnetic stimulation". The first hit, a ScienceDaily page (Ruhr-University Bochum, 2011) page, lists some journal references (Mix, Benali, Eysel, & Funke, 2010; Benali et al., 2011) that effectively say (in laymen's terms), "Yes!" Here's ScienceDaily's summary (I'll let you read the rest at the source):

What sounds like science fiction is actually possible: thanks to magnetic stimulation, the activity of certain brain nerve cells can be deliberately influenced. What happens in the brain in this context has been unclear up to now. Medical experts have now shown that various stimulus patterns changed the activity of distinct neuronal cell types. In addition, certain stimulus patterns led to rats learning more easily. [Emphasis added.]

To show how hard I'm working to really earn that bounty of yours, here's the summary from the second Google hit, a review article on this very topic (Reis et al., 2008; again, plenty more info at the source):

In summary, the scarce studies performed so far point to the encouraging conclusion that noninvasive brain stimulation can contribute to the understanding of mechanisms underlying motor learning and motor memory formation and raise the exciting hypothesis that this increased understanding could in the future result in the development of new strategies to enhance specific stages of learning and memory processing in healthy humans and in patients with brain lesions (see chapter by Gerloff et al.). [Gerloff et al. doesn't appear in the references; emphasis added.]


Edit: I see from your comment that you want me to explain the mechanism. Since you offer a bounty, I'll play along and dance for it a bit. Here's another excerpt from Reis and colleagues (2008, page 6 of 16):

It would be theoretically possible to facilitate motor learning processes in which [the primary motor cortex] is involved by enhancing excitability in the “learning” [primary motor cortex (Pascual-Leone, Valls-Solé, Wassermann, & Hallett, 1994)] or by decreasing excitability in the “resting” [primary motor cortex (Schambra, Sawaki, & Cohen, 2003; Plewnia, Lotze, & Gerloff, 2003)], but see also Wassermann[, Wedegaertner, Ziemann, George, & Chen (1998)]. The intrinsic intracortical mechanisms by which these oversimplified models may operate remain to be identified ([Perez & Cohen, 2008; Daskalakis, Paradiso, Christensen, Fitzgerald, Gunraj, & Chen, 2004; Koch, Franca, Mochizuki, Marconi, Caltagirone, & Rothwell, 2007;] see for discussion chapters by Walsh et al., Di Lazzaro et al., Berardelli et al.). [References unavailable for these three discussion chapters; emphasis added.]

You may want to read the review further for yourself or ask follow-up questions if this is an unsatisfactory explanation of the mechanism.


Since that review was a little hesitant to conclude conclusively, and it's five years old now, I'll also throw in a brand-new bit of original research (Wall et al., 2013) that demonstrates the supportive trend continues:

Conclusion: These preliminary findings suggest rTMS does not adversely impact neurocognitive functioning in adolescents and may provide subtle enhancement of verbal memory as measured by the CAVLT. Further controlled investigations with larger sample sizes and rigorous trial designs are warranted to confirm and extend these findings. [Emphasis added.]

$uparrow$ That $uparrow$ was the fifth Google hit! Also, the seventh (Jelić et al., 2013) says it's not a placebo effect!

Going a little wide, transcranial direct current stimulation (which is somewhat different from magnetic stimulation, though maybe not in ways that concern you) works too (Fields, 2011; Kincses, Antal, Nitsche, Bártfai, & Paulus, 2004; Fregni et al., 2005; Nitsche et al., 2003; Ohn et al., 2008; Flöel, Rösser, Michka, Knecht, & Breitenstein, 2008; Chi & Snyder, 2012)-you can even try it yourself for $249 or £179! I just had to follow a few links from the 14th Google hit (Mims, 2012) to find all that. I'm a little shocked (pardon the pun) at how legit this actually seems…

Edit (by Fizz): Note that a more recent (2017) meta-analysis of tDCS studies found significant problems with their p-curves, making the authors of this meta-analysis conclude that

Using a p-curve analysis, we found no evidence that the tDCS studies had evidential value (33% power or greater), with the estimate of statistical power of these studies being approximately 14% for the cognitive studies, and 5% (what would be expected from randomly generated data) for the working memory studies.

Also (16th Google hit), it looks like the U.S. National Institutes of Health Clinical Center is currently recruiting participants for their study, "The Effect of Transcranial Magnetic Stimulation on Learning With Reward in Healthy Humans", so maybe you could even get Uncle Sam to pay you (for testing magnetic, not electrical stimulation)! However, if I'm reading that right, it's a study of learning disruption, which is another potential (and maybe not-so-desirable) application of TMS, according to the 18th hit (De Weerd et al., 2012).


Edit: Reis and colleagues (2008) also review this disruptive process somewhat; I get the impression that disruption is much easier than enhancement to achieve with magnetic stimulation (not sure whether this applies to direct electrical current as well). It seems TMS has been used mostly to knock out brain function temporarily in localized areas to simulate the effects of brain lesions. Use of TMS to enhance excitability rather than inhibit it seems to be the more recent innovation, and maybe a separable effect (i.e., it may be possible to excite the brain using TMS without causing inhibition).


In anticipation of the next question, "Is it safe?" I feel I should add that this is definitely not my area of expertise - I got a B- in biopsych as an undergrad - so again, I'll let the experts speak for themselves (Poreisz, Boros, Antal, & Paulus, 2007), but as a fan of dystopian sci-fi, I will at least say that the short-term dangers seem like they could've been much worse! Same for the ethical ramifications, more or less (Hamilton, Messing, & Chatterjee, 2011). It's reassuring to see so much thought going into this already; I might otherwise be worried about how far behind the times we seem to be here! BTW, these last revelations come thanks in part to the 33rd Google hit (Oremus, 2013). I'm afraid no amount of tDCS will allow us to keep up with Google…

P.S. From what I've seen in skimming some of these, it doesn't have anything in particular to do with the limbic system (which includes the amygdala). I saw a brief explanation suggesting it affects myelination, which is basically the process by which the brain speeds up electrical signal transmission. Myelin is a sort of segmented coating for the axons of neurons, which can be quite long individually. Myelin allows electrical signals (action potentials) to jump across myelinated segments quickly, rather than propagating relatively slowly across every millimeter in the normal fashion. I also saw some indication that transcranial electromagnetic (didn't note which) stimulation might speed up other aspects of neural construction, such as the rate at which connections form (not just the rate at which they upgrade from the neural equivalents of a dial-up modem to fiber-optic).

