Posts Tagged Transcranial magnetic stimulation

[BLOG POST] tES vs. TMS: pros and cons of the two techniques

tms-vs-tes

At Neuroelectrics, we believe in the advantages and effectiveness of transcranial electric stimulation (tES) in treating numerous brain diseases. Yet, despite the increasing number of tES publications per year, the lion’s share in the market of non-invasive brain stimulation technologies is still played by transcranial magnetic stimulation (TMS), likely because TMS received US-FDA approval in 2008 whereas tES has not yet.

Does this mean TMS is more effective? Well, it’s not quite fair to say so, considering TMS studies started at least 10 years earlier than those of tES. Therefore, there are several more clinical trials proving TMS efficacy.

However, the two techniques are close relatives: you can think of TMS as the elderly, stiff and sturdy brother, and tES as the younger, more flexible and easy-going one.
In this blogpost, we’ll go over the roots of their differences and see when and why you might prefer one over the other.

[E-fields patterns and biophysical substrates]

At a fundamental level, the two techniques rely on different physics and induce distinct patterns of electric fields (E-field) on the cortex, acting on a different neural substrate.

TMS is based on electromagnetic induction: a large magnetic coil is placed just a few centimetres above the scalp to stimulate over a specific cortical area. When the operator launches the electric pulse, vast amounts of current flows suddenly through the coil and creates a magnetic field around it, which varies rapidly in time. This changing magnetic field induces a very short (order of 1ms), highly localized (figure 1), super-threshold (order of 100V/m) E-field in the cortex. The E-field maximum is reached on the gyrus right under the coil, and the orientation is mostly parallel to the cortical surface.
The most sensitive cells to an E-field with such characteristics are interneurons and collaterals of pyramidal cells aligned tangentially to the cortical surface, which are automatically triggered to fire.

Instead, tES operates in the (quasi-)static regime, as only a small amount of direct current (DC) or low frequency alternating current (AC) is applied through electrodes placed directly on the scalp. The temporal resolution of the technique is low because the neuromodulatory effects begins a few seconds after the start of stimulation. Moreover, the E-field generated is much weaker (order of 0.1V/m) and less focalized (although the focality can be improved by using multichannel montages, it remains much lower than TMS E-field). Depending on the electrodes’ geometry, the maxima can occur on the gyri at the edges of the electrodes or between them. The overall orientation of the E-field is normal to the cortical surface, which indicates that tES probably influences layer V pyramidal neurons, as they are mostly perpendicular to the cortex.

Given the low, subthreshold intensity, the tES E-field cannot cause neural firing, but it is able to modulate the firing rate, facilitating or inhibiting the activation of pyramidal cells.

[Devices]

Other important differences concerning system setup.

TMS technology is more complex and cumbersome. The cost of the whole equipment is between 50-100k USD or Euros. This includes a wall-powered and heavy stimulator about the size of a fridge, a coil connected to the stimulator by a high-voltage cable, a mechanical arm to hold it in place, and a neuro-navigation system to accurately place the coil over the target brain region. The coil hangs suspended over the head of the patient, and since the strength of the effects depends on the coil-cortex distance, it’s crucial to keep it at the specific distance. For this, during the treatment session, the patient must sit still in a specially designed chair, with positioning frames around the chin and forehead.

On the contrary, tES is much cheaper and effortless: the cost is between an average of 6-30k USD/Euros, and the whole setup fits a shoe box. The stimulator can be as small as a mobile phone, light/portable, and almost always battery powered. The electrodes are directly in contact with the scalp, held in place by a rubber band or a neoprene cap. This way, the patient can move and even walk during the stimulation session.

[Applications]

Despite the underlying differences, TMS and tES are both quite versatile tools for treatment and research, and they offer similar options.

In research settings, you can leverage on TMS’ high spatial and temporal resolution to study how brain networks dynamically operate. In this context, TMS is usually performed online (during task performance) by applying one pulse at the onset of a stimulus (single-pulse TMS), or two pulses over separate regions which are interconnected (paired-pulses TMS). But tES too allows one to study the causal link between cortical areas. For instance, with tACS, one can simultaneously apply oscillatory currents over distinct regions at the same frequency but with different phases to promote or hamper the synchronization of functional networks.

