Electrical Brain Stimulation Research Articles

Intraoperative identification of functional brain areas with RGB imaging using statistical parametric mapping: Simulation and clinical studies

Complementary technique to preoperative fMRI and electrical brain stimulation (EBS) for glioma resection could improve dramatically the surgical procedure and patient care. Intraoperative RGB optical imaging is a technique for localizing functional areas of the human cerebral cortex that can be used during neurosurgical procedures. However, it still lacks robustness to be used with neurosurgical microscopes as a clinical standard. In particular, a robust quantification of biomarkers of brain functionality is needed to assist neurosurgeons. We propose a methodology to evaluate and optimize intraoperative identification of brain functional areas by RGB imaging. This consist in a numerical 3D brain model based on Monte Carlo simulations to evaluate intraoperative optical setups for identifying functional brain areas. We also adapted fMRI Statistical Parametric Mapping technique to identify functional brain areas in RGB videos acquired for 12 patients. Simulation and experimental results were consistent and showed that the intraoperative identification of functional brain areas is possible with RGB imaging using deoxygenated hemoglobin contrast. Optical functional identifications were consistent with those provided by EBS and preoperative fMRI. We also demonstrated that a halogen lighting may be particularity adapted for functional optical imaging. We showed that an RGB camera combined with a quantitative modeling of brain hemodynamics biomarkers can evaluate in a robust way the functional areas during neurosurgery and serve as a tool of choice to complement EBS and fMRI.

Computer vision-based algorithm to sUppoRt coRrect electrode placemeNT (CURRENT) for home-based electric non-invasive brain stimulation

ObjectiveHome-based non-invasive brain stimulation (NIBS) has been suggested as an adjunct treatment strategy for neuro-psychiatric disorders. There are currently no available solutions to direct and monitor correct placement of the stimulation electrodes. To address this issue, we propose an easy-to-use digital tool to support patients for self-application. MethodsWe recruited 36 healthy participants and compared their cap placement performance with the one of a NIBS-expert investigator. We tested participants’ placement accuracy with instructions before (Pre) and after the investigator’s placement (Post), as well as participants using the support tool (CURRENT). User experience (UX) and confidence were further evaluated. ResultsPermutation tests demonstrated a smaller deviation within the CURRENT compared with Pre cap placement (p = 0.02). Subjective evaluation of ease of use and usefulness of the tool were vastly positive (8.04 out of 10). CURRENT decreased the variability of performance, ensured placement within the suggested maximum of deviation (10 mm) and supported confidence of correct placement. ConclusionsThis study supports the usability of this novel technology for correct electrode placement during self-application in home-based settings. SignificanceCURRENT provides an exciting opportunity to promote home-based, self-applied NIBS as a safe, high-frequency treatment strategy that can be well integrated in patients’ daily lives.

Case Report of Improvement in Long-COVID Symptoms in an Air Force Medic Treated With Transcranial Magnetic Stimulation Using Electro-Magnetic Brain Pulse Technique.

Long-coronavirus disease (COVID) is an ill-defined set of symptoms persisting in patients following infection with COVID-19 that range from any combination of persistent breathing difficulties to anosmia, impaired attention, memory, fatigue, or pain. Recently, noninvasive transcutaneous electrical brain stimulation techniques have been showing early signs of success in addressing some of these complaints. We postulate that the use of a stimulation technique with transcranial magnetic stimulation may also similarly be effective. A 36-year-old male suffering from symptoms of dyspnea, anosmia, and "brain fog" for 2 years following coronavirus infection was treated with 10 sessions of Electro-Magnetic Brain Pulse (EMBP®), a personalized transcranial magnetic stimulation protocol guided by the patient's electroencephalograph (EEG). At the conclusion of the treatment, the patient had improvements in mood, sense of smell, and brain fogging. Dyspnea also decreased with a gain of 11% forced expiratory volume 1/forced vital capacity. A high-sensitivity athletic training cognitive test showed an overall 27% increase in aggregate score. A significant portion of this was attributed to changes in visual clarity and decision-making speed. Post-treatment EEG showed a shift from predominantly delta waves to more synchronized alpha wave patterns during the resting state. Brain stimulation techniques appear to be showing early signs of success with long-COVID symptoms. This is the first case describing the use of a magnetic stimulation technique with quantitative test results and recorded EEG changes. Given the early success in this patient with cognition, dyspnea, and anosmia, this noninvasive treatment modality warrants further research.