References

Benali, A., Trippe, J., Weiler, E., Mix, A., Petrasch-Parwez, E., Girzalsky, W.,… & Funke, K. (2011). Theta-burst transcranial magnetic stimulation alters cortical inhibition. The Journal of Neuroscience, 31(4), 1193-1203.
Boggio, P. S., Ferrucci, R., Rigonatti, S. P., Covre, P., Nitsche, M., Pascual-Leone, A., & Fregni, F. (2006). Effects of transcranial direct current stimulation on working memory in patients with Parkinson's disease. Journal of the Neurological Sciences, 249(1), 31-38. Retrieved from http://www.tmslab.org/publications/154.pdf.
Chi, R. P., & Snyder, A. W. (2012). Brain stimulation enables the solution of an inherently difficult problem. Neuroscience Letters, 515(2), 121-124. Retrieved from http://ingienous.com/wp-content/uploads/2012/05/snyder-9-dots-paper.pdf.
Daskalakis, Z. J., Paradiso, G. O., Christensen, B. K., Fitzgerald, Gunraj, & Chen. (2004). Exploring the connectivity between the cerebellum and motor cortex in humans. Journal of Physiology, 557, 689-700. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1665103/.
De Weerd, P., Reithler, J., van de Ven, V., Been, M., Jacobs, C., & Sack, A. T. (2012). Posttraining transcranial magnetic stimulation of striate cortex disrupts consolidation early in visual skill learning. The Journal of Neuroscience, 32(6), 1981-1988. Retrieved from http://www.jneurosci.org/content/32/6/1981.long.
Fields, R. D. (2011, November 25). Amping up brain function: Transcranial stimulation shows promise in speeding up learning. Scientific American: Mind & Brain. Retrieved from http://www.scientificamerican.com/article/amping-up-brain-function/.
Flöel, A., Rösser, N., Michka, O., Knecht, S., & Breitenstein, C. (2008). Noninvasive brain stimulation improves language learning. Journal of Cognitive Neuroscience, 20(8), 1415-1422. Retrieved from http://www.researchgate.net/publication/5548486_Noninvasive_brain_stimulation_improves_language_learning/file/5046351db1c615613a.pdf.
Fregni, F., Boggio, P. S., Nitsche, M., Bermpohl, F., Antal, A., Feredoes, E.,… & Pascual-Leone, A. (2005). Anodal transcranial direct current stimulation of prefrontal cortex enhances working memory. Experimental Brain Research, 166(1), 23-30. Retrieved from http://www.researchgate.net/publication/7745540_Anodal_transcranial_direct_current_stimulation_of_prefrontal_cortex_enhances_working_memory/file/9fcfd50a3483033595.pdf.
Hamilton, R., Messing, S., & Chatterjee, A. (2011). Rethinking the thinking cap Ethics of neural enhancement using noninvasive brain stimulation. Neurology, 76(2), 187-193. Retrieved from http://wernicke.ccn.upenn.edu/~chatterjee/anjan_pdfs/Neurology_2011_HamiltonMessing_Chatterjee.pdf.
Jelić, M. B., Stevanović, V. B., Milanović, S. D., Ljubisavljević, M. R., & Filipović, S. R. (2013). Transcranial magnetic stimulation has no placebo effect on motor learning. Clinical Neurophysiology, 124(8). 1646-1651.
Kincses, T. Z., Antal, A., Nitsche, M. A., Bártfai, O., & Paulus, W. (2004). Facilitation of probabilistic classification learning by transcranial direct current stimulation of the prefrontal cortex in the human. Neuropsychologia, 42(1), 113-117. Retrieved from http://www.researchgate.net/publication/9011312_Facilitation_of_probabilistic_classification_learning_by_transcranial_direct_current_stimulation_of_the_prefrontal_cortex_in_the_human/file/d912f50597d44df446.pdf.
Koch, G., Franca, M., Mochizuki, H., Marconi, Caltagirone, & Rothwell. (2007). Interactions between pairs of transcranial magnetic stimuli over the human left dorsal premotor cortex differ from those seen in primary motor cortex. Journal of Physiology, 578, 551-562. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2075160/.
Mims, C. (2012, March 8). DIY kit overclocks your brain with direct current. Technology Review: View. Retrieved from http://www.technologyreview.com/view/427177/diy-kit-overclocks-your-brain-with-direct-current/.
Mix, A., Benali, A., Eysel, U. T., & Funke, K. (2010). Continuous and intermittent transcranial magnetic theta burst stimulation modify tactile learning performance and cortical protein expression in the rat differently. European Journal of Neuroscience, 32(9), 1575-1586.
Nitsche, M. A., Schauenburg, A., Lang, N., Liebetanz, D., Exner, C., Paulus, W., & Tergau, F. (2003). Facilitation of implicit motor learning by weak transcranial direct current stimulation of the primary motor cortex in the human. Journal of Cognitive Neuroscience, 15(4), 619-626. Retrieved from http://www.researchgate.net/publication/10710628_Facilitation_of_implicit_motor_learning_by_weak_transcranial_direct_current_stimulation_of_the_primary_motor_cortex_in_the_human/file/79e4150ae2024da0f0.pdf.
Ohn, S. H., Park, C. I., Yoo, W. K., Ko, M. H., Choi, K. P., Kim, G. M.,… & Kim, Y. H. (2008). Time-dependent effect of transcranial direct current stimulation on the enhancement of working memory. Neuroreport, 19(1), 43-47. Retrieved from http://diyhpl.us/~bryan/papers2/neuro/Time-dependent%20effect%20of%20transcranial%20direct%20current%20stimulation%20on%20the%20enhancement%20of%20working%20memory.pdf.
Oremus, W. (2013, April 1). Spark of genius. Slate: Technology: Superman. Retrieved from http://www.slate.com/articles/technology/superman/2013/04/tdcs_and_rtms_is_brain_stimulation_safe_and_effective.html.
Pascual-Leone, A., Valls-Solé, J., Wassermann, E. M., & Hallett, M. (1994). Responses to rapid-rate transcranial magnetic stimulation of the human motor cortex. Brain. 117(4), 847-858.
Perez, M. A., & Cohen, L. G. (in press as cited in Reis et al., 2008). Mechanisms underlying functional changes in the primary motor cortex ipsilateral to an active hand. Journal of Neuroscience.
Plewnia, C., Lotze, M., & Gerloff, C. (2003). Disinhibition of the contralateral motor cortex by low-frequency rTMS. Neuroreport, 14, 609-612.
Poreisz, C., Boros, K., Antal, A., & Paulus, W. (2007). Safety aspects of transcranial direct current stimulation concerning healthy subjects and patients. Brain Research Bulletin, 72(4), 208-214. Retrieved from http://www.researchgate.net/publication/6377248_Safety_aspects_of_transcranial_direct_current_stimulation_concerning_healthy_subjects_and_patients/file/9fcfd50a34830ccb05.pdf.
Reis, J., Robertson, E. M., Krakauer, J. W., Rothwell, J., Marshall, L., Gerloff, C.,… & Cohen, L. G. (2008). Consensus: Can transcranial direct current stimulation and transcranial magnetic stimulation enhance motor learning and memory formation?. Brain Stimulation, 1(4), 363-369. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2621080/.
Ruhr-University Bochum. (2011, January 29). Learn more quickly by transcranial magnetic brain stimulation, study in rats suggests. ScienceDaily. Retrieved February 10, 2014 from http://www.sciencedaily.com/releases/2011/01/110128121629.htm.
Schambra, H. M., Sawaki, L., & Cohen, L. G. (2003). Modulation of excitability of human motor cortex (M1) by 1 Hz transcranial magnetic stimulation of the contralateral M1. Clinical Neurophysiology, 114, 130-133.
Wall, C. A., Croarkin, P. E., McClintock, S. M., Murphy, L. L., Bandel, L. A., Sim, L. A., & Sampson, S. M. (2013). Neurocognitive effects of repetitive transcranial magnetic stimulation in adolescents with major depressive disorder. Frontiers in Psychiatry, 4(165). Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3859914/.
Wassermann, E. M., Wedegaertner, F. R., Ziemann, U., et al. (1998). Crossed reduction of human motor cortex excitability by 1-Hz transcranial magnetic stimulation. Neuroscience Letters, 250, 141-144.


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In: Neuropsychologia , Vol. 37, No. 2, 01.11.1998, p. 159-167.