Clinical applications of brain stimulation techniques instead tend to focus more on long-term effects, promoting network neuroplasticity that can outlast the period of stimulation.
In this case, TMS is usually ran in the repetitive mode (rTMS), which consists in multiple pulses within just microseconds. Frequency lower than 1Hz has been linked to long term depression (LTD), whereas frequency above 5Hz to long term potentiation (LTP). Similar outcomes can be achieved with tCS using either tDCS anodal or cathodal stimulation, which has been shown promoting and inhibiting synaptic activation, respectively.

The side effects of both techniques are quite moderate – with one important exception. While tES can induce only mild and temporary itching, tingling, and skin reddening when done properly, TMS might cause mild headaches, facial twitching, seizures in extreme cases.

For both TMS and tES, medical treatment must be performed mostly in clinical settings, which means you will have to find a clinician who provides these services in their clinic. However, one of the strengths of tES is the possibility to perform stimulation telemedically (under the remote guidance of a clinicians) via home-treatment. This is important as it will boost therapeutic effects for pathologies such as motor rehabilitation, depression, Alzheimer’s disease, etc in the comfort of one’s home. And it has been shown that the number of sessions modulates the length of the long-term plastic effects.

Interested in home-application of tCS? Check our home-kit here.

tes-vs-tms

Figure 1 Distribution of the E-field magnitude on the GM surface (left) and on a midsagittal slice (right) during TMS (A,C) and tDCS  with 35cm2 rectangular sponges (B, D). E-field magnitude is in V/m. Courtesy of Salvador et. al. 2015

[REFERENCES]

Polanía R, Nitsche M.A., Ruff C., Studying and modifying brain function with non-invasive brain stimulation, Nat. neurosci., 21:174–187 (2018)

Dayan E., Censor N., Buch E.R., Sandrini M, Cohen L.G., Noninvasive brain stimulation: from physiology to network dynamics and back, Nat. Neurosci., 16:838–844 (2013)

Salvador R., Wenger C., Miranda P.C. Investigating the cortical regions involved in MEP modulation in tDCS, Front. Cell. Neurosci. 9:405 (2015)

thebrainstimulator.net/brain-stimulation-comparison/caputron.com/pages/tms-vs-tdcs

 

via tES vs. TMS: pros and cons of the two techniques – Blog Neuroelectrics

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[Abstract] The effects of a robot-assisted arm training plus hand functional electrical stimulation on recovery after stroke: a randomized clinical trial

Abstract

Objective

To compare the effects of unilateral, proximal arm robot-assisted therapy combined with hand functional electrical stimulation to intensive conventional therapy for restoring arm function in subacute stroke survivors.

Design

This was a single blinded, randomized controlled trial.

Setting

Inpatient Rehabilitation University Hospital.

Participants

Forty patients diagnosed with ischemic stroke (time since stroke <8 weeks) and upper limb impairment were enrolled.

Interventions

Participants randomized to the experimental group received 30 sessions (5 sessions/week) of robot-assisted arm therapy and hand functional electrical stimulation (RAT + FES). Participants randomized to the control group received a time-matched intensive conventional therapy (ICT).

Main outcome measures

The primary outcome was arm motor recovery measured with the Fugl-Meyer Motor Assessment. Secondary outcomes included motor function, arm spasticity and activities of daily living. Measurements were performed at baseline, after 3 weeks, at the end of treatment and at 6-month follow-up. Presence of motor evoked potentials (MEPs) was also measured at baseline.

Results

Both groups significantly improved all outcome measures except for spasticity without differences between groups. Patients with moderate impairment and presence of MEPs who underwent early rehabilitation (<30 days post stroke) demonstrated the greatest clinical improvements.

Conclusions

A robot-assisted arm training plus hand functional electrical stimulation was no more effective than intensive conventional arm training. However, at the same level of arm impairment and corticospinal tract integrity, it induced a higher level of arm recovery.

 

via The effects of a robot-assisted arm training plus hand functional electrical stimulation on recovery after stroke: a randomized clinical trial – ScienceDirect

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[WEB SITE] Depression Overview: Emotional Symptoms, Physical Signs, and More – WebMD

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[Abstract] Role of Interhemispheric Cortical Interactions in Poststroke Motor Function

Background/Objective. We investigated interhemispheric interactions in stroke survivors by measuring transcranial magnetic stimulation (TMS)–evoked cortical coherence. We tested the effect of TMS on interhemispheric coherence during rest and active muscle contraction and compared coherence in stroke and older adults. We evaluated the relationships between interhemispheric coherence, paretic motor function, and the ipsilateral cortical silent period (iSP).

