EEG (electroencephalography) is a widely used technique for measuring brain activity by detecting electrical signals from the scalp. However, there are alternative methods that can be used instead of EEG for studying brain function.
Reactance represents the impedance from the electrical and electromagnetic fields generated from capacitors and inductors. A review of the “abnormal” EEG and an interpretation of the follow-up interictal EEG was performed. Interictal refers to the period between seizures, or convulsions characteristic of an epilepsy disorder.
fMRI
fMRI (functional magnetic resonance imaging) is a powerful imaging technique that measures changes in blood flow in the brain, which are correlated with neural activity. Unlike EEG, fMRI provides high spatial resolution, allowing researchers to pinpoint brain regions involved in specific tasks or functions. While fMRI is more expensive and less portable than EEG, it offers valuable insights into brain function.
Magnetoencephalography (MEG)
The good performance with d4 wavelet makes sense, since this wavelet does not impose the condition to be almost symmetrical and considers 4 vanishing moments characteristic of EEG waves. Besides, the bad performance observed with the Haar wavelet could be due to the non-continuous nature of the wavelet providing a poor approximation of EEG waves. Furthermore, the linear discriminant is more accurate because the contributions of the variables in the model are directly proportional to the response. An oscillograph is a device that records the waveforms of changing currents, voltages, or any other quantity that can be translated into electric energy, such as sound waves.
This category of artifacts corresponds to noise generated by the subjects themselves, whether it is voluntarily or not. In a nutshell, it is important to bear in mind that the brain is far from being the only organ that generates electromagnetic activity. In particular, the eyes and the heart produce electromagnetic activity, which shows an amplitude higher than that of the brain.
EEG can detect abnormal electrical discharges such as sharp waves, spikes, or spike-and-wave complexes that are seen in people with epilepsy; thus, it is often used to inform the medical diagnosis. EEG can detect the onset and spatio-temporal (location and time) evolution of seizures and the presence of status epilepticus. It is also used to help diagnose sleep disorders, depth of anesthesia, coma, encephalopathies, cerebral hypoxia after cardiac arrest, and brain death.
Ambulatory EEGs (aEEGs) allow for longer monitoring outside an office or a hospital setting. This test can record brain activity over several days, which increases the chances of recording during seizure activity. However, compared with inpatient video EEG monitoring, an ambulatory EEG is not as good at determining the difference between epileptic seizures and nonepileptic seizures. During the recording, a series of activation procedures may be used. These procedures may induce normal or abnormal EEG activity that might not otherwise be seen.
MEG is another non-invasive technique for measuring brain activity that detects magnetic fields produced by neuronal electrical currents. MEG has superior temporal resolution compared to fMRI and similar spatial resolution to EEG. MEG is particularly useful for studying fast neural processes such as sensory processing and motor control.
With these parameter values, the algorithm achieves an accuracy of 97.25% with a reduced number of variables (20). However, as each variable references a correlation between a decomposed level of one electrode to another, each variable involves two different electrodes. This configuration includes 40 electrodes, but if we remove the repeated electrodes that participate in more of one correlation, the number of unique electrodes is 33, nine of which belong to the motor cortex. As the proposed method generates a large number of features, which could lead to over-fitting, it is necessary to use a method to select the most important variables.
NIRS
NIRS (near-infrared spectroscopy) is a non-invasive optical imaging technique that measures changes in blood oxygen levels in the brain. While NIRS has lower spatial resolution compared to fMRI and EEG, it is portable, comfortable for participants, and suitable for studying brain activity in naturalistic settings. NIRS is commonly used in studies involving infants, children, and individuals with movement restrictions.
ECoG
ECoG (electrocorticography) involves placing electrodes directly on the surface of the brain, providing high spatial and temporal resolution of neural activity. ECoG is often used in clinical settings for mapping brain function before epilepsy surgery. While ECoG is invasive and requires surgical implantation, it offers detailed insights into brain activity not possible with EEG.
In conclusion, while EEG is a valuable tool for studying brain activity, there are alternative methods such as fMRI, MEG, NIRS, and ECoG that offer unique advantages in terms of spatial resolution, temporal resolution, comfort, and invasiveness. Researchers can choose the most appropriate technique based on their research question, study design, and participant population.