Effectiveness of Transcranial Alternating Current Stimulation on Inhibitory Control and Impulsivity in Nicotine-dependent Individuals

Background Technology-based interventions, such as electrical brain stimulation may be effective in the cognitive and personality processes of substance abusers, including nicotine dependents. Objective We conducted this study to investigate the effectiveness of transcranial alternating current stimulation (tACS) using alpha frequency on inhibitory control and impulsivity in nicotine-dependent individuals. Methods We used a pre-test/post-test/follow-up quasi-experimental design with control and sham groups. We selected 30 eligible nicotine addicts from Mashhad using the available sampling method and randomly divided the subjects into three groups. We applied the intervention in eight sessions for 20 minutes in the dorsolateral prefrontal cortex for the first group, fake interventions for the second group, and no intervention for the third group. The Fagerström questionnaire, Barrett impulsivity questionnaire, and go-no-go task were used to collect data. After eight sessions, people’s inhibitory control and impulsivity were evaluated and analyzed using multivariate analysis of covariance (MANCOVA). Also, after two months, we evaluated inhibitory control data with repeated-measures analysis of variance. Results The effectiveness of alpha-tACS intervention on short- and long-term inhibitory control was significantly different in the experimental group compared to other groups (P=0.001). There was no significant difference between these three groups in impulsivity (P=0.700). Conclusion Alpha-tACS intervention effectively increases inhibitory control in nicotine-dependent individuals but does not explicitly affect their impulsivity.

Canonical Response Parameterization: Quantifying the structure of responses to single-pulse intracranial electrical brain stimulation.

Single-pulse electrical stimulation in the nervous system, often called cortico-cortical evoked potential (CCEP) measurement, is an important technique to understand how brain regions interact with one another. Voltages are measured from implanted electrodes in one brain area while stimulating another with brief current impulses separated by several seconds. Historically, researchers have tried to understand the significance of evoked voltage polyphasic deflections by visual inspection, but no general-purpose tool has emerged to understand their shapes or describe them mathematically. We describe and illustrate a new technique to parameterize brain stimulation data, where voltage response traces are projected into one another using a semi-normalized dot product. The length of timepoints from stimulation included in the dot product is varied to obtain a temporal profile of structural significance, and the peak of the profile uniquely identifies the duration of the response. Using linear kernel PCA, a canonical response shape is obtained over this duration, and then single-trial traces are parameterized as a projection of this canonical shape with a residual term. Such parameterization allows for dissimilar trace shapes from different brain areas to be directly compared by quantifying cross-projection magnitudes, response duration, canonical shape projection amplitudes, signal-to-noise ratios, explained variance, and statistical significance. Artifactual trials are automatically identified by outliers in sub-distributions of cross-projection magnitude, and rejected. This technique, which we call "Canonical Response Parameterization" (CRP) dramatically simplifies the study of CCEP shapes, and may also be applied in a wide range of other settings involving event-triggered data.

Insights into Advanced Neurological Dysfunction Mechanisms Following DBS Surgery in Parkinson's Patients: Neuroinflammation and Pyroptosis.

Parkinson's disease is a severe neurodegenerative disorder. Currently, deep brain electrical stimulation (DBS) is the first line of surgical treatment. However, serious neurological impairments such as speech disorders, disturbances of consciousness, and depression after surgery limit the efficacy of treatment. In this review, we summarize the recent experimental and clinical studies that have explored the possible causes of neurological deficits after DBS. Furthermore, we tried to identify clues from oxidative stress and pathological changes in patients that could lead to the activation of microglia and astrocytes in DBS surgical injury. Notably, reliable evidence supports the idea that neuroinflammation is caused by microglia and astrocytes, which may contribute to caspase-1 pathway-mediated neuronal pyroptosis. Finally, existing drugs and treatments may partially ameliorate the loss of neurological function in patients following DBS surgery by exerting neuroprotective effects.