Research output : Contribution to journal › Review article › peer-review

T1 - Transcranial magnetic stimulation can measure and modulate learning and memory

N2 - The potential uses for Transcranial Magnetic Stimulation (TMS) in the study of learning and memory range from a method to map the topography and intensity of motor output maps during visuomotor learning to inducing reversible lesions that allow for the precise temporal and spatial dissection of the brain processes underlying learning and remembering. Single-pulse TMS appears to be adequate to examine motor output maps but repetitive TMS (rTMS) appears necessary to affect most cognitive processes in measurable ways. The results we have reviewed in this article indicate that rTMS may have a potential clinical application in patients with epilepsy in whom it is important to identify the lateralization of verbal memory. Single-pulse TMS can help identify changes in motor output maps during training, that may indicate improved or diminished learning and memory processes following a stroke or other neurological insult. Other evidence indicates that rTMS may even have the capability of facilitating various aspects of memory performance. From a research perspective, rTMS has demonstrated site- and time-specific effects primarily in interfering with explicit retrieval of episodic information from long-term memory. rTMS may also be able to modulate retrieval from semantic memory as evidenced by response-time and accuracy changes after rTMS. All these findings suggest that the use of transcranial magnetic stimulation in the study of learning and memory will increase in the future and that it is already a valuable tool in the cognitive neuroscientists' belt.

AB - The potential uses for Transcranial Magnetic Stimulation (TMS) in the study of learning and memory range from a method to map the topography and intensity of motor output maps during visuomotor learning to inducing reversible lesions that allow for the precise temporal and spatial dissection of the brain processes underlying learning and remembering. Single-pulse TMS appears to be adequate to examine motor output maps but repetitive TMS (rTMS) appears necessary to affect most cognitive processes in measurable ways. The results we have reviewed in this article indicate that rTMS may have a potential clinical application in patients with epilepsy in whom it is important to identify the lateralization of verbal memory. Single-pulse TMS can help identify changes in motor output maps during training, that may indicate improved or diminished learning and memory processes following a stroke or other neurological insult. Other evidence indicates that rTMS may even have the capability of facilitating various aspects of memory performance. From a research perspective, rTMS has demonstrated site- and time-specific effects primarily in interfering with explicit retrieval of episodic information from long-term memory. rTMS may also be able to modulate retrieval from semantic memory as evidenced by response-time and accuracy changes after rTMS. All these findings suggest that the use of transcranial magnetic stimulation in the study of learning and memory will increase in the future and that it is already a valuable tool in the cognitive neuroscientists' belt.


Magnetic brain stimulation improves skill learning

The use of magnetic pulses to stimulate the dorsal premotor cortex (PMd) region of the brain results in an improved ability to learn a skilled motor task. Researchers writing in the open access journal BMC Neuroscience show that skilled movements can be stored as memories in the PMd and that magnetic stimulation of this area can facilitate this learning process. Lara Boyd and Meghan Linsdell, from the University of British Columbia, studied the effect of transcranial magnetic stimulation of the PMd on the ability of 30 volunteers to track a target on a computer screen using a joystick. During the task, the target would move randomly, then enter a programmed pattern and finally return to moving randomly. The participants were not aware of the repeated section, believing that movements were random throughout.

The volunteers received four days of training, during which they were either given excitatory stimulation, inhibitory stimulation or sham stimulation immediately before practicing the motor task. The volunteers were not aware which group they were in. On the fifth day, they were tested to see how well they had learned the task. By comparing the improvements between the random and repeated sections of the task, the researchers were able to separate the general improvement due to practice from the learned motor memory of the repeated section.

Those participants who had received the excitatory stimulation were significantly better than the other groups at tracking the target during the repeated section of the test. They showed no significant difference in improvement during the random sections. The researchers conclude, "Our data support the hypothesis that the PMd is important for continuous motor learning, specifically via off-line consolidation of learned motor behaviors".


Transcranial Direct Current Stimulation (tDCS)

Transcranial direct current stimulation (tDCS) is a neuro-modulatory technique that delivers low-intensity, direct current to cortical areas facilitating or inhibiting spontaneous neuronal activity. In the past ten years, tDCS physiological mechanisms of action have been intensively investigated giving support for the investigation of its applications in clinical neuropsychiatry and rehabilitation. Transcranial Direct Current Stimulation is a painless and non-invasive therapy that involves the delivery of mild electrical currents. In effect, these currents help stimulate certain areas of the brain.

How tDCS works
To begin the process of tDCS, two electrodes are placed over the head. Once the machine is fired up, constant low-intensity current (one to two mill amperes) is passed through the said electrodes for 10 to 20 minutes straight. The passing current then results in the modification neuronal activity. To prevent any adverse side effects, experts recommend allotting 48 hours before undergoing another round of tDCS.

  • tDCS is relatively painless and is non-invasive, so there is less downtime associated with pain and recovery.
  • tDCS is safe, effective with a low risk of adverse events
  • tDCS treatment can improve cognitive functions/speeding up learning processes.
  • tDCS can be helpful in treating Anxiety, Depression and regulating emotions.
  • Slight burning or mild tingling upon the application of electrical current.
  • Headache and nausea can also be expected, especially if the electrode is placed above the mastoid for the stimulation of the vestibular system.

Hopefully, continued research into and refinement of ECT, rTMS and tDCS will settle the subject. In the meantime, if you or a loved one is suffering from intractable mental illness, apart from medications, these three is something worth discussing with your Doctor/Psychiatrists/Mental health professionals.


Individual differences in TMS sensitivity influence the efficacy of tDCS in facilitating sensorimotor adaptation

Background: Transcranial direct current stimulation (tDCS) can enhance cognitive function in healthy individuals, with promising applications as a therapeutic intervention. Despite this potential, variability in the efficacy of tDCS has been a considerable concern.

Objective: /Hypothesis: Given that tDCS is always applied at a set intensity, we examined whether individual differences in sensitivity to brain stimulation might be one variable that modulates the efficacy of tDCS in a motor learning task.

Methods: In the first part of the experiment, single-pulse transcranial magnetic stimulation (TMS) over primary motor cortex (M1) was used to determine each participant's resting motor threshold (rMT). This measure was used as a proxy of individual sensitivity to brain stimulation. In an experimental group of 28 participants, 2 mA tDCS was then applied during a motor learning task with the anodal electrode positioned over left M1. Another 14 participants received sham stimulation.

Results: M1-Anodal tDCS facilitated learning relative to participants who received sham stimulation. Of primary interest was a within-group analysis of the experimental group, showing that the rate of learning was positively correlated with rMT: Participants who were more sensitive to brain stimulation as operationalized by our TMS proxy (low rMT), showed faster adaptation.

Conclusions: Methodologically, the results indicate that TMS sensitivity can predict tDCS efficacy in a behavioral task, providing insight into one source of variability that may contribute to replication problems with tDCS. Theoretically, the results provide further evidence of a role of sensorimotor cortex in adaptation, with the boost from tDCS observed during acquisition.

Keywords: Individual differences Sensorimotor learning TMS rMT tDCS.


Learn more quickly by transcranial magnetic brain stimulation

Top: Brain slice preparation through the frontal cortex of a rat showing nerve cells containing Parvalbumin (colored red) and surrounded by a perineural network (colored green) in untreated animals. Bottom: After treating the animals with the iTBS protocol, the Parvalbumin has disappeared to a great extent. The perineural network labeled by green dye that the cells still exist, but have not been destroyed by the stimulation. Credit: RUB

What sounds like science fiction is actually possible: thanks to magnetic stimulation, the activity of certain brain nerve cells can be deliberately influenced. What happens in the brain in this context has been unclear up to now. Medical experts from Bochum under the leadership of Prof. Dr. Klaus Funke (Department of Neurophysiology) have now shown that various stimulus patterns changed the activity of distinct neuronal cell types. In addition, certain stimulus patterns led to rats learning more easily.

The knowledge obtained could contribute to cerebral stimulation being used more purposefully in future to treat functional disorders of the brain. The researchers have published their studies in the Journal of Neuroscience and in the European Journal of Neuroscience.

