Study of the constant wave form of ML-AEP in humans

Wave forms of ML-AEP were studied in 21 healthy subjects and in 4 cases with well localized lesions in the brain. In order to obtain and define the constant wave form we used 5 mg of diazepam in these subjects. In awake state (before administration of diazepam) two types of muscle activity were observed. Postauricular muscle reflex (PMR), which follows high amplitude Na, Pa and Nb potentials, decreases its amplitude and seems to disappear when No and Po come out in light sleep (after administration of diazepam). The other type of muscle activity is derived from facial and other extracranial muscles associated with face or neck movements and deforms wave form in which we are unable to identify each component. These muscle activities cause the variability of wave form in awake state. In light sleep, wave forms were classified as follows: A, includes all components of ML-AEP; B, no Nb component; C, no No and Po components. The most constant waves are Na and Pa potentials and No, Po are variable in appearance. Sequential recordings from awake to light sleep suggested that No, Po are the remnants of PMR in light sleep. Studies of ML-AEP in 4 cases revealed attenuated or absent Na, Pa and Nb potentials. No and Po are variable in appearance in these cases in spite of different locations of lesions in the brain. These studies seemed to support the idea that No and Po are remnants of PMR in light sleep and the constant wave form of ML-AEP consists of Na, Pa and Nb potentials.