Electrocorticography
Encyclopedia
Electrocorticography is the practice of using electrode
s placed directly on the exposed surface of the brain
to record electrical activity from the cerebral cortex
. ECoG may be performed either in the operating room during surgery (intraoperative ECoG) or outside of surgery (extraoperative ECoG). Because a craniotomy
(a surgical incision into the skull) is required to implant the electrode grid, ECoG is an invasive procedure. ECoG is currently considered to be the “gold standard” for defining epileptogenic zones in clinical practice.
and Herbert Jasper
, neurosurgeons at the Montreal Neurological Institute
. The two developed ECoG as part of their groundbreaking Montreal procedure
, a surgical protocol used to treat patients with severe epilepsy
. The cortical potentials recorded by ECoG were used to identify epileptogenic zones – regions of the cortex that generate epileptic seizure
s. These zones would then be surgically removed from the cortex during resectioning, thus destroying the brain tissue where epileptic seizures had originated. Penfield and Jasper also used electrical stimulation during ECoG recordings in patients undergoing epilepsy surgery under local anesthesia
. This procedure was used to explore the functional anatomy of the brain, mapping speech areas and identifying the somatosensory and somatomotor cortex areas to be excluded from surgical removal.
(CSF), pia mater
, and arachnoid mater
before reaching subdural recording electrodes placed just below the dura mater
(outer cranial membrane). However, to reach the scalp electrodes of an electroencephalogram (EEG), electrical signals must also be conducted through the skull
, where potentials rapidly attenuate due to the low conductivity of bone
. For this reason, the spatial resolution of ECoG is much higher than EEG, a critical imaging advantage for presurgical planning. ECoG offers a temporal resolution of approximately 5 ms and a spatial resolution of 1 cm.
Using depth electrodes, the local field potential
gives a measure of a neural population in a sphere with a radius of 0.5-3 mm around the tip of the electrode. With a sufficiently high sampling rate (more than about 10 kHz), depth electrodes can also measure action potentials. In which case the spatial resolution is down to individual neurons, and the field of view of an individual electrode is approximately 0.05-0.35 mm.
(MRI). Electrodes may either be placed outside the dura mater (epidural) or under the dura mater (subdural). ECoG electrode arrays typically consist of sixteen sterile, disposable stainless steel, carbon tip, platinum, or gold ball electrodes, each mounted on a ball and socket joint for ease in positioning. These electrodes are attached to an overlying frame in a “crown” or “halo” configuration. Subdural strip and grid electrodes are also widely used in various dimensions, having anywhere from 4 to 64 electrode contacts. The grids are transparent, flexible, and numbered at each electrode contact. Standard spacing between grid electrodes is 1 cm; individual electrodes are typically 5 mm in diameter. The electrodes sit lightly on the cortical surface, and are designed with enough flexibility to ensure that normal movements of the brain do not cause injury. A key advantage of strip and grid electrode arrays is that they may be slid underneath the dura mater into cortical regions not exposed by the craniotomy. Strip electrodes and crown arrays may be used in any combination desired. Depth electrodes may also be used to record activity from deeper structures such as the hippocampus
.
The functions most commonly mapped through DCES are primary motor, primary sensory, and language. The patient must be alert and interactive for mapping procedures, though patient involvement varies with each mapping procedure. Language mapping may involve naming, reading aloud, repetition, and oral comprehension; somatosensory mapping requires that the patient describe sensations experienced across the face and extremities as the surgeon stimulates different cortical regions.