Electrical Stimulation of Temporal and Limbic Circuitry Produces Distinct Responses in Human Ventral Temporal Cortex.

The human ventral temporal cortex (VTC) is highly connected to integrate visual perceptual inputs with feedback from cognitive and emotional networks. In this study, we used electrical brain stimulation to understand how different inputs from multiple brain regions drive unique electrophysiological responses in the VTC. We recorded intracranial EEG data in 5 patients (3 female) implanted with intracranial electrodes for epilepsy surgery evaluation. Pairs of electrodes were stimulated with single-pulse electrical stimulation, and corticocortical evoked potential responses were measured at electrodes in the collateral sulcus and lateral occipitotemporal sulcus of the VTC. Using a novel unsupervised machine learning method, we uncovered 2-4 distinct response shapes, termed basis profile curves (BPCs), at each measurement electrode in the 11-500 ms after stimulation interval. Corticocortical evoked potentials of unique shape and high amplitude were elicited following stimulation of several regions and classified into a set of four consensus BPCs across subjects. One of the consensus BPCs was primarily elicited by stimulation of the hippocampus; another by stimulation of the amygdala; a third by stimulation of lateral cortical sites, such as the middle temporal gyrus; and the final one by stimulation of multiple distributed sites. Stimulation also produced sustained high-frequency power decreases and low-frequency power increases that spanned multiple BPC categories. Characterizing distinct shapes in stimulation responses provides a novel description of connectivity to the VTC and reveals significant differences in input from cortical and limbic structures.SIGNIFICANCE STATEMENT Disentangling the numerous input influences on highly connected areas in the brain is a critical step toward understanding how brain networks work together to coordinate human behavior. Single-pulse electrical stimulation is an effective tool to accomplish this goal because the shapes and amplitudes of signals recorded from electrodes are informative of the synaptic physiology of the stimulation-driven inputs. We focused on targets in the ventral temporal cortex, an area strongly implicated in visual object perception. By using a data-driven clustering algorithm, we identified anatomic regions with distinct input connectivity profiles to the ventral temporal cortex. Examining high-frequency power changes revealed possible modulation of excitability at the recording site induced by electrical stimulation of connected regions.

Focused Epicranial Brain Stimulation by Spatial Sculpting of Pulsed Electric Fields Using High Density Electrode Arrays.

Transcranial electrical neuromodulation of the central nervous system is used as a non-invasive method to induce neural and behavioral responses, yet targeted non-invasive electrical stimulation of the brain with high spatial resolution remains elusive. This work demonstrates a focused, steerable, high-density epicranial current stimulation (HD-ECS) approach to evoke neural activity. Custom-designed high-density (HD) flexible surface electrode arrays are employed to apply high-resolution pulsed electric currents through skull to achieve localized stimulation of the intact mouse brain. The stimulation pattern is steered in real time without physical movement of the electrodes. Steerability and focality are validated at the behavioral, physiological, and cellular levels using motor evoked potentials (MEPs), intracortical recording, and c-fos immunostaining. Whisker movement is also demonstrated to further corroborate the selectivity and steerability. Safety characterization confirmed no significant tissue damage following repetitive stimulation. This method can be used to design novel therapeutics and implement next-generation brain interfaces.

