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ELECTROENCEPHALOGRAM
(EEG)
AKASH KUMAR BHOI
Assistant Professor
SMIT
EEG
• The electroencephalogram (EEG) is a
recording of the electrical activity of the brain
from the scalp.
• The first recordings were made by Hans Berger
in 1929
Origin of EEG waves
Two types of recording
• Bipolar – both the electrodes are at active site
• Unipolar – one electrode is active and the
other is indifferent kept at ear lobe.
10 /20 % system of EEG electrode placement
10-20 System of
Electrode Placement
• F = Frontal
• P = Parietal
• T = Temporal
• O = Occipital
• C = Central
A = Auxiliary
• Odd # = Left
• Even # = Right
Factor influencing EEG
• Age
– Infancy – theta, delta wave
– Child – alpha formation.
– Adult – all four waves.
• Level of consciousness (sleep)
• Hypocapnia(hyperventilation) slow & high amplitude waves.
• Hypoglycemia (deficiency of glucose
in the bloodstream)
• Hypothermia
• Low glucocorticoids
Slow waves
Desynchronization or Alpha block
• Cause:
• Eyes opening (after closure)
• Thinking by the subject (mathematical calculation)
• Sound (clapping)
Eye opening
• Alpha rhythm changes to beta on eye opening
(desynchronization / α- block)
Thinking
• Beta waves are observed
Provocation test
• Intermittent photic stimulation
• Increase rate & decrease amplitude
• Hyperventilation
• Decrease rate & increase in amplitude
EEG
Different types of brain waves in normal EEG
Rhythm Frequency
(Hz)
Amplitude
(uV)
Recording
& Location
Alpha(α) 8 – 13 50 – 100 Adults, rest, eyes closed.
Occipital region
Beta(β) 13 - 30 20 Adult, mental activity
Frontal region
Theta(θ) 4 – 8 Above 50 Children, drowsy adult,
emotional distress
Occipital
Delta(δ) 0.5 – 4 Above 50 Children in sleep
EEG
EEG
Computerized EEG Machine
EEG
EEG
EEG
EEG
THANK YOU

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EEG

  • 2. EEG • The electroencephalogram (EEG) is a recording of the electrical activity of the brain from the scalp. • The first recordings were made by Hans Berger in 1929
  • 4. Two types of recording • Bipolar – both the electrodes are at active site • Unipolar – one electrode is active and the other is indifferent kept at ear lobe.
  • 5. 10 /20 % system of EEG electrode placement
  • 6. 10-20 System of Electrode Placement • F = Frontal • P = Parietal • T = Temporal • O = Occipital • C = Central A = Auxiliary • Odd # = Left • Even # = Right
  • 7. Factor influencing EEG • Age – Infancy – theta, delta wave – Child – alpha formation. – Adult – all four waves. • Level of consciousness (sleep) • Hypocapnia(hyperventilation) slow & high amplitude waves. • Hypoglycemia (deficiency of glucose in the bloodstream) • Hypothermia • Low glucocorticoids Slow waves
  • 8. Desynchronization or Alpha block • Cause: • Eyes opening (after closure) • Thinking by the subject (mathematical calculation) • Sound (clapping)
  • 9. Eye opening • Alpha rhythm changes to beta on eye opening (desynchronization / α- block)
  • 10. Thinking • Beta waves are observed
  • 11. Provocation test • Intermittent photic stimulation • Increase rate & decrease amplitude • Hyperventilation • Decrease rate & increase in amplitude
  • 13. Different types of brain waves in normal EEG Rhythm Frequency (Hz) Amplitude (uV) Recording & Location Alpha(α) 8 – 13 50 – 100 Adults, rest, eyes closed. Occipital region Beta(β) 13 - 30 20 Adult, mental activity Frontal region Theta(θ) 4 – 8 Above 50 Children, drowsy adult, emotional distress Occipital Delta(δ) 0.5 – 4 Above 50 Children in sleep