Desynchronization

Desynchronization 

(of an electroencephalogram), the replacement of time-ordered, synchronous high-amplitude (30-100 microvolts [μv ]) and slow (α and θ-activity) oscillations of biopotentials by less regular, low-amplitude (5-25 μV) and faster (β-activity) oscillations. The desynchronization of biopotentials in the cerebral cortex usually occurs in response to various stimuli (see Figure 1) but may be caused, for example, by some pharmaceuticals. Desynchronization is one version of the “activation reaction,” or the “waking reaction,” in which the leading role is played by influences exerted on the cortex of the formatio reticularis. Desynchronization also sets in during particular stages of sleep (the fast phase of sleep, or “fast” sleep). Desynchronization is a manifestation of the orientation reflex.

Figure 1. Human electroencephalogram. At rest a regular α-rhythm with a frequency of 10 periods per second is recorded on pickups from various regions of the brain (at left). In response to a light stimulus (the dark band at bottom) the α-rhythm is replaced by low-amplitude β-activity. Scale: 50 μV along the vertical, 1 sec along the horizontal.

Persistent desynchronization (a so-called flat electroencephalogram) is one indication of disruption of the activity of the central nervous system.

E. A. ZHIRMUNSKAIA