Limitations of ECoG include:
Extraoperative ECoG
Before a patient can be identified as a candidate for resectioning surgery, MRI must be performed to demonstrate the presence of a structural lesion within the cortex, supported by EEG evidence of epileptogenic tissue. Once a lesion has been identified, ECoG may be performed to determine the location and extent of the lesion and surrounding irritative region. The scalp EEG, while a valuable diagnostic tool, lacks the precision necessary to localize the epileptogenic region. ECoG is considered to be the gold standard for assessing neuronal activity in patients with epilepsy, and is widely used for presurgical planning to guide surgical resection of the lesion and epileptogenic zone. , The success of the surgery depends on accurate localization and removal of the epileptogenic zone. ECoG data is assessed with regard to ictal spike activity – “diffuse fast wave activity” recorded during a seizure – and interictal epileptiform activity (IEA), brief bursts of neuronal activity recorded between epileptic events. ECoG is also performed following the resectioning surgery to detect any remaining epileptiform activity, and to determine the success of the surgery. Residual spikes on the ECoG, unaltered by the resection, indicate poor seizure control, and incomplete neutralization of the epileptogenic cortical zone. Additional surgery may be necessary to completely eradicate seizure activity.
Intraoperative ECoG
The objective of the resectioning surgery is to remove the epileptogenic tissue without causing unacceptable neurological consequences. In addition to identifying and localizing the extent of epileptogenic zones, ECoG used in conjunction with DCES is also a valuable tool for functional cortical mapping. It is vital to precisely localize critical brain structures, identifying which regions the surgeon must spare during resectioning (the “eloquent cortex
”) in order to preserve sensory processing, motor coordination, and speech. Functional mapping requires that the patient be able to interact with the surgeon, and thus is performed under local rather than general anesthesia. Electrical stimulation using cortical and acute depth electrodes is used to probe distinct regions of the cortex in order to identify centers of speech, somatosensory integration, and somatomotor processing. During the resectioning surgery, intraoperative ECoG may also be performed to monitor the epileptic activity of the tissue and ensure that the entire epileptogenic zone is resectioned.
Although the use of extraoperative and intraoperative ECoG in resectioning surgery has been an accepted clinical practice for several decades, recent studies have shown that the usefulness of this technique may very based on the type of epilepsy a patient exhibits. Kuruvilla and Flink reported that while intraoperative ECoG plays a critical role in tailored temporal lobectomies, in multiple subpial transections (MST), and in the removal of malformations of cortical development (MCDs), it has been found impractical in standard resection of medial temporal lobe epilepsy
(TLE) with MRI evidence of mesial temporal sclerosis (MTS). A study performed by Wennberg, Quesney, and Rasmussen demonstrated the presurgical significance of ECoG in frontal lobe epilepsy (FLE) cases.
s (BCI). BCIs are direct neural interfaces that provide control of prosthetic, electronic, or communication devices via direct use of the individual’s brain signals. Brain signals may be recorded either invasively, with recording devices implanted directly into the cortex, or noninvasively, using EEG scalp electrodes. ECoG serves to provide a partially invasive compromise between the two modalities – while ECoG does not penetrate the blood-brain barrier
like invasive recording devices, it features a higher spatial resolution and higher signal-to-noise ratio than EEG. A recent study by Shenoy et al. demonstrates the high movement classification accuracy potential of ECoG-based BCIs.
" for defining epileptogenic zones; however, this procedure is risky and highly invasive. Recent studies have explored the development of a noninvasive cortical imaging technique for presurgical planning that may provide similar information and resolution of the invasive ECoG.
In one novel approach, Bin He et al. seek to integrate the information provided by a structural MRI and scalp EEG to provide a noninvasive alternative to ECoG. This study investigated a high-resolution subspace source localization approach, FINE (first principle vectors) to image the locations and estimate the extents of current sources from the scalp EEG. A thresholding technique was applied to the resulting tomography of subspace correlation values in order to identify epileptogenic sources. This method was tested in three pediatric patients with intractable epilepsy, with encouraging clinical results. Each patient was evaluated using structural MRI, long-term video EEG monitoring with scalp electrodes, and subsequently with subdural electrodes. The ECoG data was then recorded from implanted subdural electrode grids placed directly on the surface of the cortex. MRI and computed tomography images were also obtained for each subject.
