A Survey: Fundamental of EEG, by Shamla Mantri1, et.al.
This is broad view of the value and forms of an EEG.
Recent advances in computer hardware and signal processing have made possible the use of EEG signals or “brain waves” for communication between humans and computers. Hence there is need to know about EEG signal. Electroencephalogram (EEG) is the recording of the electrical activity of the brain. The EEG signal is a representative signal containing information about the condition of the brain. The shape of the wave may contain useful information about the state of the brain. It has been known that different regions of the brain are activated according to the associated mental status, for example, emotional status, cognitive status, etc. Since the difference in activities of the brain causes the difference in characteristics of EEG, it has been attempted to investigate the brain activity through analyzing EEG.
Here is a glimpse of the INTRODUCTION
The group of electrobiological measurements comprises items as electrocardiography (ECG, heart), electromyography (EMG, muscular contractions), electroencephalography (EEG, brain), magnetoencephalography (MEG, brain), electrogastrography (EGG, stomach), electrooptigraphy (EOG, eye dipole field).
Imaging techniques based on different physical principles include computer tomography (CT), magnetic resonance imaging (MRI), functional MRI (fMRI), positron emission tomography (PET), and single photon emission computed tomography (SPECT).
The article explains the value of the EEG signal -‘because it directly MEASURES the electrical activity of the brain and we know that brain in main part of the body. Electroencephalography is a medical imaging technique that reads scalp electrical activity generated by brain structures. The electroencephalogram (EEG) is defined as electrical activity of an alternating type recorded from the scalp surface after being picked up by metal electrodes and conductive media.’
They significantly explain that it is a ‘completely non-invasive procedure that can be applied repeatedly to patients, normal adults, and children with virtually no risk or limitation.
‘When brain cells (neurons) are activated, local current flows are produced. EEG measures mostly the currents that flow during synaptic excitation of the dendrites of many pyramidal neurons in the cerebral cortex. Differences of electrical potentials are caused by summed postsynaptic graded potentials from pyramidal cells that create electrical dipoles between soma (body of neuron) and apical dendrites (neural branches).
Due to capability to reflect both the normal and abnormal electrical activity of the brain, EEG has been found to be a very powerful tool in the field of neurology and clinical neurophysiology.
The human brain electric activity starts around the 17-23 week of prenatal development.’
The article then gives a brief history of EEG, from the early identification of the electrical current by in the brain in 1875 by the English physician Richard Caton.
Later, in 1924, a German neurologist, Hans Burger, amplified the electrical activity given off outside the scalp, using general radio equipment. He recorded this on scratches drawn on a strip of paper.
Berger noticed that the quality and level of activity – brain waves – changed during different mental and physical functions and conditions. Sleep, low levels of oxygen were useful indicators. ‘He was right with his suggestion that brain activity changes in a consistent and recognizable way when the general status of the subject changes, as from relaxation to alertness.’
Berger began the foundations for many of the present applications of electroencephalography, but real interest in the subject took some time before it become mainstream.
‘In 1934 Adrian and Matthews published the paper verifying concept of “human brain waves” and identified regular oscillations around 10 to 12 Hz which they termed “alpha rhythm”’
There are ‘several waves that can be differentiated from the EEG signal alpha, beta, gamma, theta etc’.
The Paper is availible online at: http://www.ijarcsms.com A Survey: Fundamental of EEG