Visual networks: Electric brain stimulation and diffusion tensor imaging

ObjectiveThe present study investigated the networks of visual functional areas using electric brain stimulation (EBS) and diffusion tensor imaging (DTI). MethodsThirteen patients with intractable focal epilepsy in which visual functional areas were identified by EBS were enrolled. An electric stimulation at 50Hz was applied to electrodes during several tasks. DTI was used to identify subcortical fibers originating from the visual functional areas identified by EBS. ResultThe electrical stimulation induced three types of visual symptoms: visual illusions (change of vision), visual hallucinations (appearance of a new object), and blurred vision. Visual illusions were associated with stimulation of lateral temporo-parieto-occipital areas, and visual hallucinations with stimulation of lateral/basal temporal areas, the occipital lobe and the precuneus. Stimulus intensities eliciting visual illusions were significantly higher than those for visual hallucinations. Tractography revealed that the superior fronto-occipital fasciculus was associated with visual illusions and the middle longitudinal fasciculus with visual hallucinations, and both symptoms shared several subcortical fibers such as the vertical occipital fasciculus, inferior fronto-occipital fasciculus, superior longitudinal fasciculus, inferior longitudinal fasciculus, optic radiations, and commissural fibers. ConclusionThe present study revealed the characteristic cortical regions and networks of visual functional areas. The results obtained provide information on human visual functions and are a practical guide for electrical cortical stimulation.

The origin of pleasant sensations: Insight from direct electrical brain stimulation

Research into the neuroanatomical basis of emotions has resulted in a plethora of studies over the last twenty years. However, studies about positive emotions and pleasant sensations remain rare and their anatomical-functional bases are less understood than that of negative emotions. Pleasant sensations can be evoked by electrical brain stimulations (EBS) during stereotactic electroencephalography (SEEG) performed for pre-surgical exploration in patients with drug-resistant epilepsy. We conducted a retrospective analysis of 10 106 EBS performed in 329 patients implanted with SEEG in our epileptology department. We found that 13 EBS in 9 different patients evoked pleasant sensations (.60% of all responses). By contrast we collected 111 emotional responses of negative valence (i.e., 5.13% of all responses). EBS evoking pleasant sensations were applied at 50 Hz with an average intensity of 1.4 ± .55 mA (range .5–2 mA). Pleasant sensations were reported by nine patients of which three patients presented responses to several EBS. We found a male predominance among the patients reporting pleasant sensations and a prominent role of the right cerebral hemisphere. Results show the preponderant role of the dorsal anterior insula and amygdala in the occurrence of pleasant sensations.

Bibliometric Analysis of the Published Studies on the Kindling Model between 1980 and 2023

Objective: Kindling is an animal model of epilepsy induced by electrical stimulation of the brain. The present study aimed to present a different perspective with a bibliometric approach by using the literature data on the “Kindling model” related keywords in the Web of Science (WoS) online database between 1980 and 2023.
 Methods: The bibliometric data were obtained from the online database WoS and analyzed and visualized with the VoS Viewer Program. The bibliometric datasets were analyzed and visualized regarding article productivity numbers according to years, article productivity numbers according to countries, the most used keywords according to authors, and cross-country cooperation.
 Result: Considering the results of the analysis of the published datasets, 2022 was determined as the year with the highest article productivity, and an acceleration was observed in the publication increase rate on the subject in general. When the order of the countries in the top three in the number of article productivity was examined, the USA, Germany, and Japan are the main countries, respectively. The most used keywords by the authors were determined as “Epilepsy”, “Kindling”, and “Hippocampus”. In the cooperation among countries, it was found that the USA, Germany, and Japan had more cooperation with other countries, respectively.
 Conclusıon: This study will contribute to the literature by providing a detailed understanding of the research basis, relevant research results, current research boundaries and main research focus in the Kindling Model.

A charge analysis of non-invasive electrical brain stimulation

The brain is an electric organ. As such, for well over a hundred years, physicists, engineers, biologists, and physicians have used electromagnetic theory to try to understand how the brain works and to diagnose and treat disease. The field of electro-neuroscience is immense with thousands of papers being published each year. In this paper, we provide physics students with an introduction to the field using a conventional model of the head that employs four concentric spheres having different conductivities to represent the scalp, skull, cerebrospinal fluid (CSF), and the brain itself. To ground the discussion, we use the specific case of non-invasive DC electrical stimulation of the brain through electrodes applied to the surface of the scalp, a procedure known as transcranial DC stimulation or tDCS. Currently, tDCS is under clinical investigation for such diseases as depression, anxiety, and chronic pain as well as to enhance the performance of athletes and the training of fighter pilots. We solve the corresponding physics problem from a charge perspective and explain why the charge distributions look the way they do using what we call the “sensing pixel” technique. This paper can introduce students to the ways in which electromagnetic theory is being applied to problems in neuroscience; in this case, the problem of how to non-invasively stimulate the brain to treat disease or improve performance.

