EEG Applications

Electroencephalography (EEG)

Electroencephalography (EEG) is a non-invasive method widely used in research for recording the electrical activity of the brain. It is a valuable tool in research for its ability to capture real-time brain activity, offering insights into the neural basis of cognitive and behavioral processes and aiding in the development of neurotechnological applications.

Delta Waves (δ): 0.5 to 3 Hz
  • These are the slowest brain waves and are found in deep sleep and in very deep, meditative states. They also occur in serious brain disorders.
Theta Waves (θ): 4 to 7 Hz
  • Theta waves are typically associated with drowsiness, early stages of sleep, and dreaming. They are also linked to creative insights, deep meditation, and access to the subconscious.
Alpha Waves (α): 8 to 12 Hz
  • Present in a relaxed state, especially with closed eyes. Alpha waves are linked to a state of relaxed alertness and are prominent during meditation and calm focus.
Beta Waves (β): 13 to 30 Hz
  • These waves are associated with normal waking consciousness. They are present during focus, concentration, active thinking, and anxiety.
Gamma Waves (γ): 30 Hz and above
  • Gamma waves are associated with high-level cognitive functioning, problem-solving, and conscious perception. They are also linked to states of heightened awareness and can be a sign of active learning.

Electroencephalography (EEG) measures electrical activity in the brain and is often analyzed in terms of different frequency bands, each associated with various brain states and activities. The primary EEG frequency bands are:

Image credit to: https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/brain-waves

Each band reflects different aspects of brain activity and state of consciousness. EEG recordings can be analyzed to understand various brain disorders, sleep patterns, levels of alertness, and other cognitive functions.


Historical Background:
  • EEG was first developed in the early 20th century. Hans Berger, a German psychiatrist, recorded the first human EEG in 1924 and published his findings in 1929, demonstrating the existence of electrical activity in the human brain.
Temporal Resolution:
  • EEG's strength lies in its temporal resolution. It can measure brain activity in milliseconds (ms), which is significantly faster than other neuroimaging techniques like fMRI (Functional Magnetic Resonance Imaging) that have a temporal resolution in seconds.
Spatial Resolution:
  • The spatial resolution of EEG is limited compared to other techniques. While fMRI can provide spatial resolution in the order of a few millimeters, EEG's spatial resolution is in the range of centimeters.
Frequency Bands:
  • EEG signals are categorized into different frequency bands: Delta (<4 Hz), Theta (4-7 Hz), Alpha (8-12 Hz), Beta (13-30 Hz), and Gamma (>30 Hz). These bands are associated with different states of brain activity, like sleep, relaxation, and cognitive processing.
Event-Related Potentials (ERPs):
  • ERPs are specific brain responses to stimuli measured by EEG. The P300 wave, for instance, is a positive deflection in voltage occurring approximately 300 milliseconds after stimulus onset, often used in cognitive research.
Brain-Computer Interfaces (BCIs):
  • In BCI research, EEG has been instrumental. For example, a study published in "Frontiers in Neuroscience" (2018) demonstrated the use of EEG-based BCIs in improving communication for patients with locked-in syndrome.
Neurofeedback:
  • Neurofeedback uses real-time EEG data to train individuals to modulate their brain activity. Studies, like one published in "Applied Psychophysiology and Biofeedback" (2019), have shown its effectiveness in treating conditions like ADHD and anxiety.
Sleep Research:
  • EEG is the gold standard for sleep stage classification. For instance, delta waves are prevalent in deep sleep, while REM sleep shows patterns similar to wakefulness.
Clinical Applications:
  • Clinically, EEG is essential for diagnosing epilepsy. A study in "Epilepsia" (2017) highlighted its role in identifying seizure types and guiding treatment plans.
Limitations and Advances:
  • While traditional EEG has limitations in spatial resolution, advancements like high-density EEG (with more electrodes) are improving this aspect. Research in "NeuroImage" (2020) showcased the enhanced spatial resolution of high-density EEG.

It's important for researchers and practitioners to be aware of the regulatory status of these EEG devices and adhere to the guidelines for their intended use, especially in the United States where the FDA regulates medical devices. This ensures that the devices are used ethically and safely within the bounds of current regulations.

Research Use Only: Researchers should use these devices with the understanding that they are for research purposes only, and not for clinical or diagnostic applications unless they have received FDA clearance or approval for such uses.

Ethical and Safety Considerations: Research involving EEG device should adhere to stringent ethical and safety guidelines. This includes obtaining necessary institutional review board (IRB) approvals and ensuring informed consent from all research participants, with clear communication about the investigational nature of the device.

Items marked with* are investigational devices and for research use only. CAUTION - Investigational Device. Limited by Federal (or United States) law to investigational use.