The epileptogenic zones identified from preoperative EEG data were validated by observations from postoperative ECoG data in all three patients. These preliminary results suggest that it is possible to direct surgical planning and locate epileptogenic zones noninvasively using the described imaging and integrating methods. EEG findings were further validated by the surgical outcomes of all three patients. After surgical resectioning, two patients are seizure-free and the third has experienced a significant reduction in seizures. Due to its clinical success, FINE offers a promising alternative to preoperative ECoG, providing information about both the location and extent of epileptogenic sources through a noninvasive imaging procedure.
Electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
s placed directly on the exposed surface of the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
to record electrical activity from the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
. ECoG may be performed either in the operating room during surgery (intraoperative ECoG) or outside of surgery (extraoperative ECoG). Because a craniotomy
Craniotomy
A craniotomy is a surgical operation in which a bone flap is temporarily removed from the skull to access the brain. Craniotomies are often a critical operation performed on patients recording, brain imaging, and for neurological manipulations such as electrical stimulation and chemical...
(a surgical incision into the skull) is required to implant the electrode grid, ECoG is an invasive procedure. ECoG is currently considered to be the “gold standard” for defining epileptogenic zones in clinical practice.
History
ECoG was pioneered in the early 1950s by Wilder PenfieldWilder Penfield
Wilder Graves Penfield, OM, CC, CMG, FRS was an American born Canadian neurosurgeon. During his life he was called "the greatest living Canadian"...
and Herbert Jasper
Herbert Jasper
Herbert Henri Jasper, was a Canadian psychologist, physiologist, anatomist, chemist and neurologist.Born in La Grande, Oregon, he attended Reed College in Portland, Oregon and received his PhD in psychology from the University of Iowa in 1931 and earned a Doctor of Science degree from the...
, neurosurgeons at the Montreal Neurological Institute
Montreal Neurological Institute
The Montreal Neurological Institute and Hospital is an academic medical centre dedicated to neuroscience research, training and clinical care. The Institute is part of McGill University and the Hospital is one of the five teaching hospitals of the McGill University Health Centre, in Montreal,...
. The two developed ECoG as part of their groundbreaking Montreal procedure
Montreal procedure
The Montreal procedure is a surgical procedure pioneered by Dr. Wilder Penfield of Montreal, Canada, in the 1930s. It is effective in the treatment of epilepsy....
, a surgical protocol used to treat patients with severe epilepsy
Epilepsy
Epilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
. The cortical potentials recorded by ECoG were used to identify epileptogenic zones – regions of the cortex that generate epileptic seizure
Seizure
An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
s. These zones would then be surgically removed from the cortex during resectioning, thus destroying the brain tissue where epileptic seizures had originated. Penfield and Jasper also used electrical stimulation during ECoG recordings in patients undergoing epilepsy surgery under local anesthesia
Local anesthesia
Local anesthesia is any technique to induce the absence of sensation in part of the body, generally for the aim of inducing local analgesia, that is, local insensitivity to pain, although other local senses may be affected as well. It allows patients to undergo surgical and dental procedures with...
. This procedure was used to explore the functional anatomy of the brain, mapping speech areas and identifying the somatosensory and somatomotor cortex areas to be excluded from surgical removal.
Electrophysiological basis
ECoG signals are composed of synchronized postsynaptic potentials (local field potentials), recorded directly from the exposed surface of the cortex. The potentials occur primarily in cortical pyramidal cells, and thus must be conducted through several layers of the cerebral cortex, cerebrospinal fluidCerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
(CSF), pia mater
Pia mater
Pia mater often referred to as simply the pia, is the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord. The word finds its roots in Latin, meaning literally "tender mother." The other two meningeal membranes are the dura mater and the arachnoid mater....
, and arachnoid mater
Arachnoid mater
The arachnoid mater, literally from Latin "spider -like mother", is one of the three meninges, the membranes that cover the brain and spinal cord...
before reaching subdural recording electrodes placed just below the dura mater
Dura mater
The dura mater , or dura, is the outermost of the three layers of the meninges surrounding the brain and spinal cord. It is derived from Mesoderm. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for...
(outer cranial membrane). However, to reach the scalp electrodes of an electroencephalogram (EEG), electrical signals must also be conducted through the skull
Human skull
The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...
