Based on already published large evidence, non-invasive brain stimulation (NIBS) techniques like tdCS represent very important approach for the improvement of abnormal brain functions in various conditions (psychiatric and neurological). NIBS can induce temporary changes of neural oscillations and performance on various functional tasks. One of the key-points in understanding a mechanism of NIBS is the knowledge about the brains response to current stimulation and underlying brain network dynamics changes. Until recently, concurrent observation of the effect of NIBS on multiple brain networks interactions and most importantly, how current stimulation modifies these networks remained unknown because of difficulties in simultaneous recording and current stimulation. Recently, in Neuroelectrics wireless hybrid EEG/tCS 8-channel neurostimulator system has been developed that allows simultaneous EEG recording and current stimulation. Now, a relatively new imaging technique called magnetoencephalography (MEG) has emerged as a procedure that can bring new inside into brain dynamics. In this context, our group conducted a successfully proof of concept test to ensure the feasibility of concurrent MEG recording and current stimulation using Starstim and a set of non-ferrous electrodes (Figure 1). But first of all, what actually is MEG? Magnetoencephalography (MEG) is a noninvasive recording method of the magnetic flux from the head surface. Magnetic flux is associated with intracranial electrical currents produced by neural activity (the neural currents are caused by a flow of ions through postsynaptic dendritic membranes). From Maxwell equations, magnetic fields are found whenever there is a current flow, whether in a wire or a neuronal element. Hence, MEG detects these magnetic fields generated by spontaneous or evoked brain activity.
Posts Tagged magnetoencephalography
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Despite some limits on how much of the brain’s activity can be mapped at once, neuroscientists are excited. “This is remarkable,” says MEG researcher Matti Hamalainen of Massachusetts General Hospital in Boston, who wasn’t involved in the study. “MEG is moving forward conceptually into a new era.”
When neurons interact with one another, their weak electrical current generates a tiny magnetic field. To measure it with conventional MEG, scientists have people stick their heads inside a scanner like an “old-style hair dryer at a salon,” explains physicist Richard Bowtell of the University of Nottingham in the United Kingdom. Inside the scanner are superconductors, loops of ultrasensitive magnetic sensors that need to be kept extremely cold by liquid helium.
It’s an incredibly powerful technology, Bowtell says, but a person moving just 5 millimeters will ruin any attempt to read their brain activity. To study the brain during motion-related tasks, MEG researchers have devised ingenious ways to simulate movement in virtual reality.
To work around such workarounds, Bowtell’s team created a wearable 3D-printed mask that, instead of using superconductors as sensors, relies on 13 small glass cubes filled with vaporized rubidium. These optically pumped magnetometers (OPMs) get to work when a laser pulses through the vapor, lining up the atoms in its path. When neural current from the brain generates a small magnetic field, it knocks the atoms out of formation. A sensor on the other side measures fluctuations in the light from the laser to paint a map of brain activity.
Elena Boto, a physicist at the University of Nottingham, was the first to try the mask out. To compare it to a conventional scanner, she performed a series of tasks—including bending and pointing her finger, drinking from a cup, and bouncing a ball on a paddle—while using both devices. Even though her head bobbed to and fro in the mask, the brain activity recorded was practically identical to that of the fixed scanner, the researchers report today in Nature.
Some challenges remain. To counteract interference from Earth’s magnetic field, researchers had to set up two large panels with magnetic coils on either side of the mask, limiting Boto’s range of motion. Expanding the range of motion to allow for something like walking is a technically difficult chore.
But the biggest hurdle is cost. The OPM sensors, designed and manufactured by QuSpin of Louisville, Colorado, are expensive, each costing about $7000. The 13 sensors in the current mask could target only one region of the brain at a time—many dozens more would be needed to give scientists full-brain coverage. The cost of doing that, nearly $1 million, would be prohibitively expensive for many researchers, Bowtell says, though he expects the price to drop as the technology matures.
But Timothy Roberts, a neuroradiologist who works with children with autism at the Children’s Hospital of Philadelphia in Pennsylvania, says MEG masks like this one would be worth it. Neuroscientists could one day use them to track early brain development or to record brain signals in adults with movement disorders like Parkinson’s disease. Or, says Roberts, to finally get a good look at the brain activity of his often fidgety patients. “Asking a child with autism to sit still is not very easy. Asking a toddler to sit still is impossible. … I think this work is transformative.”