Methods. Participants with (n = 19) and without (n = 14) chronic stroke either rested or maintained a contraction of the ipsilateral hand muscle during simultaneous recordings of evoked responses to TMS of the ipsilesional/nondominant (i/ndM1) and contralesional/dominant (c/dM1) primary motor cortex with EEG and in the hand muscle with EMG. We calculated pre- and post-TMS interhemispheric beta coherence (15-30 Hz) between motor areas in both conditions and the iSP duration during the active condition.

Results. During active i/ndM1 TMS, interhemispheric coherence increased immediately following TMS in controls but not in stroke. Coherence during active cM1 TMS was greater than iM1 TMS in the stroke group. Coherence during active iM1 TMS was less in stroke participants and was negatively associated with measures of paretic arm motor function. Paretic iSP was longer compared with controls and negatively associated with clinical measures of manual dexterity. There was no relationship between coherence and. iSP for either group. No within- or between-group differences in coherence were observed at rest.

Conclusions. TMS-evoked cortical coherence during hand muscle activation can index interhemispheric interactions associated with poststroke motor function and potentially offer new insights into neural mechanisms influencing functional recovery.

 

via Role of Interhemispheric Cortical Interactions in Poststroke Motor Function – Jacqueline A. Palmer, Lewis A. Wheaton, Whitney A. Gray, Mary Alice Saltão da Silva, Steven L. Wolf, Michael R. Borich, 2019

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[Abstract] Differential Poststroke Motor Recovery in an Arm Versus Hand Muscle in the Absence of Motor Evoked Potentials

Background. After stroke, recovery of movement in proximal and distal upper extremity (UE) muscles appears to follow different time courses, suggesting differences in their neural substrates.

Objective. We sought to determine if presence or absence of motor evoked potentials (MEPs) differentially influences recovery of volitional contraction and strength in an arm muscle versus an intrinsic hand muscle. We also related MEP status to recovery of proximal and distal interjoint coordination and movement fractionation, as measured by the Fugl-Meyer Assessment (FMA).

Methods. In 45 subjects in the year following ischemic stroke, we tracked the relationship between corticospinal tract (CST) integrity and behavioral recovery in the biceps (BIC) and first dorsal interosseous (FDI) muscle. We used transcranial magnetic stimulation to probe CST integrity, indicated by MEPs, in BIC and FDI. We used electromyography, dynamometry, and UE FMA subscores to assess muscle-specific contraction, strength, and inter-joint coordination, respectively.

Results. Presence of MEPs resulted in higher likelihood of muscle contraction, greater strength, and higher FMA scores. Without MEPs, BICs could more often volitionally contract, were less weak, and had steeper strength recovery curves than FDIs; in contrast, FMA recovery curves plateaued below normal levels for both the arm and hand.

Conclusions. There are shared and separate substrates for paretic UE recovery. CST integrity is necessary for interjoint coordination in both segments and for overall recovery. In its absence, alternative pathways may assist recovery of volitional contraction and strength, particularly in BIC. These findings suggest that more targeted approaches might be needed to optimize UE recovery.

 

via Differential Poststroke Motor Recovery in an Arm Versus Hand Muscle in the Absence of Motor Evoked Potentials – Heidi M. Schambra, Jing Xu, Meret Branscheidt, Martin Lindquist, Jasim Uddin, Levke Steiner, Benjamin Hertler, Nathan Kim, Jessica Berard, Michelle D. Harran, Juan C. Cortes, Tomoko Kitago, Andreas Luft, John W. Krakauer, Pablo A. Celnik, 2019

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[Abstract] Publication trends in transcranial magnetic stimulation: A 30-year panorama

Highlights

  • This study uses a systematic, bibliometric approach to assess the TMS literature base.
  • Annual TMS research output has increased dramatically over the period 1988–2017.
  • The top disease entities studied to date have been stroke and depression.

 

Abstract

Background

Transcranial magnetic stimulation (TMS) is a non-invasive neuromodulatory technique that has broad diagnostic and therapeutic potential across a range of neurological and psychiatric diseases.

Objective

This study utilises a bibliometric approach to systematically and comprehensively evaluate the literature on TMS from the last three decades.

