Electroencephalography (EEG) involves recording the electrical activity of the brain through electrodes placed on the scalp. Hans Berger first discovered EEG in 1924. EEG measures voltage fluctuations resulting from ionic currents within neurons. When neurons fire simultaneously, they create a wave that can be detected by electrodes. EEG is useful for studying brain function and diagnosing conditions like epilepsy by analyzing patterns of electrical activity.

1. RECORDING BRAIN ACTIVITY
- ASHISH BUDHWAR

2. RECORDING ELECTRICAL ACTIVITY OF THE
BRAIN
 The brain emits various electrical signals through the
neurons.
 These electrical signals can be useful in the study of
the functioning of the brain and its relation with the
behavior of organisms.
 Recording of electrical signals from the brain can be
obtained from the scalp by
ELECTROENCEPHALOGRAPHY

3. ELECTROENCEPHALOGRAPHY
 It was first discovered by German psychiatrist Hans
Berger in 1924.
 In this process, the ELECTROENCEPHALOGRAM
(the measure of the electrical activity of the brain) of
the human brain is recorded via a device called
ELECTROENCEPHALOGRAPH.
 The E.E.G measures voltage fluctuations resulting
from ionic current within the neurons of the brain.
 The fluctuations in the recording can signify
different conditions in the brain and the behavior
including normal activities, disease or disorder.

4. MECHANISM OF E.E.G
 The brain’s electrical charge is maintained by billions of
neurons.
 Neurons are electrically charged by membrane protein
that pumps ions across their membranes. Ions of similar
charges repel each other.
 When many ions are released from many neurons at the
same time, they push other ions which push further ions
thus creating a wave.
 When this wave of ions reaches the electrodes on the
scalp, a voltmeter detects the difference of voltage
between the electrodes.
 An E.E.G is a recording of these voltages over time.

5. E.E.G
 The scalp EEG signal reflects the sum of electrical
events throughout the head. These events include
action potentials and postsynaptic potentials as well
as electrical signals from the skin, muscles, blood,
and eyes.
 The utility of EEG as a research and diagnostic tool
rests on the fact that some EEG wave forms are
associated with particular states of consciousness or
particular types of cerebral pathology (e.g., epilepsy).
For example, high-amplitude waves are associated
with relaxed wakefulness.

6. ELECTROENCEPHALOGRAM

7. EVENT RELATED POTENTIALS
 ERPs are the EEG waves accompanying some
psychological activity in the background.
 By this method, the functioning of the brain while
the psychological activity is ongoing can be
ascertained.
 One common method of ERP is the SENSORY
EVOKED POTENTIAL.

8. SENSORY EVOKED POTENTIAL
 It is a method of ERP in which a momentary
stimulus is presented to the subject and the following
change in the cortical electrical activity of the brain
recorded via EEG is studied.
 The cortical EEG that follows the sensory stimulus
has 2 component, the response to the stimulus
(signal) and the ongoing background EEG activity
(noise). The signal is the part of interest for
researchers.

9. PROBLEMS FACED IN S.E.P
 The problem arises in the sensory evoked as the noise of
the background EEG is often so high that the signal
(response) to the stimulus gets masked. It can a like
detecting a whisper in a rock concert.
 To reduce the noise of the background, the method of
signal averaging is used. In this, first the subject’s
response to a meaningful stimulus is recorded for say
1000 times. Then the computer identifies the millivolt
value at each starting point then at the 1st millisecond,
then at 2nd millisecond and so on and finds their mean
and the random background EEG is cancelled out.

10. ANALYSIS OF AEPs
 The analysis of
average evoked
potentials (AEPs)
focuses on the
various waves in
the averaged signal.
Each wave is
characterized by its
direction, positive
or negative, and by
its latency.