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BASICS OF EEG AND FUNDAMENTALS OF
IT’S MEASUREMENT
Timeline of EEG invention
1875
• Richard Caton - Presence of continuous and
spontaneous electrical activity from the brain surface
of rabbits and monkeys
1890
• Adolf Beck – Sensory stimulus can induce spontaneous
and rhythmic oscillation
1912
• Vladimir Pravdich Neminsky – Produced first animal
EEG and evoked potential of mammalian dog
1924
• Hans Berger - Recorded the first human EEG
Figure: Hans Berger and his invention
Cerebral generators of EEG potentials
Figure: Neuronal structure Figure: Neuron – Neuron connection
Electrical signal propagation
Figure: Signal transmission Figure: Signal transmission
Figure: Pyramidal cell’s alignment
Figure: Single pyramidal cell
EEG Recording
Figure: Schematic diagram of a modern EEG Machine from the
subject to the data retrieved
Figure: Illustration of EEG electrodes and signal
Figure: 10/20 System of EEG electrode placement
• Nasion
• Inion
• Left and right
auricular points
Figure: EEG Scalp electrodes
EEG Electrode Placement
Filters
Figure: Low frequency Filter Figure: Low frequency Filter characteristics
Figure: High Frequency Filter Figure: High Frequency Filter Characteristics
Figure : 60 Hz notch filter Figure : 60 Hz notch filter characteristics
Amplifier
• All EEG amplifiers are differential amplifiers.
• Differential amplifier takes two input
voltages and produces an output that is an
amplified version of the difference between
the two inputs
• Advantage – Cancels out the external noise
Rules of Polarity on EEG
 If input 1 is negative with respect to input 2, there is an
upward deflection
 If input 1 is positive with respect to input 2, there is a
downward deflection
 An upward deflection is surface negative, and a
downward deflection is surface positive
 When there is no deflection, the inputs are equipotential
and are either equally active or inactive
Equipotential
Polarity Convention - Example
Montage
Logical and orderly arrangement of channels/electrode pairs on the display
• Bipolar Montage
• Common electrode reference montage
• Average reference montage
• Laplacian montage
Figure : Commonly used bipolar longitudinal
pattern (Double Banana)
Figure : EEG of Bipolar montage
Figure: Referential montage Figure: Laplacian montage
Figure: Normal EEG in awake state
EEG Artifacts
• Artifacts are unwanted noise signals in an EEG record.
• Classification of artefacts is based on the source of generation:
Physiological artifacts and external artifacts.
• Physiologic artifacts:
• Any minor body movements
• EMG
• ECG
• Eye movements etc.
• Non Physiologic artifacts:
• Damage of electrodes
• Cable movements
• Broken wire contacts
• Impedance fluctuation
• 60/50 H artifact etc
Figure: EEG Artifacts
Advantages & Applications of EEG
• Excellent temporal resolution
• EEG can determine the relative strengths and positions of electrical activity in different brain regions.
• EEG does not involve exposure to high intensity magnetic field
• Relatively cheap and simple to operate
• Applications of the EEG in humans and animals involve:
 Research
 Clinics
 Clinical application- EEG is one of the main diagnostic tests for epilepsy
Normal EEG compared to EEG including a seizure: (A) Normal EEG of 15 seconds; (B) EEG
of the same patient having an epileptic seizure visible on electrodes P8 and T8.
Clinical applications
• Monitor alertness, coma and brain death
• Locate areas of damage following head injury, stroke, tumor.
• Monitor cognitive engagement (alpha rhythm)
• Control anesthesia depth
• Investigate epilepsy and locate seizure origin
• Investigate sleep disorder and physiology.
• Etc.
References
• Teplan, M. (2002). FUNDAMENTALS OF EEG MEASUREMENT.
• Britton JW, Frey LC, Hopp JLet al., authors; St. Louis EK, Frey LC, editors. Electroencephalography (EEG):
An Introductory Text and Atlas of Normal and Abnormal Findings in Adults, Children, and Infants [Internet].
Chicago: American Epilepsy Society; 2016. Available from:
https://www.ncbi.nlm.nih.gov/books/NBK390354/
• https://doi.org/10.1684/epd.2020.1217
• Light, G. A., Williams, L. E., Minow, F., Sprock, J., Rissling, A., Sharp, R., Swerdlow, N. R., & Braff, D. L.
(2010). Electroencephalography (EEG) and event-related potentials (ERPs) with human participants. Current
protocols in neuroscience, Chapter 6, Unit–6.25.24. https://doi.org/10.1002/0471142301.ns0625s52
Thankyou…

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1 basics of eeg and fundamentals of its measurement

