Electroencephalography is the technique used to acquire electrical signals of brain through electrodes which are placed by certain montage. Different wave patterns can be observed which is useful in detecting any abnormal conditions or neurological brain disorders in human beings. There is broad future scope for medical research and creating EEG based equipments for real time applications.

1. ELECTROENCEPHALOGRAM
(EEG)
Presented by
Vajarala Ashikh
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2. Introduction
 Electroencephalography is a technique that
records the electrical activity of the brain
 During an EEG test, small electrodes like cup or
disc type are placed on the scalp
 They pick up the brain's electrical signals and
send them to a machine called
electroencephalogram
 It records the signals as wavy lines on to a
computer screen or paper in order of microvolt
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3. History of EEG
 In 1875, Sir Richard Caton presented his findings
about electrical phenomena of the exposed
cerebral hemispheres of rabbits and monkeys
 In 1890, Sir Adolf Beck published an
investigation of spontaneous electrical activity of
the brain of rabbits and dogs
 In 1924, Sir Hans Berger recorded the first
human EEG
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4. Why EEG is used
 An EEG is mainly used when there is a need to
diagnose and manage epilepsy
 It can also be used to investigate other
conditions such as encephalitis, dementia, head
injuries, brain tumors, hemorrhage
 An EEG can identify areas of the brain that are
not working properly
 EEGs are also used to determine the level of
brain function in people who are in a coma
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5. Parts of Brain
 Cerebrum
 Frontal Lobe
 Parietal Lobe
 Temporal Lobe
 Occipital Lobe
 Cerebellum
 Brain stem
Parts of brain
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6. Source of EEG activity
 Neurons are electrically
charged by membrane
transport proteins that
pump ions across their
membranes
 When the wave of ions
reaches the electrodes on
the scalp, they can push or
pull electrons on the metal
of the electrodes
 Push or pull difference
measured as voltage across
time is referred as EEGElectrode on scalp
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7. Types of electrode placement
EEG electrodes placed
separately on scalp
EEG electrodes mounted as
special band on head
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8. International 10-20 System
International 10-20 System
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9. Closely spaced electrodes
Closely spaced electrodes
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10. Types of EEG
• Around 20 electrodes are stuck to the scalp using a special
paste and EEG signals are recorded
Routine EEG
• The EEG tracing will be recorded along with the heart rate,
airflow, respiration, oxygen saturation and limb movement
Sleep EEG
• It involves recording the brain activity throughout the day and
night
• A small portable EEG recorder is clipped on to the clothing
Ambulatory EEG
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11. Types of EEG electrodes
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Ear clip electrode
Disk electrodes
Intracortical electrodes

12. Electrode
Montage
Selector
Hi-pass Low-pass Notch Sensitivity
Amplifiers
Filters
Electrode
test/calibrate
Jackbox
Analog to digital
converter
Oscilloscope Computer
Chart
drive
Ink-writing
oscillograph
Writer unit
EEG
Subject
Electrodes
Schematic diagram of an EEG machine
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13. Montages
Sequential montage
• Each channel represents the difference between two
adjacent electrodes
Referential montage
• Each channel represents the difference between a
certain electrode and a designated reference electrode
Average reference montage
• The outputs of all of the amplifiers are summed and averaged
Laplacian montage
• Each channel represents the difference between an electrode
and a weighted average of the surrounding electrodes
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14. Wave patterns
 Delta waves
 Frequency range 0.5-4 Hz
 Slow-sleep wave for adults
 Theta waves
 Frequency range 4-7 Hz
 Drowsiness in older children and adults
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15.  Alpha waves
 Frequency range from 7-14 Hz
 Closing of the eyes, relaxation and attenuation with
eye opening or mental exertion
 Mu rhythm
 Frequency range from 8-13 Hz
 Shows rest-state motor neurons
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16.  Beta waves
 Frequency range 15 – 30 Hz
 Active, busy, or anxious thinking, active concentration
 Gamma waves
 Frequency range approximately 30–100 Hz
 Perception that combines two different senses, such as
sound and sight
 Short-term memory matching of recognized objects,
sounds, or tactile sensations
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17. EEG displaying epilepsy
EEG waveforms detecting epileptic spikes
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18. EEG Results
Normal EEG Abnormal EEG
 A brainwave pattern called
alpha rhythm should be
seen when sitting quietly
with eyes closed
