[Topography-reactivity and interhemispheric asymmetry of drug-induced beta activity in normal subjects--quantitative aspects].

Based on the spectral analysis of drug-induced beta activity in 15 normal subjects, the authors distinguish 2 groups of beta spectra: (1) Peaked beta spectra with stable frequency (25 +/- 0.3 Hz) and an essentially precentral localization. Such spectra must depend on the activation of a dense and circumscribed population of neurons having strong synchronizing power. (2) Beta spectra widely dispersed with regard to frequency and topography, having generators that are more widely distributed or with a lesser power of synchronization. The spectra show significant interhemispheric energy asymmetries which are accentuated by eye opening. Finally, these two types of beta activity, although exhibiting a preferentially precentral localization, are not altered by movements. In contrast they react, while maintaining energy to eye opening by energetic changes, which allows one to distinguish these activities from sensorimotor rhythms.