PROPIEDADES ELECTROFISIOLOGICAS DE LASVARIANTES NORMALES DE ACTIVIDAD ALFA EN ELCONTINUO VIGILIA-SUEÑO

Abstract

The study of cerebral rhythms ispossible by analyzing its electrophysiological features with quantitative EEG techniques. In the cases in which the same activity appears spontaneously in different brain states, the study of its electrophysiological features would help to establish functional differences associated to each of these states. The present work reviews those studies that determined the electrophysiological features of the different normal variants of alpha activity appearing in the wake-sleep continuous, more specifically, during relaxed wakefulness, drowsiness and REM sleep. The results indicate that each normal variant of alpha activity, in spite of showing a similar topographical distribution in each of the brain states, shows differentfeatures in relation to its spectral composition, functional relationships among cortical regions, and underlying brain micro-states. According to these experimental findings, each alpha variant would playa different brain function. Thus, the wakefulness alpha rhythm seems to reflect a maximum neuronal synchronization due to the absence of visual processing, whereas alpha activity during the drowsiness period would be associated with the brain processing of hypnagogic imagery happening at sleep onset. However, spontaneous alpha bursts ofREM sleep would reflect the contact between the.sleeping brain and the environment. Thiselectrophysiological characterization has its most direct applied field in the design of algorithms to stage sleep automatically, as well as in the diagnosis and evaluation of clinical entities in which the brain generator mechanisms ofthis activity could be affected through the wake-sleep continuous.