Transcranial magnetic stimulation (TMS) is a relatively new method of pain-free stimulation of cerebral nerve cells. The method, which was presented by Anthony Barker for the first time in 1985, is based on the fact that the cortex, the rind of the brain located directly underneath the skull bone, can be stimulated by means of a magnetic field. TMS is applied in diagnostics, in fundamental research and also as a potential therapeutic instrument. Used in diagnostics, one single magnetic pulse serves to test the activability of nerve cells in an area of the cortex, in order to assess changes in diseases or after consumption of medications or also following a prior artificial stimulation of the brain. One single magnetic pulse can also serve to test the involvement of a certain area of the cortex in a sensorial, motoric or cognitive task, as it disturbs its natural activity for a short period, i.e. "switches off" the area on a temporary basis.

Since the mid-1990's, repetitive TMS has been used to make purposeful changes to the activability of nerve cells in the human cortex: "In general, the activity of the cells drops as a result of a low-frequency stimulation, i.e. with one magnetic pulse per second. At higher frequencies from five to 50 pulses per second, the activity of the cells increases", explained Prof. Funke. Above all, the researchers are specifically addressing with the effects of specific stimulus patterns like the so-called theta burst stimulation (TBS), in which 50 Hz bursts are repeated with 5 Hz. "This rhythm is based on the natural theta rhythm of four to seven Hertz which can be observed in an EEG", says Funke. The effect is above all dependent on whether such stimulus patterns are provided continuously (cTBS, attenuating effect) or with interruptions (intermittent, iTBS, strengthening effect).

It is unknown to a great extent how precisely the activity of nerve cells is changed by repeated stimulation. It is assumed that the contact points (synapses) between the cells are strengthened (synaptic potentation) or weakened (synaptic depression) as a result of the repeated stimulation, a process which also plays an important role in learning. Some time ago, it was also shown that the effects of TMS and learning interact in humans.

The researchers in Bochum have now shown for the first time that an artificial cortex stimulation specifically changes the activity of certain inhibitory nerve cells as a function of the stimulus protocol used. The balanced interaction of excitatory and inhibitory nerve cells is the absolute prerequisite for healthy functioning of the brain. Nerve cells specialised in inhibition of other nerve cells show a much greater variety in terms of cell shape and activity structure than their excitatory counterparts. Amongst other things, they produce various functional proteins in their cell body. In his studies, Prof. Funke has concentrated on the examination of the proteins Parvalbumin (PV), Calbindin-D28k (CB) and Calretinin (CR). They are formed by various inhibitory cells as a function of activity, with the result that their quantity gives information about the activity of the nerve cells in question.

For example, the examinations showed that activating stimulation protocol (iTBS) almost only reduces the PV content of the cells, whereas continuous stimulation attenuating activity (cTBS protocol), or a likewise attenuating 1 Hz stimulation, mainly reduces the CB production. CR formation was not changed by any of the tested stimulus protocols. Registration of the electrical activity of nerve cells confirmed a change in inhibition of the cortical activity.

In a second study, recently published in the European Journal of Neuroscience, Prof. Funke's group was able to show that rats also learned more quickly if they were treated with the activating stimulus protocol (iTBS) before each training, but not if the inhibiting cTBS protocol has been used. It was seen that the initially reduced formation of the protein Parvalbumin (PV) was increased again by the learning procedure, but only in the areas of the brain involved in the learning process. For animals not involved in the specific learning task, production of PV remained reduced following iTBS. "The iTBS treatment therefore initially reduces the activity of certain inhibiting nerve cells more generally, with the result that the following learning activities can be stored more easily," concludes Prof. Funke. "This process is termed "gating". In a second step, the learning activity restores the normal inhibition and PV production."

Repetitive TMS is already being used in clinical trials with limited success for therapy of functional disorders of the brain, above all in severe depressions. In addition, it was shown that especially disorders of the inhibitory nerve cells play an important role in neuropsychiatric diseases such as schizophrenia. "It is doubtless too early to derive new forms of treatment of functional disorders of the brain from the results of our study, but the knowledge obtained provides an important contribution for a possibly more specific application of TMS in future", is Prof. Funke's hope.


3. Cortical Excitability and Physical Exercise

In recent decades, in order to understand how the brain networks build and optimize motor programs, responsible for the different types of muscle activity and related coordination [41], numerous studies have been performed that included the use of neuroimaging and TMS [42,43]. The ability of TMS to stimulate deep neural structures, such as the motor cortex, has enabled researchers to investigate the integrity of the brain to muscle pathway and the functionality of cortical networks [44]. Since MEP are readily measurable by electromyographic recordings on peripheral muscles, the investigation of cortical excitability has become the focus of numerous studies. The brain reorganization in human is highly dependent on the specific behavioral demands of the training experience.

3.1. Skill Training

As showed by Pearce et al., highly skilled racket players show larger hand motor representation and also showed increase in MEP amplitudes compared with less proficient players and nonplaying controls [45]. Moreover, Tyc et al. show that highly skilled volleyball players showed significantly larger and more overlapping representations of medial deltoid and carpi radialis muscles, compared to runners [46]. Furthermore, TMS could be suitable for investigating the effect of acute motor exercise on the excitability of the motor pathway [47]. In fact, the augmented amplitudes of MEP have been reported as a result of acute exercise bouts, substantiating the increased neuronal excitability during fatigue.

3.2. Fatigue

In sport competition, fatigue has a large influence on performance. The term fatigue refers to any exercise inducing loss of ability to exert force or power with a muscle or a muscle group [46,47,48,49]. This phenomenon seems to be due to changes in the excitability of the motor pathway both at central and peripheral levels [50,51,52,53,54]. During the execution of maximal voluntary contractions, fatigue results from both peripheral and central factors, which play an important role in the decline of strength which results from a sub optimal output from the primary motor cortex, which ultimately leads to sub-optimal firing rates of motor neurons. On the other hand, when an incremental exhaustive exercise is performed, a rapid decrease in muscle phosphocreatine and ATP occurs and consequent accumulation of metabolites such as pyruvate and lactate [55,56,57]. There are few reports on TMS and fatigue in sports-specific motor activities.

3.3. Aerobic and Anaerobic Exercise

The first study to show the possible use of TMS in sports and various kinds of everyday exercises was undertaken by Hollge et al. [58]. This authors investigated the changes in muscle response and in central motor conduction times after aerobic (climbing stairs and jogging), and anaerobic (press-ups, dumb-bell holding, and 400 m run) exercises. Exhausting strength exercises resulted in an important decrement in muscle response measured by electromyography with an relative improvement in cortical excitability, while no significant changes were elicited by aerobic exercises [59,60,61,62,63]. Other authors [64] investigated the fatigue-induced change in the corticospinal drive to back muscles in elite rowers compared to an untrained subject. These authors found an improvement in cortical excitability in elite athletes. Recently, in different investigations, were reported that, the excitability in the primary hand motor cortex investigated with TMS, is enhanced at the end of a maximal incremental test and that this improvement strongly correlates with the increase in the blood lactate concentration [65,66]. However, recently study shows that an increase of blood lactate is correlated to an enhancement of the cortical excitability evaluated with TMS. In fact, after fatiguing hand-grip exercise, there was an increase in blood lactate with a significant decrease in rMT and MEP amplitude in a trained subject (taekwondo athletes) and in an untrained subject (non-athletes). Compared to pre-exercise values, blood lactate strongly increased at the end of exercise in each group, decline after 3’ min, and recovered to the pre-exercise value within 10 min. However, as expected, in non-athletes’ blood lactate increase strongly compared to athletes. In this investigation was showed that a voluntary sub-maximal tonic contraction is associated with a significant increase in blood lactate level. This increase in blood lactate was a consequence of the relatively small muscle mass involved in the exercise coupled to the low-level work done during grip [66,67,68,69,70,71]. Regarding the relationship between excitability and blood lactate, it has been suggested that when lactate increases due to strenuous exercise, the brain absorbs a similar amount to that of glucose. In this investigation, the reduction of rMT is maximal at the end of maximal exercise in parallel with the increase of blood lactate. Furthermore, also at the end of maximal exercise, and in parallel however non-athletes show higher depression of MEP amplitude compared to athletes at the end of exercise (�.97% vs. �.15%). Furthermore, in non-athletes, significant decrease emerged after 3 min of the end of exercise, while in athletes this differences disappeared. Therefore, it seems that, besides a possible role of exercise-elicited reduction of the blood flow in the cortex, the exercise-induced increase of blood lactate could be capable, in the frontal lobe, of worsening the performance in the prefrontal cortex and improving the excitability of motor cortex [72,73].