Termination of seizures by ictal transcranial focal cortex stimulation.

Whereas high-level evidence exists on chronic neuromodulatory effects of different brain stimulation approaches in reducing seizure frequency, evidence for acute antiseizure effects of electrical brain stimulation during seizures is sparse. As part of an ongoing trial, we implanted a patient with a novel focal cortex stimulation (FCS) device with a Laplacian electrode placed over a precentral focal cortical dysplasia. The baseline seizure frequency was 125 per month, consisting of (i) focal aware sensory seizures that invariably progressed to uni- or bilateral tonic contraction and clonic jerking, and (ii) primary motor seizures. Besides an overall reduction in seizure frequency, on-demand stimulation had an immediate effect on seizures with a sensory phase, whereby 63%-86% of these seizures were terminated by ictal stimulation. These observations provide the first evidence that ictal self-triggered transcranial focal cortex stimulation can significantly interfere with the progression of seizure semiology.

Neuromodulation Based on Brain-computer Interface Technology

Therapeutic brain-computer interface (BCI) is a fast-developing area with considerable potential in improving the life qualities of various patients. Although a complete mechanistic understanding is yet achieved, empirical explorations into neuromodulatory devices, including deep brain stimulation (DBS), transcranial magnetic and electrical stimulation (TMS, TES), and electroencephalography (EEG), have enriched the repertoire for treating many neurologic diseases. Four such diseases discussed are Parkinson's disease (PD), substance use disorder (SUD), epilepsy, and depression. BCI devices alleviate symptoms by modulating neuronal activities, for instance, via directly delivering electrical stimulation, but each disease poses challenges now. Currently, neuromodulation techniques for PD and epilepsy are relatively mature and require few more perfections, while the ones concerning SUD and depression are young and fledgling, but multiple studies have revealed preliminary success and therapeutic potential. This article aims to review four techniques’ applications in four common neurologic disorders, including current achievements, associated difficulties, and potential future directions.

Non-Invasive Electric and Magnetic Brain Stimulation for the Treatment of Fibromyalgia.

Although fibromyalgia is defined by its core muscular nociceptive component, it also includes multiple dysfunctions that involve the musculoskeletal, gastrointestinal, immune, endocrine, as well as the central and peripheral nervous systems, amongst others. The pathogenic involvement of the nervous system and the numerous neurological and neuroinflammatory symptoms of this disease may benefit from neuromodulatory stimulation techniques that have been shown to be effective and safe in diverse nervous system pathologies. In this systematic review, we outline current evidence showing the potential of non-invasive brain stimulation techniques, such as therapeutic strategies in fibromyalgia. In addition, we evaluate the contribution of these tools to the exploration of the neurophysiological characteristics of fibromyalgia. Considering that the pathogenesis of this disease is unknown, these approaches do not aim to causally treat this syndrome, but to significantly reduce a range of key symptoms and thus improve the quality of life of the patients.

Paradoxical kinesia may no longer be a paradox waiting for 100 years to be unraveled.

Parkinson's disease (PD) is a progressive neurodegenerative disorder mainly characterized by bradykinesia and akinesia. Interestingly, these motor disabilities can depend on the patient emotional state. Disabled PD patients remain able to produce normal motor responses in the context of urgent or externally driven situations or even when exposed to appetitive cues such asmusic. To describe this phenomenon Souques coined theterm "paradoxical kinesia" a century ago. Since then, the mechanisms underlying paradoxical kinesia are still unknown due to a paucity of valid animal models that replicate this phenomenon. To overcome this limitation, we established two animal models of paradoxical kinesia. Using these models, we investigated the neural mechanisms of paradoxical kinesia, with the results pointing tothe inferior colliculus (IC) as a key structure. Intracollicular electrical deep brain stimulation, glutamatergic and GABAergic mechanisms may be involved in the elaboration of paradoxical kinesia. Since paradoxical kinesia might work by activation of some alternative pathway bypassing basal ganglia, we suggest the IC as a candidate to be part of this pathway.

