A new video article in JoVE, the Journal of Visualized Experiments, describes a novel procedure to monitor brain function and aid in functional mapping of patients with diseases such as epilepsy. This procedure illustrates the use of pre-placed electrodes for cortical mapping in the brains of patients who are undergoing surgery to minimize the frequency of seizures. This technique, while invasive, provides real-time analysis of brain function at a much higher resolution than current technologies.
Typically, functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) are used in neuroimaging studies but these techniques suffer from low temporal and spatial resolution. By using electrodes implanted in the brain of an epileptic patient already undergoing treatment, scientists can now image the brain with a much higher spatial resolution, lower signal interference, and a higher temporal resolution than fMRI or EEG.
The leading author of the study, Dr. Gerwin Schalk, from the New York State Department of Health and Albany Medical College, states, “Essentially, we have created a new imaging technique. Our procedure is innovative because it is prospective, meaning, it can image brain function as it occurs. Further, it does not require an expert to derive meaningful information concerning brain function.” He also notes that it was crucial for this procedure to be demonstrated in a video format. “The procedure is a very visual process. The ancillary information such as the spatial relationships of different components, the set-up of the hospital room, and the set-up of the equipment itself cannot be represented in a typical print article. The video capacities of JoVE were an excellent vehicle to demonstrate both the general set-up and the specific implementation of the mapping system.”
…a multidisciplinary team of clinicians and scientists introduce new research applications of the electrocorticography (ECoG). The ECoG is an invasive procedure that uses strip and grid electrodes placed directly on the brain to localize seizure foci in epilepsy patients. This procedure can also be used to map cortical regions that need to be spared during resective surgery. Cortical mapping is accomplished by monitoring whether stimulation of a given electrode results in the disruption of movement or speech. Patients are typically subjected to intracranial monitoring to locate seizure foci for about a week, and this duration provides a unique window of opportunity for researchers to study the human brain in action with the ECoG, which has better signal-to-noise properties and less susceptibility to recording artifacts than the noninvasive electroencephalography (EEG).
After determining baseline activity at rest, our authors record brain activity in the high gamma frequency range, during simple cognitive, or motor tasks. Then, these investigators demonstrate how to use the SIGFRIED software system to perform rapid, real-time functional mapping based on ECoG signals, which are further analyzed to provide information regarding the brain regions associated with particular tasks.”
Watch this video WARNING – GRAPHIC MEDICAL CONTENT! This Month on JOVE – The information about the new EEG starts at 2:35!