atDCS, anodal transcranial direct-current stimulation BDNF, brain-derived neurotrophic factor ctDCS, cathodal transcranial direct-current stimulation GABAA, γ-aminobutyric acid type A HD-tDCS, high-definition transcranial direct-current stimulation M1, primary motor cortex MEP, motor evoked potential NMDA, N-methyl-D-aspartate PFC, prefrontal cortex PM, premotor area RTs, reaction times SFTT, serial finger tapping tasks SMA, supplementary motor area SRTT, serial reaction time task SVIPT, sequential visual isometric pinch task tDCS, transcranial direct-current stimulation TMS, transcranial magnetic stimulation UDL, use-dependent learning.

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Keywords: transcranial electrical stimulation, tDCS, motor learning, non-invasive brain stimulation, plasticity, skill learning, motor adaptation, use-dependent learning

Citation: Ammann C, Spampinato D and Márquez-Ruiz J (2016) Modulating Motor Learning through Transcranial Direct-Current Stimulation: An Integrative View. Front. Psychol. 7:1981. doi: 10.3389/fpsyg.2016.01981

Received: 30 July 2016 Accepted: 05 December 2016
Published: 23 December 2016.

Nick J. Davis, Manchester Metropolitan University, UK

Charlotte K. Häger, Umeå University, Sweden
Bernadette Ann Murphy, University of Ontario Institute of Technology, Canada

Copyright © 2016 Ammann, Spampinato and Márquez-Ruiz. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.


Objectives

This experiment investigated the extent to which independent action observation, independent motor imagery and combined action observation and motor imagery of a sport-related motor skill elicited activity within the motor system.

Design and method

Eighteen, right-handed, male participants engaged in four conditions following a repeated measures design. The experimental conditions involved action observation, motor imagery, or combined action observation and motor imagery of a basketball free throw, whilst the control condition involved observation of a static image of a basketball player holding a basketball. In all conditions, single pulse transcranial magnetic stimulation was delivered to the forearm representation of the left motor cortex. The amplitude of the resulting motor evoked potentials were recorded from the flexor carpi ulnaris and extensor carpi ulnaris muscles of the right forearm and used as a marker of corticospinal excitability.

Results

Corticospinal excitability was facilitated significantly by combined action observation and motor imagery of the basketball free throw, in comparison to both the action observation and control conditions. In contrast, the independent use of either action observation or motor imagery did not facilitate corticospinal excitability compared to the control condition.

Conclusions

The findings have implications for the design and delivery of action observation and motor imagery interventions in sport. As corticospinal excitability was facilitated by the use of combined action observation and motor imagery, researchers should seek to establish the efficacy of implementing combined action observation and motor imagery interventions for improving motor skill performance and learning in applied sporting settings.


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In: Neuropsychologia , Vol. 37, No. 2, 01.11.1998, p. 159-167.

Research output : Contribution to journal › Review article › peer-review

T1 - Transcranial magnetic stimulation can measure and modulate learning and memory

N2 - The potential uses for Transcranial Magnetic Stimulation (TMS) in the study of learning and memory range from a method to map the topography and intensity of motor output maps during visuomotor learning to inducing reversible lesions that allow for the precise temporal and spatial dissection of the brain processes underlying learning and remembering. Single-pulse TMS appears to be adequate to examine motor output maps but repetitive TMS (rTMS) appears necessary to affect most cognitive processes in measurable ways. The results we have reviewed in this article indicate that rTMS may have a potential clinical application in patients with epilepsy in whom it is important to identify the lateralization of verbal memory. Single-pulse TMS can help identify changes in motor output maps during training, that may indicate improved or diminished learning and memory processes following a stroke or other neurological insult. Other evidence indicates that rTMS may even have the capability of facilitating various aspects of memory performance. From a research perspective, rTMS has demonstrated site- and time-specific effects primarily in interfering with explicit retrieval of episodic information from long-term memory. rTMS may also be able to modulate retrieval from semantic memory as evidenced by response-time and accuracy changes after rTMS. All these findings suggest that the use of transcranial magnetic stimulation in the study of learning and memory will increase in the future and that it is already a valuable tool in the cognitive neuroscientists' belt.

AB - The potential uses for Transcranial Magnetic Stimulation (TMS) in the study of learning and memory range from a method to map the topography and intensity of motor output maps during visuomotor learning to inducing reversible lesions that allow for the precise temporal and spatial dissection of the brain processes underlying learning and remembering. Single-pulse TMS appears to be adequate to examine motor output maps but repetitive TMS (rTMS) appears necessary to affect most cognitive processes in measurable ways. The results we have reviewed in this article indicate that rTMS may have a potential clinical application in patients with epilepsy in whom it is important to identify the lateralization of verbal memory. Single-pulse TMS can help identify changes in motor output maps during training, that may indicate improved or diminished learning and memory processes following a stroke or other neurological insult. Other evidence indicates that rTMS may even have the capability of facilitating various aspects of memory performance. From a research perspective, rTMS has demonstrated site- and time-specific effects primarily in interfering with explicit retrieval of episodic information from long-term memory. rTMS may also be able to modulate retrieval from semantic memory as evidenced by response-time and accuracy changes after rTMS. All these findings suggest that the use of transcranial magnetic stimulation in the study of learning and memory will increase in the future and that it is already a valuable tool in the cognitive neuroscientists' belt.


Magnetic Brain Stimulation Improves Skill Learning, Study Finds

The use of magnetic pulses to stimulate the dorsal premotor cortex (PMd) region of the brain results in an improved ability to learn a skilled motor task. Researchers show that skilled movements can be stored as memories in the PMd and that magnetic stimulation of this area can facilitate this learning process.

Lara Boyd and Meghan Linsdell, from the University of British Columbia, studied the effect of transcranial magnetic stimulation of the PMd on the ability of 30 volunteers to track a target on a computer screen using a joystick. During the task, the target would move randomly, then enter a programmed pattern and finally return to moving randomly. The participants were not aware of the repeated section, believing that movements were random throughout.

The volunteers received four days of training, during which they were either given excitatory stimulation, inhibitory stimulation or sham stimulation immediately before practicing the motor task. The volunteers were not aware which group they were in. On the fifth day, they were tested to see how well they had learned the task. By comparing the improvements between the random and repeated sections of the task, the researchers were able to separate the general improvement due to practice from the learned motor memory of the repeated section.

Those participants who had received the excitatory stimulation were significantly better than the other groups at tracking the target during the repeated section of the test. They showed no significant difference in improvement during the random sections. The researchers conclude, "Our data support the hypothesis that the PMd is important for continuous motor learning, specifically via off-line consolidation of learned motor behaviors".

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Materials provided by BioMed Central. Note: Content may be edited for style and length.


Magnetic Brain Stimulation Improves Skill Learning, Study Finds

The use of magnetic pulses to stimulate the dorsal premotor cortex (PMd) region of the brain results in an improved ability to learn a skilled motor task. Researchers show that skilled movements can be stored as memories in the PMd and that magnetic stimulation of this area can facilitate this learning process.