 EEG results are
often normal because
recording a person's brain
activity during the times it
is abnormal is difficult
 People with epilepsy may
have abnormal brain
activity detected
 People who do not have
epilepsy may also have an
abnormal EEG result
indicating any other
disorder
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19. EEG Artifacts
• Mains voltage of 110/230 volts, exceeds the EEG's 50
to 100 microvolts by 126dB
• Amplifier notch filters are designed to suppress a
certain amount of mains interference
Mains
Interference
• Eye-induced artifacts - eye blinks, eye movements
• ECG and EMG induced artifacts
• Glossokinetic artifacts
Biological
Artifacts
• Movement by the patient, or even settling of the
electrodes
• Presence of an IV drip that can cause rhythmic, fast,
low-voltage bursts, which may be confused for spikes
Environmental
Artifacts
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20. Mains interference artifacts
Eye blink artifacts
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21. Artifact correction
 Independent component analysis techniques
have been used to correct or remove EEG
contaminants
 This would result in clean EEG by nullifying
(zeroing) the weight of unwanted components
 Surface Laplacian has been shown to be
effective in eliminating muscle artefact
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22. Risks and Precautions
 Slight redness may occur in the locations where
the electrodes were placed
 In rare cases, the cleaning liquid or paste may
cause temporary skin irritation
 The person is instructed not to take food that
contains caffeine
 Not to have oiled hair on the day of test
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23. Advantages
 Hardware costs are significantly lower than those of
most other techniques
 EEG has very high temporal resolution, on the order
of milliseconds rather than seconds
 Extremely non-invasive
 EEG is silent, which allows for better study of the
responses to auditory stimuli
 EEG does not involve exposure to high-intensity
(>1 Tesla) magnetic fields
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24. Disadvantages
 Low spatial resolution on the scalp
 EEG determines neural activity that occurs
below the upper layers of the brain poorly
 Often takes a long time to connect a subject to
EEG
 Signal-to-noise ratio is poor
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25. Uses of EEG
 Clinical Use
 Distinguish epileptic seizures from non-epileptic
seizures, syncope (fainting) and sub-cortical
movement disorders
 To serve as an adjunct test of brain death
 To determine whether to use anti-epileptic
medications
 Research Use
 Cognitive science, cognitive psychology, neuro -
linguistics and psycho physiological research
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26. Some more uses
 Investigate epilepsy and locate seizure origin
 Monitor cognitive engagement (alpha rhythm)
 Monitor human and animal brain development
 Test epilepsy drug effects
 Test afferent pathways (by evoked potentials)
 Investigate sleep disorder and physiology
 Control anesthesia depth
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27. Modern clinical EEG system
 It is a 36 channel cEEG system
 The system incorporates digital
video with the traditional EEG
 It is unaffected by electrical,
radio and magnetic interference
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28. Research on infant attention
 The goal of the research was to examine the
role of the brain in development of infant
attention
 Baby with EEG recording net that
measures 128 channels of EEG
activity
 Pictures and movies with sounds
were shown to check baby’s
response
infantlab.psych.sc.edu
Baby with EEG
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29. Recent Development
InteraXon EEG Headset
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30. Software for EEG
 EEG recording can be analyzed using various
programs
 EEGLAB
 Fieldtrip
 NBT
 Tucker-Davis Technologies
 Brainvision Analyzer
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31. Companies
 Some of these companies have built commercial
EEG devices
 NeuroSky
 OCZ Technology
 Square Enix
 Mattel
 Emotiv
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32. Future scope
Telepathic Helmets
Neuroheadset
 EEG has future advances in clinical, research, military & gaming industry
 Honda is attempting to develop a system to enable an operator to control
its Asimo robot using EEG
Future Portable EEG
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33. References
 Handbook of Biomedical Instrumentation-R.S Khandpur, 2nd edition
 Haas, L F (2003). "Hans Berger (1873-1941), Richard Caton (1842-
1926), and electroencephalography". Journal of Neurology,
Neurosurgery & Psychiatry
 www.nhschoices.com
 infantlab.psych.sc.edu
 www.ece.mcmaster.ca
 guile3d.com
 viasyshealthcare.com
 24megabytes.com
 tuckerdavistechnologies.com
 thefuturist.com
 E. Niedermeyer, F. H. Lopes da Silva. 1993. Electroencephalography:
Basic principles, clinical applications and related fields, 3rd edition,
Lippincott,Williams &Wilkins, Philadelphia
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34. Thank you
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