Methods

The Scopus citation database was used to identify all peer-reviewed journal articles concerning TMS over the period 1988–2017. Frequency-distribution, cross-tabulation and keyword analyses were performed to determine the most prolific researchers, institutions, nations, journals and the foremost studied disease entities within the TMS field. Given recent heightened awareness of gender bias across many fields of biomedicine, female representation among the most prolific authors was determined. Open-access publication rates and types of study design utilised were also quantified.

Results

17,492 TMS-related articles were published during the study period 1988–2017. The annual TMS research output has increased dramatically over this time, despite a recent levelling-off of publications per year. The most prolific institutions were based in the United Kingdom, the United States and Canada. The top disease entities studied were stroke, depression and Parkinson’s disease. Only 4/52 of the most productive researchers during the study period were female. A minority (4.81%) of publications were published as gold open-access.

Conclusion

This study implemented a systematic, bibliometric approach to quantitively assess the breadth of the TMS literature base and identify temporal publication and authorship trends. Drawing on these insights may aid understanding of historical progress in TMS over the last 30 years and help identify into unmet needs and opportunities to improve scientific and publishing practices to contribute to the future health of the field. These findings are likely to be relevant to researchers, clinicians, funders, industry collaborators and other stakeholders.

 

via Publication trends in transcranial magnetic stimulation: A 30-year panorama – Brain Stimulation: Basic, Translational, and Clinical Research in Neuromodulation

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[WEB SITE] Transcranial Magnetic Stimulation for the Recovery of Gait and Balance in Stroke Patients – BrainPost

Post by Thomas Brown

What’s the science?

The permanent brain damage which occurs following ischemic stroke makes functional recovery difficult. While physiotherapy can result in improved voluntary motor recovery, the improvement of balance and gait can be harder. Issues with balance pose a safety risk for stroke patients, who may be more likely to fall. Ultimately, problems with balance can mean reduced independence for patients. The cerebellum, a structure located at the back of the brain, is known to regulate movement, gait and balance. Deficits to the cerebellum often result in ataxia and widened gaits, making this area a prime target for functional recovery analysis. This week in JAMA Neurology Koch and colleagues demonstrate in a phase IIa clinical trial, an increase in gait and balance in hemiparetic stroke patients, up to three weeks after physiotherapy supplemented with transcranial magnetic stimulation of the cerebellum.

How did they do it?

A group of 36 hemiparetic (one side affected) stroke patients were randomly assigned to one of two age-matched groups; control or experimental. The experimental group was treated with intermittent theta-burst magnetic stimulation (TBS) of the cerebellar region ipsilateral (same side) to their motor issues. Intermittent TBS is a process by which bursts of magnetic energy are applied to the scalp over an area of interest. TBS was administered in conjunction with physiotherapy to the experimental group for three weeks. The control group still received physiotherapy, but received sham (fake) TBS. Patients were assessed using a wide range of balance and gait analysis tests to determine the degree of recovery. The authors relied primarily on the Berg Balance Scale, which is a series of 14 tests that determine the ability of an individual to balance without aid. Gait analysis was also performed, in which patients were asked to walk while a machine measured their gait (the space between each foot while walking). Neural activity was measured with electroencephalography while transcranial magnetic stimulation was applied simultaneously (EEG-TMS). This technique was used to measure neural activity changes in motor regions of the brain following activation of the motor cortex using a different TMS paradigm than the one used for treatment.

What did they find?

The authors found that after three weeks of the last treatment with either sham or cerebellar TBS, there was an average increase in the Berg Balance Scale score in those treated with TBS compared to controls. They also showed a reduction in gait width; a wide gait is often associated with the body’s attempt to compensate for problems with balance. This finding was supported by correlational analysis which found that a reduction is step width was associated with an improvement in Berg Balance Scale score. Interestingly, three weeks after treatment there was also an increase in neural activity in the motor (M1) region of the brain in the hemispheres affected by the stoke, in treated patients compared to controls. This area of the cortex is associated with the movement execution. Altogether these findings suggest that there were significant balance, gait and motor cortex activity improvements following treatment with TBS. Critically, no adverse effects were observed following treatment with TBS during the clinical trial.

stroke_image.png

What’s the impact?