, where potentials rapidly attenuate due to the low conductivity of bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
. For this reason, the spatial resolution of ECoG is much higher than EEG, a critical imaging advantage for presurgical planning. ECoG offers a temporal resolution of approximately 5 ms and a spatial resolution of 1 cm.
Using depth electrodes, the local field potential
Local field potential
A local field potential is a particular class of electrophysiological signals, which is dominated by the electrical current flowing from all nearby dendritic synaptic activity within a volume of tissue. A voltage is produced by the summed synaptic current flowing across the resistance of the local...
gives a measure of a neural population in a sphere with a radius of 0.5-3 mm around the tip of the electrode. With a sufficiently high sampling rate (more than about 10 kHz), depth electrodes can also measure action potentials. In which case the spatial resolution is down to individual neurons, and the field of view of an individual electrode is approximately 0.05-0.35 mm.
Procedure
The ECoG recording is performed from electrodes placed on the exposed cortex. In order to access the cortex, a surgeon must first perform a craniotomy, removing a part of the skull to expose the brain surface. This procedure may be performed either under general anesthesia or under local anesthesia if patient interaction is required for functional cortical mapping. Electrodes are then surgically implanted on the surface of the cortex, with placement guided by the results of preoperative EEG and magnetic resonance imagingMagnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(MRI). Electrodes may either be placed outside the dura mater (epidural) or under the dura mater (subdural). ECoG electrode arrays typically consist of sixteen sterile, disposable stainless steel, carbon tip, platinum, or gold ball electrodes, each mounted on a ball and socket joint for ease in positioning. These electrodes are attached to an overlying frame in a “crown” or “halo” configuration. Subdural strip and grid electrodes are also widely used in various dimensions, having anywhere from 4 to 64 electrode contacts. The grids are transparent, flexible, and numbered at each electrode contact. Standard spacing between grid electrodes is 1 cm; individual electrodes are typically 5 mm in diameter. The electrodes sit lightly on the cortical surface, and are designed with enough flexibility to ensure that normal movements of the brain do not cause injury. A key advantage of strip and grid electrode arrays is that they may be slid underneath the dura mater into cortical regions not exposed by the craniotomy. Strip electrodes and crown arrays may be used in any combination desired. Depth electrodes may also be used to record activity from deeper structures such as the hippocampus
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
.
DCES
Direct cortical electrical stimulation (DCES) is frequently performed in concurrence with ECoG recording for functional mapping of the cortex and identification of critical cortical structures. When using a crown configuration, a handheld wand bipolar stimulator may be used at any location along the electrode array. However, when using a subdural strip, stimulation must be applied between pairs of adjacent electrodes due to the nonconductive material connecting the electrodes on the grid. Electrical stimulating currents applied to the cortex are relatively low, between 2 to 4 mA for somatosensory stimulation, and near 15 mA for cognitive stimulation.The functions most commonly mapped through DCES are primary motor, primary sensory, and language. The patient must be alert and interactive for mapping procedures, though patient involvement varies with each mapping procedure. Language mapping may involve naming, reading aloud, repetition, and oral comprehension; somatosensory mapping requires that the patient describe sensations experienced across the face and extremities as the surgeon stimulates different cortical regions.
Clinical applications
Since its development in the 1950’s, ECoG has been used to localize epileptogenic zones during presurgical planning, map out cortical functions, and to predict the success of epileptic surgical resectioning. ECoG offers several advantages over alternative diagnostic modalities:- Flexible placement of recording and stimulating electrodes
- Can be performed at any stage before, during, and after a surgery
- Allows for direct electrical stimulation of the brain, identifying critical regions of the cortex to be avoided during surgery
- Greater precision and sensitivity than an EEG scalp recording - spatial resolution is higher and signal-to-noise ratio is superior due to greater proximity to neural activity
Limitations of ECoG include:
- Limited sampling time – seizures (ictalIctalIctal refers to a physiologic state or event such as a seizure, stroke or headache. The word originates from the Latin ictus, meaning a blow or a stroke...
