5-12 Hz oscillations, observed in cortical local field potentials (LFP) of awake rats during quiet immobility, were proposed to be either (i) epileptic events or (ii) physiological alpha-like oscillations, manifesting an idling state of the cortex. In order to test this controversy we recorded LFP from the barrel cortex of awake rats, while applying weak tactile (whisker) and stronger arousing (electrical) stimuli. Tactile stimulation desynchronized the 5-12 Hz rhythm whereas arousal reduced their incidence and increased the desynchronizing abilities of tactile stimuli. Thus the 5-12 Hz oscillatory events should be interpreted as a physiological phenomenon typical for behavioral idling with maintained sensory sensitivity of the cerebral cortex.

The cover of this issue of Clinical Neurophysiology is an illustration from our article.