What is Delta waves are seen in which stage of sleep? and explain in detail?
Ans. D. Deep SleepEEG waves:Delta:a. It has a frequency of 3Hz or below.b. It tends to be the highest in amplitude and the slowest waves.c. It is normal as the dominant rhythm in infants up to one year and in stages 3 and 4 of sleep.d. It may occur focally with subcortical lesions and in general distribution with diffuse lesions, metabolic encephalopathy hydrocephalus or deep midline lesions.e. It is usually most prominent frontally in adults (e.g. FIRDA - Frontal Intermittent Rhythmic Delta) and posteriorly in children e.g. OIRDA - Occipital Intermittent Rhythmic Delta).Theta:a. It has a frequency of 3.5to7.5Hz and is classified as "slow" activity.b. It is perfectly normal in children up to 13 years and in sleep but abnormal in awake adults.c. It can be seen as a manifestation of focal subcortical lesions; it can also be seen in generalized distribution in diffuse disorders such as metabolic encephalopathy or some instances of hydrocephalus.Alpha:a. It has a frequency between 7.5and13Hz.b. Is usually best seen in the posterior regions of the head on each side, being higher in amplitude on the dominant side.c. It appears when closing the eyes and relaxing and disappears when opening the eyes or alerting by any mechanism (thinking, calculating).d. It is the major rhythm seen in normal relaxed adults.e. It is present during most of life especially after the thirteenth year.Beta:a. It has a frequency of 14 and greater Hz.b. It is usually seen on both sides in symmetrical distribution and is most evident frontally.c. It is accentuated by sedative-hypnotic drugs especially the benzodiazepines and the barbiturates.d. It may be absent or reduced in areas of cortical damage. It is generally regarded as a normal rhythm.e. It is the dominant rhythm in patients who are alert or anxious or have their eyes open.