A REPORT / COURSE WORK.

A
REPORT / COURSE WORK
ON
ELECTROENCEPHALOGRAPH (EEG):
BASIC BRAIN WAVES, WORKING, QUANTIFICATION
AND
DESIGN OF DIGITAL FILTER IN MATLAB
In partial fulfillment for the award of the Degree of
BEng (GCU) IN Electronics and Instrumentation Engineering
Submitted by
NAME:
Reg no:
Bio-Medical Instrumentation
MHH624668

ACKKNOWLEDGEMENT
I take this opportunity to express my sincere gratitude and deep regards to my supervisor
NAME, DESIGNATION for guiding me throughout my entire course work technically and
methodologically.
I would like to thank all the teaching and non-teaching staffs of Dept and Institute name, for
providing enormous support to carry out my research works. I would like to thank all my
colleagues of Institute name, for providing their support in various manners during my course
works.

Abstract: This documentation describes the basic brain wave patterns, associated
with Electroencephalograph (EEG). The fundamental knowledge about neuronal
waves, attributes of the signals, different sensing devices and quantification methods
are discussed .The next section delineates the signal conditioning part of the system:
designing and implementing an IIR-Butterworth filter in Matlab. The designed filter
can wipe out the external noise interference, which deform the actual EEG signal
during the process of recording in hospital.
Introduction:
EEG is a bio-signal generated from the neuronal cell oh human mind. This is
basically the action potential of the neurons due to the movement of Na+, K+, and Cl-
ions present in cell. This action potential is picked up by sensors and analysed for
estimating the state of mind. Specially used for diagnosis and treatment purpose.
Now-a-days EEG signal processing is very popular and widely used for BCI, Brain
Computer Interface. The researcher design and implement different algorithm to
analyse the features present in the bio signals. It is claimed that the change in
pattern of alpha and beta band actually indicates the state of human mental state.
EEG signal measurement is very challenging because of their very low amplitude
and frequency components and its get affected and distorted by the external
interference and noise. As any movement in the body causes different artifacts which
affect the EEG signal recording.
I. Fundamentals
a) The brain waves are classified based on the frequency components
(Whittingstall, 2009) present in acquired signal. They are classified as Gamma
(γ), Beta (β), Alpha (α), Theta (θ), and Delta (δ). The brain waves with their
different features and patterns are discussed below.
 Gamma (γ): The frequency band responsible for γ, ranges from (35 –
42) Hz. It defines the human brain state is highly active and
concentrated. Though it may vary from one subject to another (Keren,
2010).
Fig. 1. Gamma: High frequency and amplitude
 Beta (β): Functional frequency range of Beta is within 12 – 35 Hz,
reflecting a state of mind related to relaxed, normal awaking and active
thinking.

Fig. 2. Beta: Relaxed awaking state
 Alpha (α): The characteristics of this wave analogous to drowsiness,
rest and inattention condition of mind. The frequency lies within 8 – 12
Hz.
Fig. 3. Alpha: Resting and inattentive state
 Theta (θ): The waves occur normally in sleep, dream, imagery and
intuition, where consciousness slips into drowsiness (Brod, 2018). The
voltage peak as well as frequency value reduces with the eyes keeping
closed. Band ranges in 4 – 8 Hz.
Fig. 4. Theta: Twilight state as drift off to sleep
 Delta (δ): Very low and deeply penetrating brain waves. Ranges from
0.5 – 4 Hz frequency. They are produced in deepest meditation and
dreamless sleep (Feinberg, 2010). It is accounted for slow wave sleep
pattern.
Fig. 5. Delta: Very low frequency and amplitude
b) The difference in bio-potential, produces in neuron is acquired by sensors,
called Electrodes. The measurement of bio-signals can be done in two ways:
Bipolar and Unipolar.
Bipolar Electrodes: Two equal size electrodes are placed to sense the bio-
signal. One is acting as a measuring electrode and another as reference
electrode. That means for each channel we need one reference electrode.
Unipolar Electrodes: Here a common reference electrode is used for all the
channels. The reference electrode is positioned in a zero or indifferent area,
eg: Left ear lobe. One small active electrode and another large dispersive
electrode are used.
The following figure shows both types of lead connections.