  • 1. BASICS OF EEG AND FUNDAMENTALS OF IT’S MEASUREMENT
  • 2. Timeline of EEG invention 1875 • Richard Caton - Presence of continuous and spontaneous electrical activity from the brain surface of rabbits and monkeys 1890 • Adolf Beck – Sensory stimulus can induce spontaneous and rhythmic oscillation 1912 • Vladimir Pravdich Neminsky – Produced first animal EEG and evoked potential of mammalian dog 1924 • Hans Berger - Recorded the first human EEG Figure: Hans Berger and his invention
  • 3. Cerebral generators of EEG potentials Figure: Neuronal structure Figure: Neuron – Neuron connection
  • 4. Electrical signal propagation Figure: Signal transmission Figure: Signal transmission
  • 5. Figure: Pyramidal cell’s alignment Figure: Single pyramidal cell
  • 6. EEG Recording Figure: Schematic diagram of a modern EEG Machine from the subject to the data retrieved Figure: Illustration of EEG electrodes and signal
  • 7. Figure: 10/20 System of EEG electrode placement • Nasion • Inion • Left and right auricular points Figure: EEG Scalp electrodes EEG Electrode Placement
  • 8. Filters Figure: Low frequency Filter Figure: Low frequency Filter characteristics
  • 9. Figure: High Frequency Filter Figure: High Frequency Filter Characteristics
  • 10. Figure : 60 Hz notch filter Figure : 60 Hz notch filter characteristics
  • 11. Amplifier • All EEG amplifiers are differential amplifiers. • Differential amplifier takes two input voltages and produces an output that is an amplified version of the difference between the two inputs • Advantage – Cancels out the external noise
  • 12. Rules of Polarity on EEG  If input 1 is negative with respect to input 2, there is an upward deflection  If input 1 is positive with respect to input 2, there is a downward deflection  An upward deflection is surface negative, and a downward deflection is surface positive  When there is no deflection, the inputs are equipotential and are either equally active or inactive Equipotential
  • 14. Montage Logical and orderly arrangement of channels/electrode pairs on the display • Bipolar Montage • Common electrode reference montage • Average reference montage • Laplacian montage
  • 15. Figure : Commonly used bipolar longitudinal pattern (Double Banana) Figure : EEG of Bipolar montage
  • 16. Figure: Referential montage Figure: Laplacian montage
  • 17. Figure: Normal EEG in awake state
  • 18.
  • 19. EEG Artifacts • Artifacts are unwanted noise signals in an EEG record. • Classification of artefacts is based on the source of generation: Physiological artifacts and external artifacts. • Physiologic artifacts: • Any minor body movements • EMG • ECG • Eye movements etc. • Non Physiologic artifacts: • Damage of electrodes • Cable movements • Broken wire contacts • Impedance fluctuation • 60/50 H artifact etc Figure: EEG Artifacts
  • 20. Advantages & Applications of EEG • Excellent temporal resolution • EEG can determine the relative strengths and positions of electrical activity in different brain regions. • EEG does not involve exposure to high intensity magnetic field • Relatively cheap and simple to operate • Applications of the EEG in humans and animals involve:  Research  Clinics
  • 21.  Clinical application- EEG is one of the main diagnostic tests for epilepsy Normal EEG compared to EEG including a seizure: (A) Normal EEG of 15 seconds; (B) EEG of the same patient having an epileptic seizure visible on electrodes P8 and T8.
  • 22. Clinical applications • Monitor alertness, coma and brain death • Locate areas of damage following head injury, stroke, tumor. • Monitor cognitive engagement (alpha rhythm) • Control anesthesia depth • Investigate epilepsy and locate seizure origin • Investigate sleep disorder and physiology. • Etc.
  • 23. References • Teplan, M. (2002). FUNDAMENTALS OF EEG MEASUREMENT. • Britton JW, Frey LC, Hopp JLet al., authors; St. Louis EK, Frey LC, editors. Electroencephalography (EEG): An Introductory Text and Atlas of Normal and Abnormal Findings in Adults, Children, and Infants [Internet]. Chicago: American Epilepsy Society; 2016. Available from: https://www.ncbi.nlm.nih.gov/books/NBK390354/ • https://doi.org/10.1684/epd.2020.1217 • Light, G. A., Williams, L. E., Minow, F., Sprock, J., Rissling, A., Sharp, R., Swerdlow, N. R., & Braff, D. L. (2010). Electroencephalography (EEG) and event-related potentials (ERPs) with human participants. Current protocols in neuroscience, Chapter 6, Unit–6.25.24. https://doi.org/10.1002/0471142301.ns0625s52

Editor's Notes

  1. Summation of EPSP TRIGGERS AN ACTION POTENTIAL
  2. Volume Conduction: Bioelectric potentials’s flow from the source in the body to the recording electrodes.