Lara Boyd and Meghan Linsdell, from the University of British Columbia, studied the effect of transcranial magnetic stimulation of the PMd on the ability of 30 volunteers to track a target on a computer screen using a joystick. During the task, the target would move randomly, then enter a programmed pattern and finally return to moving randomly. The participants were not aware of the repeated section, believing that movements were random throughout.

The volunteers received four days of training, during which they were either given excitatory stimulation, inhibitory stimulation or sham stimulation immediately before practicing the motor task. The volunteers were not aware which group they were in. On the fifth day, they were tested to see how well they had learned the task. By comparing the improvements between the random and repeated sections of the task, the researchers were able to separate the general improvement due to practice from the learned motor memory of the repeated section.

Those participants who had received the excitatory stimulation were significantly better than the other groups at tracking the target during the repeated section of the test. They showed no significant difference in improvement during the random sections. The researchers conclude, "Our data support the hypothesis that the PMd is important for continuous motor learning, specifically via off-line consolidation of learned motor behaviors".

Story Source:

Materials provided by BioMed Central. Note: Content may be edited for style and length.


atDCS, anodal transcranial direct-current stimulation BDNF, brain-derived neurotrophic factor ctDCS, cathodal transcranial direct-current stimulation GABAA, γ-aminobutyric acid type A HD-tDCS, high-definition transcranial direct-current stimulation M1, primary motor cortex MEP, motor evoked potential NMDA, N-methyl-D-aspartate PFC, prefrontal cortex PM, premotor area RTs, reaction times SFTT, serial finger tapping tasks SMA, supplementary motor area SRTT, serial reaction time task SVIPT, sequential visual isometric pinch task tDCS, transcranial direct-current stimulation TMS, transcranial magnetic stimulation UDL, use-dependent learning.

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Keywords: transcranial electrical stimulation, tDCS, motor learning, non-invasive brain stimulation, plasticity, skill learning, motor adaptation, use-dependent learning

Citation: Ammann C, Spampinato D and Márquez-Ruiz J (2016) Modulating Motor Learning through Transcranial Direct-Current Stimulation: An Integrative View. Front. Psychol. 7:1981. doi: 10.3389/fpsyg.2016.01981

Received: 30 July 2016 Accepted: 05 December 2016
Published: 23 December 2016.

Nick J. Davis, Manchester Metropolitan University, UK

Charlotte K. Häger, Umeå University, Sweden
Bernadette Ann Murphy, University of Ontario Institute of Technology, Canada

Copyright © 2016 Ammann, Spampinato and Márquez-Ruiz. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.


3. Cortical Excitability and Physical Exercise

In recent decades, in order to understand how the brain networks build and optimize motor programs, responsible for the different types of muscle activity and related coordination [41], numerous studies have been performed that included the use of neuroimaging and TMS [42,43]. The ability of TMS to stimulate deep neural structures, such as the motor cortex, has enabled researchers to investigate the integrity of the brain to muscle pathway and the functionality of cortical networks [44]. Since MEP are readily measurable by electromyographic recordings on peripheral muscles, the investigation of cortical excitability has become the focus of numerous studies. The brain reorganization in human is highly dependent on the specific behavioral demands of the training experience.

3.1. Skill Training

As showed by Pearce et al., highly skilled racket players show larger hand motor representation and also showed increase in MEP amplitudes compared with less proficient players and nonplaying controls [45]. Moreover, Tyc et al. show that highly skilled volleyball players showed significantly larger and more overlapping representations of medial deltoid and carpi radialis muscles, compared to runners [46]. Furthermore, TMS could be suitable for investigating the effect of acute motor exercise on the excitability of the motor pathway [47]. In fact, the augmented amplitudes of MEP have been reported as a result of acute exercise bouts, substantiating the increased neuronal excitability during fatigue.

3.2. Fatigue

In sport competition, fatigue has a large influence on performance. The term fatigue refers to any exercise inducing loss of ability to exert force or power with a muscle or a muscle group [46,47,48,49]. This phenomenon seems to be due to changes in the excitability of the motor pathway both at central and peripheral levels [50,51,52,53,54]. During the execution of maximal voluntary contractions, fatigue results from both peripheral and central factors, which play an important role in the decline of strength which results from a sub optimal output from the primary motor cortex, which ultimately leads to sub-optimal firing rates of motor neurons. On the other hand, when an incremental exhaustive exercise is performed, a rapid decrease in muscle phosphocreatine and ATP occurs and consequent accumulation of metabolites such as pyruvate and lactate [55,56,57]. There are few reports on TMS and fatigue in sports-specific motor activities.

3.3. Aerobic and Anaerobic Exercise

The first study to show the possible use of TMS in sports and various kinds of everyday exercises was undertaken by Hollge et al. [58]. This authors investigated the changes in muscle response and in central motor conduction times after aerobic (climbing stairs and jogging), and anaerobic (press-ups, dumb-bell holding, and 400 m run) exercises. Exhausting strength exercises resulted in an important decrement in muscle response measured by electromyography with an relative improvement in cortical excitability, while no significant changes were elicited by aerobic exercises [59,60,61,62,63]. Other authors [64] investigated the fatigue-induced change in the corticospinal drive to back muscles in elite rowers compared to an untrained subject. These authors found an improvement in cortical excitability in elite athletes. Recently, in different investigations, were reported that, the excitability in the primary hand motor cortex investigated with TMS, is enhanced at the end of a maximal incremental test and that this improvement strongly correlates with the increase in the blood lactate concentration [65,66]. However, recently study shows that an increase of blood lactate is correlated to an enhancement of the cortical excitability evaluated with TMS. In fact, after fatiguing hand-grip exercise, there was an increase in blood lactate with a significant decrease in rMT and MEP amplitude in a trained subject (taekwondo athletes) and in an untrained subject (non-athletes). Compared to pre-exercise values, blood lactate strongly increased at the end of exercise in each group, decline after 3’ min, and recovered to the pre-exercise value within 10 min. However, as expected, in non-athletes’ blood lactate increase strongly compared to athletes. In this investigation was showed that a voluntary sub-maximal tonic contraction is associated with a significant increase in blood lactate level. This increase in blood lactate was a consequence of the relatively small muscle mass involved in the exercise coupled to the low-level work done during grip [66,67,68,69,70,71]. Regarding the relationship between excitability and blood lactate, it has been suggested that when lactate increases due to strenuous exercise, the brain absorbs a similar amount to that of glucose. In this investigation, the reduction of rMT is maximal at the end of maximal exercise in parallel with the increase of blood lactate. Furthermore, also at the end of maximal exercise, and in parallel however non-athletes show higher depression of MEP amplitude compared to athletes at the end of exercise (�.97% vs. �.15%). Furthermore, in non-athletes, significant decrease emerged after 3 min of the end of exercise, while in athletes this differences disappeared. Therefore, it seems that, besides a possible role of exercise-elicited reduction of the blood flow in the cortex, the exercise-induced increase of blood lactate could be capable, in the frontal lobe, of worsening the performance in the prefrontal cortex and improving the excitability of motor cortex [72,73].


Magnetic brain stimulation improves skill learning

The use of magnetic pulses to stimulate the dorsal premotor cortex (PMd) region of the brain results in an improved ability to learn a skilled motor task. Researchers writing in the open access journal BMC Neuroscience show that skilled movements can be stored as memories in the PMd and that magnetic stimulation of this area can facilitate this learning process. Lara Boyd and Meghan Linsdell, from the University of British Columbia, studied the effect of transcranial magnetic stimulation of the PMd on the ability of 30 volunteers to track a target on a computer screen using a joystick. During the task, the target would move randomly, then enter a programmed pattern and finally return to moving randomly. The participants were not aware of the repeated section, believing that movements were random throughout.

