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Electroencephalogram(EEG)

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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.

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Electroencephalogram(EEG)

  1. 1. ELECTROENCEPHALOGRAM (EEG) Presented by Vajarala Ashikh 1
  2. 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 2
  3. 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 3
  4. 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 4
  5. 5. Parts of Brain  Cerebrum  Frontal Lobe  Parietal Lobe  Temporal Lobe  Occipital Lobe  Cerebellum  Brain stem Parts of brain 5
  6. 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 6
  7. 7. Types of electrode placement EEG electrodes placed separately on scalp EEG electrodes mounted as special band on head 7
  8. 8. International 10-20 System International 10-20 System 8
  9. 9. Closely spaced electrodes Closely spaced electrodes 9
  10. 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 10
  11. 11. Types of EEG electrodes 11 Ear clip electrode Disk electrodes Intracortical electrodes
  12. 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 12
  13. 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 13
  14. 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 14
  15. 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 15
  16. 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 16
  17. 17. EEG displaying epilepsy EEG waveforms detecting epileptic spikes 17
  18. 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 18
  19. 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 19
  20. 20. Mains interference artifacts Eye blink artifacts 20
  21. 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 21
  22. 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 22
  23. 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 23
  24. 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 24
  25. 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 25
  26. 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 26
  27. 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 27
  28. 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 28
  29. 29. Recent Development InteraXon EEG Headset 29
  30. 30. Software for EEG  EEG recording can be analyzed using various programs  EEGLAB  Fieldtrip  NBT  Tucker-Davis Technologies  Brainvision Analyzer 30
  31. 31. Companies  Some of these companies have built commercial EEG devices  NeuroSky  OCZ Technology  Square Enix  Mattel  Emotiv 31
  32. 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 32
  33. 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 33
  34. 34. Thank you 34

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