These findings suggest that theta-burst stimulation may be an effective way of supplementing physiotherapy in those suffering with balance and gait deficits following stroke. Theta-burst stimulation in conjunction with physiotherapy, was able to improve both balance and gait in stroke patients. Treatment with theta-burst stimulation could reduce the chance of falling and improve independence in stroke patients.

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Koch et al. Effect of Cerebellar Stimulation on Gait and Balance Recovery
in Patients With Hemiparetic Stroke. JAMA Neurology (2018).Access the original scientific publication here

 

via Weekly BrainPost — BrainPost

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[ARTICLE] Noninvasive Brain Stimulation to Enhance Functional Recovery After Stroke: Studies in Animal Models – Full Text

Background. Stroke is the leading cause of adult disability, but treatment options remain limited, leaving most patients with incomplete recovery. Patient and animal studies have shown potential of noninvasive brain stimulation (NIBS) strategies to improve function after stroke. However, mechanisms underlying therapeutic effects of NIBS are unclear and there is no consensus on which NIBS protocols are most effective.

Objective. Provide a review of articles that assessed effects and mechanisms of repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) in animal stroke models.

Methods. Articles were searched in PubMed, including cross-references.

Results. Nineteen eligible studies reporting effects of rTMS or tDCS after stroke in small rodents were identified. Seventeen of those described improved functional recovery or neuroprotection compared with untreated control or sham-stimulated groups. The effects of rTMS could be related to molecular mechanisms associated with ischemic tolerance, neuroprotection, anti-apoptosis, neurogenesis, angiogenesis, or neuroplasticity. Favorable outcome appeared most effectively when using high-frequency (>5 Hz) rTMS or intermittent theta burst stimulation of the ipsilesional hemisphere. tDCS effects were strongly dependent on stimulation polarity and onset time. Although these findings are promising, most studies did not meet Good Laboratory Practice assessment criteria.

Conclusions. Despite limited data availability, animal stroke model studies demonstrate potential of NIBS to promote stroke recovery through different working mechanisms. Future studies in animal stroke models should adhere to Good Laboratory Practice guidelines and aim to further develop clinically applicable treatment protocols by identifying most favorable stimulation parameters, treatment onset, adjuvant therapies, and underlying modes of action.

Globally, stroke is a devastating neurological disorder and a leading cause of death and acquired disability.1 The majority of stroke patients experience motor impairment, which affects movement of the face, leg, and/or arm on one side of the body.2 Upper limb motor deficiencies are often persistent and disabling, affecting independent functional activities of daily living.3 Unfortunately, most stroke patients recover incompletely after stroke, despite intensive rehabilitation strategies.3,4 Although there is a diverse range of interventions (for overview, see review by Pollock and colleagues4) aimed at improving motor outcome after stoke, there is still a pressing need for novel treatment therapies and continued research to reduce disability and improve functional recovery after stroke.

Noninvasive brain stimulation (NIBS) techniques, such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), have shown promising therapeutic potential in stroke patient studies.5,6 The rationale behind rTMS or tDCS therapy is to modulate cortical excitability, increase neural plasticity, and improve functional motor outcome. For many studies, this approach has been based on the interhemispheric competition model.7 The interhemispheric competition model suggests that functional recovery in stroke patients is hindered due to reduced output from the affected hemisphere and excessive transcallosal inhibition from the unaffected hemisphere.8 Therefore, improvement in motor deficits may be obtained with NIBS strategies that facilitate excitability in the affected hemisphere or suppress inhibitory activity from the unaffected hemisphere.9,10 Depending on the type and duration of the stimulation protocol, both rTMS and tDCS can be used to increase (>5 Hz rTMS; intermittent theta burst stimulation; anodal tDCS) or decrease (⩽1 Hz rTMS; continuous theta burst stimulation; cathodal tDCS) cortical excitability, with potentially lasting effects beyond the stimulation period, promoting mechanisms of synaptic plasticity.11 Evidence suggests that rTMS and tDCS techniques are able to induce changes in cortical excitability associated with facilitation or long-term potentiation like plasticity via glutamatergic neurotransmission, or inhibition and long-term depression via GABAergic neurotransmission.12,13 Furthermore, effects of rTMS and tDCS are not restricted to the target region of stimulation, but also affect distantly connected cortical areas, allowing for the modulation of large-scale neural networks.14

However, despite accumulating evidence of the potential of NIBS, the precise therapeutic mechanisms of action of rTMS and tDCS are largely unidentified and there is no consensus about standardized treatment protocols. Moreover, when deciding on treatment after stroke with either rTMS or tDCS, the poststroke time and lesion status should be considered, and stimulation intensity and duration must be fine-tuned to prevent further tissue damage or the interruption of beneficial plastic changes.15,16 These uncertainties emphasize the critical need for basic understanding of the (patho)physiological processes that are influenced by rTMS and tDCS paradigms after stroke, which may ideally be explored in well-controllable and reproducible experimental animal models.