events) may not be recorded during the ECoG recording period - Limited field of view – electrode placement is limited by the area of exposed cortex and surgery time, sampling errors may occur
- Recording is subject to the influence of anesthetics, narcotic analgesics, and the surgery itself
Intractable epilepsy
Epilepsy is currently ranked as the third most commonly diagnosed neurological disorder, afflicting approximately 2.5 million people in the United States alone. Epileptic seizures are chronic and unrelated to any immediately treatable causes, such as toxins or infectious diseases, and may vary widely based on etiology, clinical symptoms, and site of origin within the brain. For patients with intractable epilepsy – epilepsy that is unresponsive to anticonvulsants – surgical treatment may be a viable treatment option.Extraoperative ECoG
Before a patient can be identified as a candidate for resectioning surgery, MRI must be performed to demonstrate the presence of a structural lesion within the cortex, supported by EEG evidence of epileptogenic tissue. Once a lesion has been identified, ECoG may be performed to determine the location and extent of the lesion and surrounding irritative region. The scalp EEG, while a valuable diagnostic tool, lacks the precision necessary to localize the epileptogenic region. ECoG is considered to be the gold standard for assessing neuronal activity in patients with epilepsy, and is widely used for presurgical planning to guide surgical resection of the lesion and epileptogenic zone. , The success of the surgery depends on accurate localization and removal of the epileptogenic zone. ECoG data is assessed with regard to ictal spike activity – “diffuse fast wave activity” recorded during a seizure – and interictal epileptiform activity (IEA), brief bursts of neuronal activity recorded between epileptic events. ECoG is also performed following the resectioning surgery to detect any remaining epileptiform activity, and to determine the success of the surgery. Residual spikes on the ECoG, unaltered by the resection, indicate poor seizure control, and incomplete neutralization of the epileptogenic cortical zone. Additional surgery may be necessary to completely eradicate seizure activity.
Intraoperative ECoG
The objective of the resectioning surgery is to remove the epileptogenic tissue without causing unacceptable neurological consequences. In addition to identifying and localizing the extent of epileptogenic zones, ECoG used in conjunction with DCES is also a valuable tool for functional cortical mapping. It is vital to precisely localize critical brain structures, identifying which regions the surgeon must spare during resectioning (the “eloquent cortex
Eloquent cortex
Eloquent cortex is a name used by neurologists for areas of cortex that—if removed—will result in loss of sensory processing or linguistic ability, minor paralysis, or paralysis...
”) in order to preserve sensory processing, motor coordination, and speech. Functional mapping requires that the patient be able to interact with the surgeon, and thus is performed under local rather than general anesthesia. Electrical stimulation using cortical and acute depth electrodes is used to probe distinct regions of the cortex in order to identify centers of speech, somatosensory integration, and somatomotor processing. During the resectioning surgery, intraoperative ECoG may also be performed to monitor the epileptic activity of the tissue and ensure that the entire epileptogenic zone is resectioned.
Although the use of extraoperative and intraoperative ECoG in resectioning surgery has been an accepted clinical practice for several decades, recent studies have shown that the usefulness of this technique may very based on the type of epilepsy a patient exhibits. Kuruvilla and Flink reported that while intraoperative ECoG plays a critical role in tailored temporal lobectomies, in multiple subpial transections (MST), and in the removal of malformations of cortical development (MCDs), it has been found impractical in standard resection of medial temporal lobe epilepsy
Temporal lobe epilepsy
Temporal lobe epilepsy a.k.a. Psychomotor epilepsy, is a form of focal epilepsy, a chronic neurological condition characterized by recurrent seizures. Over 40 types of epilepsies are known. They fall into two main categories: partial-onset epilepsies and generalized-onset epilepsies...
(TLE) with MRI evidence of mesial temporal sclerosis (MTS). A study performed by Wennberg, Quesney, and Rasmussen demonstrated the presurgical significance of ECoG in frontal lobe epilepsy (FLE) cases.
