EEG is used to record the electrical activity of the brain. It uses electrodes placed on the scalp that are smaller than those used in ECGs. EEG can be used to diagnose neurological disorders like epilepsy. There are different types of brain waves like delta, theta, alpha, beta, and gamma waves that are defined by their frequency ranges and locations in the brain. Evoked potentials involve stimulating specific sensory pathways and measuring the electrical response in certain brain areas to help diagnose conditions.

1. BY: LOKENDRA YADAV

2. ELECTROENCEPHALOGRAP
H
ELECTROENCEPHALOGRAPH

3. EEG is an instrument used for recording of
electrical activity of brain. EEG electrodes
are smaller than ECG. The activity measured
by EEG are electrical potential created by the
post-synaptic currents. Its an effective
method for diagnosing many neurological
disorder such as epilepsy,tumour,etc.

5.  Biological artifact-
1. Eye-induced artifacts
2. Cardiac artifacts
3. Muscle artifacts
 Environmental artifacts

6. ELECTRODES
In general 25 electrodes are used in general
EEG test but no of electrode may vary as per
the EEG requirement and area of investigation
In 25 electrode EEG
system
23 electrode are
active electrodes
1 is ground electrode
1 is ref electrode

7. It’s a method to describe and apply the location
of scalp electrodes. This system is based on
the relationship between the electrode and
underlying cerebral cortex. The 10 and 20 refer
the actual distance between the adjacent
electrodes

9. BLOCK DIAGRAM
OF EEG

11.  Montages
 Electrode montage selector
 Preamplifier
 Sensitivity control
 Filters
1. Low pass filter
2. High pass filter
3. Notch filter

12.  Analog to digital convertor
 Writing unit

13.  Delta wave
 Theta wave
 Alpha wave
 Beta wave
 Gamma wave

14. Its frequency range is 1-4hz. It can be recorded
with an electroencephalogram and usually
associated with slow wave sleep (SWS).
Location: frontally in adults, posteriorly in
children; high amplitude waves

15. Two types of theta wave described as:
Hippocampal theta wave which is observed in
hippocampus and cortical theta wave which
low frequency component of scalp EEG
frequency range from 4-7Hz

16. Alpha waves are detected by
electroencephalography and
magnetoencephalography. Its mainly originated
from occipital lobe during relaxation with
closed eyes. Its frequency range is 8-12 hz.
Location: posterior regions of head, both sides,
higher in amplitude on dominant side. Central
sites (c3-c4) at rest .

17. Its frequency range is 12-30hz. Beta activity is
increased when movement have to be resisted.
beta waves have three sections: high beta
waves(19hz), beta waves(15-18hz), low beta
waves (12-15hz).
Location: both sides, symmetrical distribution,
most evident frontally; low amplitude waves

18. Its frequency range is 25- 100hz.
Location: Somatosensory cortex

19.  EEG voltage signals represent differences
between two electrode that can be between
two active electrode or between reference
electrode and active electrode.
 In adult EEG amplitude lie between 10
microvolts to 100 microvolts from scalp.
 And 10-20mv when measured from subdural
electrode

20.  Evoked potentials are used to measure the
electrical activity in certain areas of the brain
and spinal cord. Electrical activity is produced
by stimulation of specific sensory nerve
pathways.

21. Types of evoked potentials
 Visual Evoked Potentials (VEP): the patient sits
before a screen in which alternating patterns are
displayed.
 Auditory Evoked Potentials (AEP): the patient listens
to a series of clicks in each ear.
 Sensory Evoked Potentials (SEP): short electrical
impulses are administered on the arm or leg.
 Motor Evoked Potentials: these can detect
disruption on a motor pathway of the brain or
spinal cord.

22. Few applications of evoked
potential recording
BERA (brain evoked response
audiometry)
VEP test (visual evoked
potential test)
Brain evoked test for multiple
sclerosis

23.  For rapid and accurate interpretation, it need
constant analysis of the EEG. Therefore,
computerized EEG signal processing to extract
the frequency and amplitude in simple form.

24.  QUES…????
QUERY..???

25. THANK YOU