[ARTICLE] Effects of action observation therapy and mirror therapy after stroke on rehabilitation outcomes and neural mechanisms by MEG: study protocol for a randomized controlled trial – Full Text
Loss of upper-extremity motor function is one of the most debilitating deficits following stroke. Two promising treatment approaches, action observation therapy (AOT) and mirror therapy (MT), aim to enhance motor learning and promote neural reorganization in patients through different afferent inputs and patterns of visual feedback. Both approaches involve different patterns of motor observation, imitation, and execution but share some similar neural bases of the mirror neuron system. AOT and MT used in stroke rehabilitation may confer differential benefits and neural activities that remain to be determined. This clinical trial aims to investigate and compare treatment effects and neural activity changes of AOT and MT with those of the control intervention in patients with subacute stroke.
An estimated total of 90 patients with subacute stroke will be recruited for this study. All participants will be randomly assigned to receive AOT, MT, or control intervention for a 3-week training period (15 sessions). Outcome measurements will be taken at baseline, immediately after treatment, and at the 3-month follow-up. For the magnetoencephalography (MEG) study, we anticipate that we will recruit 12 to 15 patients per group. The primary outcome will be the Fugl-Meyer Assessment score. Secondary outcomes will include the modified Rankin Scale, the Box and Block Test, the ABILHAND questionnaire, the Questionnaire Upon Mental Imagery, the Functional Independence Measure, activity monitors, the Stroke Impact Scale version 3.0, and MEG signals.
This clinical trial will provide scientific evidence of treatment effects on motor, functional outcomes, and neural activity mechanisms after AOT and MT in patients with subacute stroke. Further application and use of AOT and MT may include telerehabilitation or home-based rehabilitation through web-based or video teaching.
Stroke is the leading cause of long-term adult disability worldwide . Most patients with stroke experience upper-extremity (UE) motor impairment  and show minimal recovery of the affected arm even 6 months after stroke . Due to the potentially severe adverse effects after stroke, it is critical in clinical practice to develop effective and specific stroke interventions to improve arm function and to explore the neural mechanisms involved [4, 5]. Action observation therapy (AOT) and mirror therapy (MT) are two examples of novel approaches concerning stroke motor recovery that are supported by neuroscientific foundations [6, 7]. However, the relative efficacy of AOT versus MT has not been validated in patients with stroke.
AOT is a promising approach grounded in basic neuroscience and the recent discovery of the mirror neuron system (MNS) . AOT commonly includes action observation and action execution and allows patients to safely practice movements and motor tasks. AOT is recommended to help patients with stroke to form accurate images of motor actions  and to mediate their motor relearning process after stroke . Researchers have found that AOT can induce stronger cognitive activity than motor imagery in patients with stroke and have suggested that AOT could be an effective approach for patients who have difficulty with motor representation . AOT is a new approach in stroke rehabilitation; therefore, only a few studies have targeted enhancement of UE motor recovery and investigated the effects of AOT in patients with stroke [8, 10, 11, 12, 13, 14]. Based on these studies, AOT has been shown to be a beneficial and effective approach to improve patient motor function. However, the heterogeneity of study designs and small sample sizes of the studies lead to no clear conclusions about the efficacy of AOT in stroke rehabilitation.
MT has emerged as another novel stroke-rehabilitation approach during the last decade [15, 16, 17]. In this treatment, participants are instructed to move their arms and watch the action reflection of the non-affected arm in the mirror, as if it were the affected one. The process creates the visual illusion of the non-affected arm as the affected arm is normally moving. MT focuses on visual and proprioceptive feedback of the non-affected limb, which may provide substitute inputs for absent or reduced proprioceptive feedback from the affected side of the body . A growing amount of academic literature has demonstrated that patients with stroke gain improvements in motor and daily function, movement control strategies, and activities of daily living [16, 17] after treatment with MT, which supports its use in stroke rehabilitation. In short, MT is potentially a simpler, less expensive, and effective stroke-rehabilitation approach for practical implementation in clinical settings.
Action observation is based on activities of the MNS and mainly involves brain areas of the inferior parietal lobe, inferior frontal gyrus, and ventral premotor cortex . Mirror neurons discharge both during the execution of motor acts or goal-directed actions and during the observation of other people performing the same or similar actions . Experimental studies in healthy adults have demonstrated that the MNS was activated during both the observation and execution of movements, which helped to form new motor patterns during action observation [21, 22, 23]. In addition, although positive effects of MT have been demonstrated in patients with stroke , there is no consensus about the underlying neural mechanisms of MT. Three hypotheses have been recently proposed to explain the beneficial effects of MT on motor recovery . Accordingly, MT may affect perceptual motor processes via three functional neural networks: (1) activation of brain regions associated with MNS [25, 26], (2) recruitment of ipsilateral motor pathways , and (3) substitution of abnormal proprioception from the affected limb with feedback from the non-affected limb [15, 18]. Few AOT and MT neurophysiological or imaging studies have been conducted in patients with stroke. No studies have directly compared and unraveled the similarities or differences in neural plastic changes between AOT and MT in these patients. It is crucial to compare neuroplasticity mechanisms between these intervention regimens to optimize rehabilitative outcomes.
