The document discusses the basics and fundamentals of electroencephalography (EEG) and its measurement. It provides a timeline of EEG invention from 1875 to 1924. It describes cerebral generators of EEG potentials and how electrical signals propagate through neurons and are detected by EEG electrodes. The document outlines how EEG is recorded using a modern EEG machine and the 10-20 system for electrode placement. It discusses filters, amplifiers, polarity conventions, montages, artifacts, and clinical applications of EEG for monitoring brain activity and diagnosing conditions like epilepsy.

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

13. Polarity Convention - Example

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

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

24. Thankyou…