The volunteers received four days of training, during which they were either given excitatory stimulation, inhibitory stimulation or sham stimulation immediately before practicing the motor task. The volunteers were not aware which group they were in. On the fifth day, they were tested to see how well they had learned the task. By comparing the improvements between the random and repeated sections of the task, the researchers were able to separate the general improvement due to practice from the learned motor memory of the repeated section.

Those participants who had received the excitatory stimulation were significantly better than the other groups at tracking the target during the repeated section of the test. They showed no significant difference in improvement during the random sections. The researchers conclude, "Our data support the hypothesis that the PMd is important for continuous motor learning, specifically via off-line consolidation of learned motor behaviors".


Transcranial Direct Current Stimulation (tDCS)

Transcranial direct current stimulation (tDCS) is a neuro-modulatory technique that delivers low-intensity, direct current to cortical areas facilitating or inhibiting spontaneous neuronal activity. In the past ten years, tDCS physiological mechanisms of action have been intensively investigated giving support for the investigation of its applications in clinical neuropsychiatry and rehabilitation. Transcranial Direct Current Stimulation is a painless and non-invasive therapy that involves the delivery of mild electrical currents. In effect, these currents help stimulate certain areas of the brain.

How tDCS works
To begin the process of tDCS, two electrodes are placed over the head. Once the machine is fired up, constant low-intensity current (one to two mill amperes) is passed through the said electrodes for 10 to 20 minutes straight. The passing current then results in the modification neuronal activity. To prevent any adverse side effects, experts recommend allotting 48 hours before undergoing another round of tDCS.

  • tDCS is relatively painless and is non-invasive, so there is less downtime associated with pain and recovery.
  • tDCS is safe, effective with a low risk of adverse events
  • tDCS treatment can improve cognitive functions/speeding up learning processes.
  • tDCS can be helpful in treating Anxiety, Depression and regulating emotions.
  • Slight burning or mild tingling upon the application of electrical current.
  • Headache and nausea can also be expected, especially if the electrode is placed above the mastoid for the stimulation of the vestibular system.

Hopefully, continued research into and refinement of ECT, rTMS and tDCS will settle the subject. In the meantime, if you or a loved one is suffering from intractable mental illness, apart from medications, these three is something worth discussing with your Doctor/Psychiatrists/Mental health professionals.


Learn more quickly by transcranial magnetic brain stimulation

Top: Brain slice preparation through the frontal cortex of a rat showing nerve cells containing Parvalbumin (colored red) and surrounded by a perineural network (colored green) in untreated animals. Bottom: After treating the animals with the iTBS protocol, the Parvalbumin has disappeared to a great extent. The perineural network labeled by green dye that the cells still exist, but have not been destroyed by the stimulation. Credit: RUB

What sounds like science fiction is actually possible: thanks to magnetic stimulation, the activity of certain brain nerve cells can be deliberately influenced. What happens in the brain in this context has been unclear up to now. Medical experts from Bochum under the leadership of Prof. Dr. Klaus Funke (Department of Neurophysiology) have now shown that various stimulus patterns changed the activity of distinct neuronal cell types. In addition, certain stimulus patterns led to rats learning more easily.

The knowledge obtained could contribute to cerebral stimulation being used more purposefully in future to treat functional disorders of the brain. The researchers have published their studies in the Journal of Neuroscience and in the European Journal of Neuroscience.

Transcranial magnetic stimulation (TMS) is a relatively new method of pain-free stimulation of cerebral nerve cells. The method, which was presented by Anthony Barker for the first time in 1985, is based on the fact that the cortex, the rind of the brain located directly underneath the skull bone, can be stimulated by means of a magnetic field. TMS is applied in diagnostics, in fundamental research and also as a potential therapeutic instrument. Used in diagnostics, one single magnetic pulse serves to test the activability of nerve cells in an area of the cortex, in order to assess changes in diseases or after consumption of medications or also following a prior artificial stimulation of the brain. One single magnetic pulse can also serve to test the involvement of a certain area of the cortex in a sensorial, motoric or cognitive task, as it disturbs its natural activity for a short period, i.e. "switches off" the area on a temporary basis.

Since the mid-1990's, repetitive TMS has been used to make purposeful changes to the activability of nerve cells in the human cortex: "In general, the activity of the cells drops as a result of a low-frequency stimulation, i.e. with one magnetic pulse per second. At higher frequencies from five to 50 pulses per second, the activity of the cells increases", explained Prof. Funke. Above all, the researchers are specifically addressing with the effects of specific stimulus patterns like the so-called theta burst stimulation (TBS), in which 50 Hz bursts are repeated with 5 Hz. "This rhythm is based on the natural theta rhythm of four to seven Hertz which can be observed in an EEG", says Funke. The effect is above all dependent on whether such stimulus patterns are provided continuously (cTBS, attenuating effect) or with interruptions (intermittent, iTBS, strengthening effect).

It is unknown to a great extent how precisely the activity of nerve cells is changed by repeated stimulation. It is assumed that the contact points (synapses) between the cells are strengthened (synaptic potentation) or weakened (synaptic depression) as a result of the repeated stimulation, a process which also plays an important role in learning. Some time ago, it was also shown that the effects of TMS and learning interact in humans.

The researchers in Bochum have now shown for the first time that an artificial cortex stimulation specifically changes the activity of certain inhibitory nerve cells as a function of the stimulus protocol used. The balanced interaction of excitatory and inhibitory nerve cells is the absolute prerequisite for healthy functioning of the brain. Nerve cells specialised in inhibition of other nerve cells show a much greater variety in terms of cell shape and activity structure than their excitatory counterparts. Amongst other things, they produce various functional proteins in their cell body. In his studies, Prof. Funke has concentrated on the examination of the proteins Parvalbumin (PV), Calbindin-D28k (CB) and Calretinin (CR). They are formed by various inhibitory cells as a function of activity, with the result that their quantity gives information about the activity of the nerve cells in question.

For example, the examinations showed that activating stimulation protocol (iTBS) almost only reduces the PV content of the cells, whereas continuous stimulation attenuating activity (cTBS protocol), or a likewise attenuating 1 Hz stimulation, mainly reduces the CB production. CR formation was not changed by any of the tested stimulus protocols. Registration of the electrical activity of nerve cells confirmed a change in inhibition of the cortical activity.

In a second study, recently published in the European Journal of Neuroscience, Prof. Funke's group was able to show that rats also learned more quickly if they were treated with the activating stimulus protocol (iTBS) before each training, but not if the inhibiting cTBS protocol has been used. It was seen that the initially reduced formation of the protein Parvalbumin (PV) was increased again by the learning procedure, but only in the areas of the brain involved in the learning process. For animals not involved in the specific learning task, production of PV remained reduced following iTBS. "The iTBS treatment therefore initially reduces the activity of certain inhibiting nerve cells more generally, with the result that the following learning activities can be stored more easily," concludes Prof. Funke. "This process is termed "gating". In a second step, the learning activity restores the normal inhibition and PV production."

Repetitive TMS is already being used in clinical trials with limited success for therapy of functional disorders of the brain, above all in severe depressions. In addition, it was shown that especially disorders of the inhibitory nerve cells play an important role in neuropsychiatric diseases such as schizophrenia. "It is doubtless too early to derive new forms of treatment of functional disorders of the brain from the results of our study, but the knowledge obtained provides an important contribution for a possibly more specific application of TMS in future", is Prof. Funke's hope.


Individual differences in TMS sensitivity influence the efficacy of tDCS in facilitating sensorimotor adaptation

Background: Transcranial direct current stimulation (tDCS) can enhance cognitive function in healthy individuals, with promising applications as a therapeutic intervention. Despite this potential, variability in the efficacy of tDCS has been a considerable concern.

Objective: /Hypothesis: Given that tDCS is always applied at a set intensity, we examined whether individual differences in sensitivity to brain stimulation might be one variable that modulates the efficacy of tDCS in a motor learning task.