The main purposes of this clinical trial are to (1) compare the immediate and retention treatment effects of AOT and MT on different outcomes with those of a dose-matched control group and (2) explore and compare the neural mechanisms and changes in cortical neural activity associated with the effects of AOT and MT in stroke patients, using magnetoencephalography (MEG).[…]
Continue —> Effects of action observation therapy and mirror therapy after stroke on rehabilitation outcomes and neural mechanisms by MEG: study protocol for a randomized controlled trial | Trials | Full Text
Researchers from the University of California San Diego and from the Veterans Affairs San Diego Healthcare System have improved neural function in a group of people with mild traumatic brain injury using low-impulse electrical stimulation to the brain, according to a study published in Brain Injury.
Although little is understood about the pathology of mild TBI, the team of researchers noted that previous work has shown that passive neuro-feedback, low-intensity pulses applied to the brain through transcranial electrical stimulation, has promise as a potential treatment.
The team’s pilot study enrolled six people with mild TBI who were experiencing post-concussion symptoms. Researchers used a form of LIP-tES combined with concurrent electroencephalography monitoring and assessed the treatment’s effect using a non-invasive functional imaging technique, magnetoencephalography, before and after treatment.
“Our previous publications have shown that MEG detection of abnormal brain slow-waves is one of the most sensitive biomarkers for mild traumatic brain injury (concussions), with about 85 percent sensitivity in detecting concussions and, essentially, no false-positives in normal patients,” senior author Dr. Roland Lee said in prepared remarks. “This makes it an ideal technique to monitor the effects of concussion treatments such as LIP-tES.”
Researchers reported that the brains in all six patients had abnormal slow-waves at the time of initial scans. After treatment, MEG scans showed reduced abnormal slow-waves and the study participants reported a significant reduction in post-concussion scores.
“For the first time, we’ve been able to document with neuroimaging the effects of LIP-tES treatment on brain functioning in mild TBI,” first author Ming-Xiong Huang added. “It’s a small study, which certainly must be expanded, but it suggests new potential for effectively speeding the healing process in mild traumatic brain injuries.”
[BLOG POST] A window into the brain networks: magnetoencephalography (MEG) and simultaneous Transcranial Current Stimulation (tCS). | Blog Neuroelectrics
Background: Providing neurofeedback (NF) of motor-related brain activity in a biologically-relevant and intuitive way could maximize the utility of a brain-computer interface (BCI) for promoting therapeutic plasticity. We present a BCI capable of providing intuitive and direct control of a video-based grasp.
Methods: Utilizing magnetoencephalography’s (MEG) high temporal and spatial resolution, we recorded sensorimotor rhythms (SMR) that were modulated by grasp or rest intentions. SMR modulation controlled the grasp aperture of a stop motion video of a human hand. The displayed hand grasp position was driven incrementally towards a closed or opened state and subjects were required to hold the targeted position for a time that was adjusted to change the task difficulty.
Results: We demonstrated that three individuals with complete hand paralysis due to spinal cord injury (SCI) were able to maintain brain-control of closing and opening a virtual hand with an average of 63 % success which was significantly above the average chance rate of 19 %. This level of performance was achieved without pre-training and less than 4 min of calibration. In addition, successful grasp targets were reached in 1.96 ± 0.15 s. Subjects performed 200 brain-controlled trials in approximately 30 min excluding breaks. Two of the three participants showed a significant improvement in SMR indicating that they had learned to change their brain activity within a single session of NF.
Conclusions: This study demonstrated the utility of a MEG-based BCI system to provide realistic, efficient, and focused NF to individuals with paralysis with the goal of using NF to induce neuroplasticity.
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[ARTICLE] Modeling the effects of noninvasive transcranial brain stimulation at the biophysical, network, and cognitive Level
Noninvasive transcranial brain stimulation (NTBS) is widely used to elucidate the contribution of different brain regions to various cognitive functions. Here we present three modeling approaches that are informed by functional or structural brain mapping or behavior profiling and discuss how these approaches advance the scientific potential of NTBS as an interventional tool in cognitive neuroscience.
(i) Leveraging the anatomical information provided by structural imaging, the electric field distribution in the brain can be modeled and simulated. Biophysical modeling approaches generate testable predictions regarding the impact of interindividual variations in cortical anatomy on the injected electric fields or the influence of the orientation of current flow on the physiological stimulation effects.
(ii) Functional brain mapping of the spatiotemporal neural dynamics during cognitive tasks can be used to construct causal network models. These models can identify spatiotemporal changes in effective connectivity during distinct cognitive states and allow for examining how effective connectivity is shaped by NTBS.