The Comparable Effect of tDCS and Core Exercises on Balance and Mobility in Patients With Multiple Sclerosis

Objectives: As a major feature of the disease, motor-related complications, including loss of balance and reduced ability to walk were seen in multiple sclerosis (MS). The purpose of this study was to investigate the effect of core stability exercises and transcranial direct-current stimulation (tDCS) as a non-invasive brain stimulation on balance, walking capacity, and quality of life in patients with MS. Methods: In this randomized clinical trial study with a pretest-posttest design, 29 female patients with an Expanded Disability Status Scale (EDSS) of less than 4.5 (3.75±1.31) and a mean age of 38.36±7.99 years were purposefully selected from patients referring to MS society of Tehran during 2021 and then randomly assigned to the following three groups: core stability exercises, anodal tDCS, and sham. Variables, such as balance, walking capacity, and quality of life were measured before and after the interventions. Subjects in the core stability training group participated in core stability exercises for three weeks, and subjects in both sham and anodal tDCS groups received direct brain electrical stimulation for five sessions. Results: A significant improvement in balance and walking capacity were seen both in the anodal tDCS and the core stability training groups (P<0.05). Moreover, mobility was significantly changed in the tDCS group (P<0.05). However, no significant difference in the quality of life was seen between the groups. Discussion: Our findings indicate comparable effects of tDCS, and core stability training on balance and walking capacity in patients with MS. Therefore, in addition to exercises, tDCS can be considered a promising tool for the neurorehabilitation of patients with MS.

Post-electroconvulsive therapy cognitive alterations

Introductionectroconvulsive therapy (ECT) is a medical treatment most often used for patients with severe major depression or bipolar disorder who have not responded to other treatments, as well as for resistant schizophrenia, and consists of brief electrical stimulation of the brain while the patient is under anesthesia. It is usually administered by a team of trained health care professionals, including a psychiatrist, an anesthesiologist and a nurse or physician assistant.The mode of action is not well known, but it is assumed that ECT is associated with a significant reduction in brain connections in the dorsolateral prefrontal cortex, which is associated with a significant decrease in depressive symptoms. This would support the hypothesis that hyper-connectivity in this area of the brain is closely linked to depression.Despite its great effectiveness, this technique remains limited by numerous contraindications and exposes the patient to a multitude of short-, medium- and long-term side effects, notably cognitive disorders.ObjectivesTo shed light on the cognitive disorders affecting mnesic processes, learning and thinking after electroconvulsive therapy.MethodsWe have performed a systematic literature review using the following keywords on the GoogleScholar database: cognitive impairment post electroconvulsive therapy, cognitive effects of electroconvulsive therapy, electroconvulsive side effects, ECT.ResultsMost of the studies on cognitive disorders after ECT have focused on mnesic abilities, in particular the deterioration of anterograde memory which is at its maximum just after the session and which recovers progressively and spontaneously. The deterioration of retrograde memory, on the other hand, depends on the administered dose, the type and the location of the electrodes, and has a greater tendency to affect recent memories than old ones.Other studies have focused on the speed of the process of information, which is also affected, with a significant decrease, especially in depressed people, a decrease that can be progressively resolved with time. Concerning attentiveness, some studies have noted a minimal decrease, especially in the lateral visual fields, and a perseveration in verbal expression. These studies also noted a deterioration of executive functions with a decrease in performance on the STROOP and MTM tests and also in verbal fluency.ConclusionsThe occurrence and preservation of cognitive deficits after ECT is a much debated subject with many controversial studies, and despite the numerous studies on this subject, we are still far from conclusive and exploitable results, especially with the intricacy of the diversity of parameters, materials and techniques of ECT, and also because of other factors such as individual peculiarities, neurological co-morbidities, and polymedication to psychotropic drugs.Disclosure of InterestNone Declared

Multielectrode Cortical Stimulation Selectively Induces Unidirectional Wave Propagation of Excitatory Neuronal Activity in Biophysical Neural Model.