In animal models of stroke, similar to the human condition, there is a variable degree of spontaneous functional improvement after stroke, associated with a complex cascade of cellular and molecular processes that are activated within minutes after the insult, both in perilesional tissue and remote brain regions.17,18 These events include changes in genetic transcriptional and translational processes, alterations in neurotransmitter interactions, altered secretion of growth factors, gliosis, vascular remodeling, and structural changes in axons, dendrites, and synapses.19,20 Therefore, assessment of the effects of NIBS on endogenous recovery processes in animal stroke models offer excellent opportunities for the exploration of neuroplastic and neuromodulatory mechanisms, which could aid in the optimization of treatment protocols for clinical applications.

Our goal was to provide an overview of studies that assessed functional outcomes and potential mechanisms of action of rTMS and tDCS in animal models of stroke, which may guide future studies that aim to improve mechanistic insights and therapeutic utilization of NIBS effects after stroke.[…]

 

Continue —->  Noninvasive Brain Stimulation to Enhance Functional Recovery After Stroke: Studies in Animal Models – Julia Boonzaier, Geralda A. F. van Tilborg, Sebastiaan F. W. Neggers, Rick M. Dijkhuizen, 2018

 

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[WEB SITE] New technique looks inside the brain to understand more about epilepsy

Created:7 September 2018

 

Dr Simona Balestrini is about to begin a three year project using a pioneering technique to look at the activity of the brain in people with epilepsy. Here she explains what she hopes to achieve in her work with Transcranial Magnetic Stimulation (TMS) used in conjunction with electroencephalography (EEG).

We are at a very exciting time in our research into epilepsy. Genetic sequencing is beginning to generate large amounts of information with the potential to help us understand more about the causes of epilepsy and how we can best treat the condition.

When we sequence a person’s DNA, we look at the three billion letters that are packaged within almost every cell of the body. This can help to clarify whether that person’s epilepsy has a genetic contribution. But to make sense of that information, we also need to use other tools to interpret that information.

Genomics toolkit

TMS is a sophisticated tool that is part of our genomics toolkit. It is a means of looking inside a person’s brain without using needles or electrodes and can be used to interpret information gained through genetic sequencing.

TMS uses a strong magnet, similar to the one used in the MRI scanner, to induce very brief electric currents in the brain. We can measure the response of cortical circuits in the brain  to TMS and generate a direct profile of brain activity and function.

Put simply, TMS can establish a link between brain activity and different types of sensory, motor and cognitive functions. We can then establish whether a specific genetic change is impacting on the function of the brain.

How our muscles react

For some time we have been looking at the brain using TMS together with electromyogram (EMG). This allows us to measure electrical activity of muscles and their reaction time. But this technique has only allowed us to look at the motor cortex in the brain.

Now with TMS-EEG ( we are able to look at brain activity across the whole of the cortical part of the brain. It can extend the area of the brain that is being investigated, guiding and monitoring potential treatment options.

By repeating the test over a period of time, TMS can be used to show the course of epilepsy in the brain and whether different medications lead to an improvement or a decline in the condition.

Individual drug response

It is hoped that in the future TMS will be used to predict the way a person will respond to individual anti-epileptic medications. We also hope that it may help us to predict outcome in epilepsy, including the risk of SUDEP (Sudden Unexpected Death in Epilepsy).

I am really excited about this project. I feel it will help us to gain a greater understanding of the causes of epilepsy and translate clinical research into clinical care. I really hope to make a difference to the lives of the people I see in clinic every day. If we can improve seizure control for people, we can improve their quality of life.

Epilepsy Society is the best example of transformational research being translated into care for people with epilepsy.

Find out more

TMS used to measure motor cortex excitability in alternating hemiplegia.