Research applications
ECoG has recently emerged as a promising recording technique for use in brain-computer interfaceBrain-computer interface
A brain–computer interface , sometimes called a direct neural interface or a brain–machine interface , is a direct communication pathway between the brain and an external device...
s (BCI). BCIs are direct neural interfaces that provide control of prosthetic, electronic, or communication devices via direct use of the individual’s brain signals. Brain signals may be recorded either invasively, with recording devices implanted directly into the cortex, or noninvasively, using EEG scalp electrodes. ECoG serves to provide a partially invasive compromise between the two modalities – while ECoG does not penetrate the blood-brain barrier
Blood-brain barrier
The blood–brain barrier is a separation of circulating blood and the brain extracellular fluid in the central nervous system . It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion...
like invasive recording devices, it features a higher spatial resolution and higher signal-to-noise ratio than EEG. A recent study by Shenoy et al. demonstrates the high movement classification accuracy potential of ECoG-based BCIs.
Recent advances in ECoG technology
The electrocorticogram is still considered to be the "gold standardGold standard (test)
In medicine and statistics, gold standard test refers to a diagnostic test or benchmark that is the best available under reasonable conditions. It does not have to be necessarily the best possible test for the condition in absolute terms...
" for defining epileptogenic zones; however, this procedure is risky and highly invasive. Recent studies have explored the development of a noninvasive cortical imaging technique for presurgical planning that may provide similar information and resolution of the invasive ECoG.
In one novel approach, Bin He et al. seek to integrate the information provided by a structural MRI and scalp EEG to provide a noninvasive alternative to ECoG. This study investigated a high-resolution subspace source localization approach, FINE (first principle vectors) to image the locations and estimate the extents of current sources from the scalp EEG. A thresholding technique was applied to the resulting tomography of subspace correlation values in order to identify epileptogenic sources. This method was tested in three pediatric patients with intractable epilepsy, with encouraging clinical results. Each patient was evaluated using structural MRI, long-term video EEG monitoring with scalp electrodes, and subsequently with subdural electrodes. The ECoG data was then recorded from implanted subdural electrode grids placed directly on the surface of the cortex. MRI and computed tomography images were also obtained for each subject.
The epileptogenic zones identified from preoperative EEG data were validated by observations from postoperative ECoG data in all three patients. These preliminary results suggest that it is possible to direct surgical planning and locate epileptogenic zones noninvasively using the described imaging and integrating methods. EEG findings were further validated by the surgical outcomes of all three patients. After surgical resectioning, two patients are seizure-free and the third has experienced a significant reduction in seizures. Due to its clinical success, FINE offers a promising alternative to preoperative ECoG, providing information about both the location and extent of epileptogenic sources through a noninvasive imaging procedure.
See also
- Wilder PenfieldWilder PenfieldWilder Graves Penfield, OM, CC, CMG, FRS was an American born Canadian neurosurgeon. During his life he was called "the greatest living Canadian"...
- Herbert JasperHerbert JasperHerbert Henri Jasper, was a Canadian psychologist, physiologist, anatomist, chemist and neurologist.Born in La Grande, Oregon, he attended Reed College in Portland, Oregon and received his PhD in psychology from the University of Iowa in 1931 and earned a Doctor of Science degree from the...
- EpilepsyEpilepsyEpilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
- Electroencephalogram
- Magnetic Resonance ImagingMagnetic resonance imagingMagnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
- BCIBrain-computer interfaceA brain–computer interface , sometimes called a direct neural interface or a brain–machine interface , is a direct communication pathway between the brain and an external device...
- FINEIntracranial EEGIntracranial EEG is an invasive technique based on recording electroencephalography signals directly from the human cortex, as opposed to surface recordings in scalp-EEG...
- first principle vectors (combination of EEG and MRI for non-invasive alternative to intracranial EEGIntracranial EEGIntracranial EEG is an invasive technique based on recording electroencephalography signals directly from the human cortex, as opposed to surface recordings in scalp-EEG...
(icEEG))