Cortical stimulation is emerging as an experimental tool in basic research and a promising therapy for a range of neuropsychiatric conditions. As multielectrode arrays enter clinical practice, the possibility of using spatiotemporal patterns of electrical stimulation to induce desired physiological patterns has become theoretically possible, but in practice can only be implemented by trial-and-error because of a lack of predictive models. Experimental evidence increasingly establishes traveling waves as fundamental to cortical information-processing, but we lack an understanding of how to control wave properties despite rapidly improving technologies. This study uses a hybrid biophysical-anatomical and neural-computational model to predict and understand how a simple pattern of cortical surface stimulation could induce directional traveling waves via asymmetric activation of inhibitory interneurons. We found that pyramidal cells and basket cells are highly activated by the anodal electrode and minimally activated by the cathodal electrodes, while Martinotti cells are moderately activated by both electrodes but exhibit a slight preference for cathodal stimulation. Network model simulations found that this asymmetrical activation results in a traveling wave in superficial excitatory cells that propagates unidirectionally away from the electrode array. Our study reveals how asymmetric electrical stimulation can easily facilitate traveling waves by relying on two distinct types of inhibitory interneuron activity to shape and sustain the spatiotemporal dynamics of endogenous local circuit mechanisms.SIGNIFICANCE STATEMENT Electrical brain stimulation is becoming increasingly useful to probe the workings of brain and to treat a variety of neuropsychiatric disorders. However, stimulation is currently performed in a trial-and-error fashion as there are no methods to predict how different electrode arrangements and stimulation paradigms will affect brain functioning. In this study, we demonstrate a hybrid modeling approach, which makes experimentally testable predictions that bridge the gap between the microscale effects of multielectrode stimulation and the resultant circuit dynamics at the mesoscale. Our results show how custom stimulation paradigms can induce predictable, persistent changes in brain activity, which has the potential to restore normal brain function and become a powerful therapy for neurological and psychiatric conditions.

A new full closed-loop brain-machine interface approach based on neural activity: A study based on modeling and experimental studies

BackgroundThe bidirectional brain-machine interfaces algorithms are machines that decode neural response in order to control the external device and encode position of artificial limb to proper electrical stimulation, so that the interface between brain and machine closes. Most BMI researchers typically consider four basic elements: recording technology to extract brain activity, decoding algorithm to translate brain activity to the predicted movement of the external device, external device (prosthetic limb such as a robotic arm), and encoding interface to convert the motion of the external machine to set of the electrical stimulation of the brain. New methodIn this paper, we develop a novel approach for bidirectional brain-machine interface (BMI). First, we propose a neural network model for sensory cortex (S1) connected to the neural network model of motor cortex (M1) considering the topographic mapping between S1 and M1. We use 4-box model in S1 and 4-box in M1 so that each box contains 500 neurons. Individual boxes include inhibitory and excitatory neurons and synapses. Next, we develop a new BMI algorithm based on neural activity. The main concept of this BMI algorithm is to close the loop between brain and mechaical external device. ResultsThe sensory interface as encoding algorithm convert the location of the external device (artificial limb) into the electrical stimulation which excite the S1 model. The motor interface as decoding algorithm convert neural recordings from the M1 model into a force which causes the movement of the external device. We present the simulation results for the on line BMI which means that there is a real time information exchange between 9 boxes and 4 boxes of S1-M1 network model and the external device. Also, off line information exchange between brain of five anesthetized rats and externnal device was performed. The proposed BMI algorithm has succeeded in controlling the movement of the mechanical arm towards the target area on simulation and experimental data, so that the BMI algorithm shows acceptable WTPE and the average number of iterations of the algorithm in reaching artificial limb to the target region.Comparison with existing methods and Conclusions: In order to confirm the simulation results the 9-box model of S1-M1 network was developed and the valid “spike train” algorithm, which has good results on real data, is used to compare the performance accuracy of the proposed BMI algorithm versus “spike train” algorithm on simulation and off line experimental data of anesthetized rats. Quantitative and qualitative results confirm the proper performance of the proposed algorithm compared to algorithm “spike train” on simulations and experimental data.