Long-interval intracortical inhibition as biomarker for epilepsy: A transcranial magnetic stimulation study

 

Author: Nicola Swanborough

via New technique looks inside the brain to understand more about epilepsy

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[WEB SITE] What effect does transcranial magnetic stimulation have on the brain?

The procedure facilitates reorganization of connections between neurons which could be useful for therapies

Date: June 5, 2018
Source: Ruhr-University Bochum
Summary:
Researchers have gained new insights on the question of how transcranial magnetic stimulation (TMS) effects functional interconnectivity of neurons. For visualization, they employed fluorescent dyes which provide information on the activity of neurons by light. Using this technique, they showed in an animal model that TMS predisposes neuronal connections in the visual cortex of the brain for processes of reorganization.
 
FULL STORY

Researchers of the Ruhr-Universität Bochum have gained new insights on the question of how transcranial magnetic stimulation (TMS) effects functional interconnectivity of neurons. For visualisation, they employed fluorescent dyes which provide information on the activity of neurons by light. Using this technique, they showed in an animal model that TMS predisposes neuronal connections in the visual cortex of the brain for processes of reorganisation.

TMS is being used as a treatment for a number of brain diseases such as depression, Alzheimer’s disease and schizophrenia, but there has been little research on how exactly TMS works. The team of associate professor Dr Dirk Jancke of the Optical Imaging Lab in Bochum describes its new discoveries in the journal Proceedings of the National Academy of Science (PNAS).

Examining the effects on cortical maps in the visual cortex

The researchers have investigated how TMS affects the organisation of so-called orientation maps in the visual part of the brain. Those maps are partly genetically determined and partly shaped by the interaction with our surroundings. In the visual cortex, for example, neurons respond to contrast edges of certain orientations, which typically constitute boundaries of objects. Neurons that preferably respond to edges of a specific orientation are closely grouped while clusters of neurons with other orientation preferences are gradually located further away, altogether forming a systematic map across all orientations.

The team employed high frequency TMS and compared the behaviour of neurons to visual stimuli with a specific angular orientation before and after the procedure. The result: After the magnetic stimulation the neurons responded more variable, that is, their preference for a particular orientation was less pronounced than before the TMS. “You could say that after the TMS the neurons were somewhat undecided and hence, potentially open to new tasks,” explains Dirk Jancke. “Therefore, we reasoned that the treatment provides us with a time window for the induction of plastic processes during which neurons can change their functional preference.”

A short visual training remodels the maps

The team then looked into the impact of a passive visual training after TMS treatment. 20-minutes of exposure to images of a specific angular orientation led to enlargement of those areas of the brain representing the trained orientation. “Thus, the map in the visual cortex has incorporated the bias in information content of the preceding visual stimulation by changing its layout within a short time,” says Jancke. “Such a procedure — that is a targeted sensory or motor training after TMS to modify the brain’s connectivity pattern — might be a useful approach to therapeutic interventions as well as for specific forms of sensory-motor training,” explains Dirk Jancke.

Methodological challenges

Transcranial magnetic stimulation is a non-invasive painless procedure: A solenoid is being positioned above the head and the brain area in question can be activated or inhibited by means of magnetic waves. So far little is known about the impact of the procedure on a cellular network level, because the strong magnetic field of the TMS superimposes signals that are used by researchers in order to monitor the neuronal effects of the TMS. The magnetic pulse interferes in particular with electrical measurement techniques, such as EEG. In addition, other procedures used in human participants, e.g. functional magnetic resonance imaging, are too slow or their spatial resolution is too low.

Dirk Jancke’s team used voltage dependent fluorescent dyes, embedded in the membranes of the neurons, in order to measure the brain’s activity after the TMS with high spatiotemporal resolution. As soon as a neuron’s activity is modulated, the dye molecules change emission intensity. Light signals therefore provide information about immediate changes in activity of groups of neurons.

Story Source: Materials provided by Ruhr-University BochumNote: Content may be edited for style and length.


Journal Reference:

  1. Vladislav Kozyrev, Robert Staadt, Ulf T. Eysel, Dirk Jancke. TMS-induced neuronal plasticity enables targeted remodeling of visual cortical mapsProceedings of the National Academy of Sciences, 2018; 201802798 DOI: 10.1073/pnas.1802798115

 

via What effect does transcranial magnetic stimulation have on the brain? The procedure facilitates reorganization of connections between neurons which could be useful for therapies — ScienceDaily

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