Delta waves on EEG are recorded in:September 2007

Ans. D: Deep sleepAlpha waves generally are seen in all age groups but are most common in adults.They occur rhythmically on both sides of the head but are often slightly higher in amplitude on the nondominant side, especially in right-handed individuals.A normal alpha variant is noted when a harmonic of alpha frequency occurs in the posterior head regions.They tend to be present posteriorly more than anteriorly and are especially prominent with closed eyes and with relaxation.Alpha activity disappears normally with attention (e.g., mental arithmetic, stress, opening eyes).In most instances, it is regarded as a normal waveform.An abnormal exception is alpha coma, most often caused by hypoxic-ischemic encephalopathy of destructive processes in the pons (e.g., intracerebral hemorrhage).In alpha coma, alpha waves are distributed uniformly both anteriorly and posteriorly in patients who are unresponsive to stimuli.Beta waves are observed in all age groups.They tend to be small in amplitude and usually are symmetric and more evident anteriorly.Drugs, such as barbiturates and benzodiazepines, augment beta waves.Theta waves normally are seen in sleep at any age. In awake adults, these waves are abnormal if they occur in excess. Theta and delta waves are known collectively as slow waves.Delta waves are slow waves have a frequency of 3 Hz or less.They normally are seen in deep sleep in adults as well as in infants and children.Delta waves are abnormal in the awake adult.Often, they have the largest amplitude of all waves.Delta waves can be focal (local pathology) or diffuse (generalized dysfunction).