EEG Concepts for Applied Neuroscience

History of EEG

  • 1875: Sir Richard Caton - electrical phenomena of cerebral hemispheres in rabbits and monkeys.
  • 1890: Sir Adolf Beck - spontaneous electrical activity of brains in rabbits and dogs.
  • 1924: Sir Hans Berger - recorded the first human EEG, termed the device as electroencephalogram.
    • An innovation in clinical neurology described as momentous.
    • Berger is known as the father of EEG.

What is EEG?

  • EEG (Electroencephalogram) is a technique for recording brain waves (electrical activity produced by the brain) using electrodes on the scalp.
  • The brain processes information through complex networks of neurons communicating via electrical signals.

EEG System Components

  • Electrodes: Small metal discs placed on the scalp to detect brain activity.
  • Amplifiers: Enhance the detected signals for analysis.
  • Analog-to-Digital Converter: Converts analog signals into digital form for computer processing.
  • Filters: High-Pass Filter (HPF), Low-Pass Filter (LPF), and Notch Filters to refine signal quality.
  • Printing and Remote Access capabilities for data management.

How EEG Works

  • Recording Process: Electrodes measure electrical signals generated by neuron activity.
  • Voltage Measurement: The electrical activity causes variations in voltage over time, which is seen as EEG waves.
  • EEG provides insights into focused attention and cognitive processing.
  • Wave Detection: Continuous monitoring allows for thousands of brain activity snapshots per second.

Understanding EEG Activity

  • Neurons are electrically charged and exchange ions, resulting in electrical signals detected by EEG electrodes.
  • EEG measures brain waves (non-linear patterns of electrical signals) to study cognitive processes and diagnose conditions.

Brain Waves Types

  • Beta Waves (14 Hz - 30 Hz): Alert state; active concentration.
  • Alpha Waves (7 Hz - 13 Hz): Relaxed state; present during calm periods and absent during intense cognition.
  • Theta Waves (4 Hz - 7 Hz): Present in young adults; linked to creativity and drowsiness.
  • Delta Waves (up to 4 Hz): Associated with deep sleep; more common in infants and during considerable brain inactivity.

Applications of EEG

  • Diagnostic Tool: Useful for diagnosing epilepsy, brain tumors, encephalopathy, and various sleep disorders.
  • Monitoring: Continuous EEG for anesthesia levels in induced comas and brain death assessments.
  • Performance Tracking: Athletes and biohackers use EEG to monitor brain activity.
  • Consumer Insight: EEG data aids in analyzing consumer responses in marketing research.
  • Academic & Quantitative Research: Insight into cognitive functions and brain interactions through research studies.

Comparison with Other Neuroimaging Techniques

  • Functional MRI (fMRI): Non-invasive; measures blood flow related to neural activity but has limitations in patients with implants or metallic items.
  • Positron Emission Tomography (PET): Visualizes brain activity via radioisotope injection but limited by short half-lives.
  • Functional Near Infrared Spectroscopy (fNIRS): Uses infrared light for brain activity but less standardized than EEG.

Advantages of EEG

  • Cost-effective relative to fMRI and PET.
  • High temporal resolution (millisecond scale).
  • Tolerant of subject movement; innovative techniques minimize artifacts.
  • Non-clinical, silent, and low-stress procedure.

Limitations of EEG

  • Limited spatial resolution; hard to localize precise brain activity.
  • Time-consuming setup with careful electrode positioning.
  • Requires sophisticated analysis due to low signal-to-noise ratio.

Neurofeedback Benefits

  • Reduces anxiety and stress; enhances learning abilities and sleep quality.
  • Improves focus and attention span; boosts memory retention.