(iii) Modeling the NTBS effects based on neuroimaging can be complemented by behavior-based cognitive models that exploit variations in task performance.
For instance, NTBS-induced changes in response speed and accuracy can be explicitly modeled in a cognitive framework accounting for the speed–accuracy trade-off. This enables to dissociate between behavioral NTBS effects that emerge in the context of rapid automatic responses or in the context of slow deliberate responses. We argue that these complementary modeling approaches facilitate the use of NTBS as a means of dissecting the causal architecture of cognitive systems of the human brain.
[WEB SITE] Brain Connectivity Study Could Lead to Better Outcomes for Epilepsy Patients – Health News
The areas in purple are the regions of the brain where connectivity is significantly lower in patients with epilepsy, as compared to well patients.
The different images show the brain data from different angles. Image courtesy of Dario Englot
A new study found that patients with epilepsy have significantly weaker connections throughout their brain, particularly in regions important for attention and cognition, compared to individuals without epilepsy.
These weaker brain connections may reflect harmful long-term effects of recurrent seizures, but importantly the connectivity patterns may be used in the future to help locate which part of the brain is causing seizures, and may help doctors plan more effective surgeries.
In the study, 61 epilepsy patients and 31 controls subjects were analyzed using a non-invasive whole-brain imaging technique that detects magnetic fields produced by the electrical signals in the brain. The technique is called magnetoencephalography, and these MEG signals are used to examine the strength of connections in the brain.
Neurosurgery reisident Dario Englot, MD, PhD, sought to learn what the patterns of brain connectivity in epilepsy patients may tell us about the long-term effects of seizures on the brain. The findings suggest these connectivity patterns could help predict which individuals might benefit most from epilepsy surgery.
Intervening Earlier to Protect the Brain
The researchers found that patients who have had epilepsy for a longer period of time or have more frequent seizures had the most abnormal brain connectivity, suggesting that seizures may have progressive negative effects on the brain over time. This might advocate for early aggressive treatment of epilepsy that is not controlled with medication, to prevent these damaging effects of seizures that accumulate over time.
All patients in the study had seizures that were not controlled despite several anti-epileptic medications, and all ultimately underwent brain surgery to remove the part of the brain causing the seizures. After surgery, about two-thirds of patients became seizure-free. The investigators then examined whether brain connectivity patterns could predict which patients stopped having seizures after surgery.
More Precise Surgeries
Interestingly, those patients who became seizure-free were more likely to have an area of increased connectivity in the part of the brain causing seizures. This was not often seen in individuals who continued to have seizures after surgery. This suggests that although the brain is less connected overall in epilepsy patients, the part of the brain causing seizures may actually have increased connectivity.
Knowing this, MEG studies of brain connectivity could help determine which part of the brain is causing seizures, and may help predict a patient’s chance of becoming seizure-free after epilepsy surgery.
The study, published in the journal Brain, is the product off a multidisciplinary effort at the University of California, San Francisco, including biomedical engineer Srikantan Nagarajan, PhD, neurologist Heidi Kirsch, MD, neurosurgeon Edward Chang, M.D., and several other investigators.
University of California
Background and Objective. Mirror therapy is a new form of stroke rehabilitation that uses the mirror reflection of the unaffected hand in place of the affected hand to augment movement training. The mechanism of mirror therapy is not known but is thought to involve changes in cerebral organization. We used magnetoencephalography (MEG) to measure changes in cortical activity during mirror training after stroke. In particular, we examined movement-related changes in the power of cortical oscillations in the beta (15-30 Hz) frequency range, known to be involved in movement.
Methods. Ten stroke patients with upper limb paresis and 13 healthy controls were recorded using MEG while performing bimanual hand movements in 2 different conditions. In one, subjects looked directly at their affected hand (or dominant hand in controls), and in the other, they looked at a mirror reflection of their unaffected hand in place of their affected hand. The movement related beta desynchronization was calculated in both primary motor cortices.
Results. Movement related beta desynchronization was symmetrical during bilateral movement and unaltered by the mirror condition in controls. In the patients, movement related beta desynchronization was generally smaller than in controls, but greater in contralesional compared to ipsilesional motor cortex. This initial asymmetry in movement-related beta desynchronization between hemispheres was made more symmetrical by the presence of the mirror.
Conclusions. Mirror therapy could potentially aid stroke rehabilitation by normalizing an asymmetrical pattern of movement related beta desynchronization in primary motor cortices during bilateral movement.
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…Mirror therapy could potentially aid stroke rehabilitation by normalizing an asymmetrical pattern of movement-related beta desynchronization in primary motor cortices during bilateral movement…