Methods: In the first part of the experiment, single-pulse transcranial magnetic stimulation (TMS) over primary motor cortex (M1) was used to determine each participant's resting motor threshold (rMT). This measure was used as a proxy of individual sensitivity to brain stimulation. In an experimental group of 28 participants, 2 mA tDCS was then applied during a motor learning task with the anodal electrode positioned over left M1. Another 14 participants received sham stimulation.

Results: M1-Anodal tDCS facilitated learning relative to participants who received sham stimulation. Of primary interest was a within-group analysis of the experimental group, showing that the rate of learning was positively correlated with rMT: Participants who were more sensitive to brain stimulation as operationalized by our TMS proxy (low rMT), showed faster adaptation.

Conclusions: Methodologically, the results indicate that TMS sensitivity can predict tDCS efficacy in a behavioral task, providing insight into one source of variability that may contribute to replication problems with tDCS. Theoretically, the results provide further evidence of a role of sensorimotor cortex in adaptation, with the boost from tDCS observed during acquisition.

Keywords: Individual differences Sensorimotor learning TMS rMT tDCS.


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In: Neuropsychologia , Vol. 37, No. 2, 01.11.1998, p. 159-167.

Research output : Contribution to journal › Review article › peer-review

T1 - Transcranial magnetic stimulation can measure and modulate learning and memory

N2 - The potential uses for Transcranial Magnetic Stimulation (TMS) in the study of learning and memory range from a method to map the topography and intensity of motor output maps during visuomotor learning to inducing reversible lesions that allow for the precise temporal and spatial dissection of the brain processes underlying learning and remembering. Single-pulse TMS appears to be adequate to examine motor output maps but repetitive TMS (rTMS) appears necessary to affect most cognitive processes in measurable ways. The results we have reviewed in this article indicate that rTMS may have a potential clinical application in patients with epilepsy in whom it is important to identify the lateralization of verbal memory. Single-pulse TMS can help identify changes in motor output maps during training, that may indicate improved or diminished learning and memory processes following a stroke or other neurological insult. Other evidence indicates that rTMS may even have the capability of facilitating various aspects of memory performance. From a research perspective, rTMS has demonstrated site- and time-specific effects primarily in interfering with explicit retrieval of episodic information from long-term memory. rTMS may also be able to modulate retrieval from semantic memory as evidenced by response-time and accuracy changes after rTMS. All these findings suggest that the use of transcranial magnetic stimulation in the study of learning and memory will increase in the future and that it is already a valuable tool in the cognitive neuroscientists' belt.

AB - The potential uses for Transcranial Magnetic Stimulation (TMS) in the study of learning and memory range from a method to map the topography and intensity of motor output maps during visuomotor learning to inducing reversible lesions that allow for the precise temporal and spatial dissection of the brain processes underlying learning and remembering. Single-pulse TMS appears to be adequate to examine motor output maps but repetitive TMS (rTMS) appears necessary to affect most cognitive processes in measurable ways. The results we have reviewed in this article indicate that rTMS may have a potential clinical application in patients with epilepsy in whom it is important to identify the lateralization of verbal memory. Single-pulse TMS can help identify changes in motor output maps during training, that may indicate improved or diminished learning and memory processes following a stroke or other neurological insult. Other evidence indicates that rTMS may even have the capability of facilitating various aspects of memory performance. From a research perspective, rTMS has demonstrated site- and time-specific effects primarily in interfering with explicit retrieval of episodic information from long-term memory. rTMS may also be able to modulate retrieval from semantic memory as evidenced by response-time and accuracy changes after rTMS. All these findings suggest that the use of transcranial magnetic stimulation in the study of learning and memory will increase in the future and that it is already a valuable tool in the cognitive neuroscientists' belt.


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  • APA
  • Author
  • BIBTEX
  • Harvard
  • Standard
  • RIS
  • Vancouver

In: Neuropsychologia , Vol. 37, No. 2, 01.11.1998, p. 159-167.

Research output : Contribution to journal › Review article › peer-review

T1 - Transcranial magnetic stimulation can measure and modulate learning and memory

N2 - The potential uses for Transcranial Magnetic Stimulation (TMS) in the study of learning and memory range from a method to map the topography and intensity of motor output maps during visuomotor learning to inducing reversible lesions that allow for the precise temporal and spatial dissection of the brain processes underlying learning and remembering. Single-pulse TMS appears to be adequate to examine motor output maps but repetitive TMS (rTMS) appears necessary to affect most cognitive processes in measurable ways. The results we have reviewed in this article indicate that rTMS may have a potential clinical application in patients with epilepsy in whom it is important to identify the lateralization of verbal memory. Single-pulse TMS can help identify changes in motor output maps during training, that may indicate improved or diminished learning and memory processes following a stroke or other neurological insult. Other evidence indicates that rTMS may even have the capability of facilitating various aspects of memory performance. From a research perspective, rTMS has demonstrated site- and time-specific effects primarily in interfering with explicit retrieval of episodic information from long-term memory. rTMS may also be able to modulate retrieval from semantic memory as evidenced by response-time and accuracy changes after rTMS. All these findings suggest that the use of transcranial magnetic stimulation in the study of learning and memory will increase in the future and that it is already a valuable tool in the cognitive neuroscientists' belt.

AB - The potential uses for Transcranial Magnetic Stimulation (TMS) in the study of learning and memory range from a method to map the topography and intensity of motor output maps during visuomotor learning to inducing reversible lesions that allow for the precise temporal and spatial dissection of the brain processes underlying learning and remembering. Single-pulse TMS appears to be adequate to examine motor output maps but repetitive TMS (rTMS) appears necessary to affect most cognitive processes in measurable ways. The results we have reviewed in this article indicate that rTMS may have a potential clinical application in patients with epilepsy in whom it is important to identify the lateralization of verbal memory. Single-pulse TMS can help identify changes in motor output maps during training, that may indicate improved or diminished learning and memory processes following a stroke or other neurological insult. Other evidence indicates that rTMS may even have the capability of facilitating various aspects of memory performance. From a research perspective, rTMS has demonstrated site- and time-specific effects primarily in interfering with explicit retrieval of episodic information from long-term memory. rTMS may also be able to modulate retrieval from semantic memory as evidenced by response-time and accuracy changes after rTMS. All these findings suggest that the use of transcranial magnetic stimulation in the study of learning and memory will increase in the future and that it is already a valuable tool in the cognitive neuroscientists' belt.


Objectives

This experiment investigated the extent to which independent action observation, independent motor imagery and combined action observation and motor imagery of a sport-related motor skill elicited activity within the motor system.

Design and method

Eighteen, right-handed, male participants engaged in four conditions following a repeated measures design. The experimental conditions involved action observation, motor imagery, or combined action observation and motor imagery of a basketball free throw, whilst the control condition involved observation of a static image of a basketball player holding a basketball. In all conditions, single pulse transcranial magnetic stimulation was delivered to the forearm representation of the left motor cortex. The amplitude of the resulting motor evoked potentials were recorded from the flexor carpi ulnaris and extensor carpi ulnaris muscles of the right forearm and used as a marker of corticospinal excitability.

Results

Corticospinal excitability was facilitated significantly by combined action observation and motor imagery of the basketball free throw, in comparison to both the action observation and control conditions. In contrast, the independent use of either action observation or motor imagery did not facilitate corticospinal excitability compared to the control condition.

Conclusions

The findings have implications for the design and delivery of action observation and motor imagery interventions in sport. As corticospinal excitability was facilitated by the use of combined action observation and motor imagery, researchers should seek to establish the efficacy of implementing combined action observation and motor imagery interventions for improving motor skill performance and learning in applied sporting settings.



Comments:

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