Oscillatory Activity and Cross-frequency Interactions during the Processing of Sensory Information in the Brain

Oscillations, or rhythms, are necessary for the execution of many cognitive functions as they provide fast and flexible changes in neuronal interactions in different brain structures [Fries, 2005; Womelsdorf et al., 2007]. Until recently insufficient attention was paid to the question of how different types of oscillations are synchronized during the processing of the information coming to the brain. In the present work the expressiveness and correlation of rhythmic activity in the theta, alpha and gamma ranges in animals in two behavioral states were analyzed: during quiet wakefulness and during perception of sensory signals. Local field potentials (LFPs) in eight brain structures (cortical and subcortical) were registered. In many areas, an increase of oscillatory activity during the presentation of external signals was revealed. The main result of the present work is the detection of a sharp increase of cross-frequency relations in all oscillatory bands, both in the cortical and subcortical structures during the processing of sensory information. It is supposed that an increase of synchronization of rhythmic activities in different brain areas is necessary for detailed assessment of environmental signals and their registration in the memory system.