ELECTRO ENCEPHALO GRAM (EEG):::
Nerve cells show changes of electrical potential during their activity The current generated by neurons in the brain is conducted by the surrounding fluids to the scalp and can be recorded The graphic record of such activity is called electroencephalogram (EEG)
Type of waves ::
Several types of waves have been identified which differ in frequency and potential (voltage) However four major types of waves common in human subjects are (1) alpha (2) beta (3) theta and (4) delta
Alpha waves ::
These waves are produced when an individual is relaxed especially with the eyes closed or has just awakened from a restful sleep they disappear with any visual stimuli (opening of the eye) or mental concentraction Alpha waves are usually found in occipital cortex but may also appear in frontal and parietal regions The amplitude of these waves is about 50 microvolts and rate 8-12 cycles per second
Beta waves ::
These are produced during mental activity or arousal They are found in parietal and frontal regions of the scalp They have a frquency of 13-32 per second and are of 5-10 microvolts
Delta waves :::
These are produced during the state of unconsciousness and deep sleep They occur at the rate of about 0.5-3.5 per second with a potential of 20 to 200 microvolts
Theta waves :::
These waves are aften formed during disappointment and frustration in young children and adolescents They are usually found over the parietal and temporal regions of the brain They occur at the rate of 4 to 7 per second and their potential is 10 microvolts
FIG NORMAL EEG GRAPH
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