Nina N. Danilova

The new method of microstructure analysis of oscillatory brain activity was pro­posed for studying the structure and dynamics of working memory. Mapping local network activity according to dipole localization of frequency-selective gamma and beta generators supports the leading role of frontal areas in processes of working memory. The retention of information during the delay interval is presented by joint activity of frequency-selective gamma and beta generators which provide the integration of frontal areas, associative, visual cortex and cerebellum. The joint activity of the gamma- and beta-generators has a wave-like character and is modulated by low-frequency wave activity.

Processing of sensory stimuli is controlled by the top-down influences that shape oscillations in the synchrony form revealed in the EEG. However, little is known about the nature of these influences. The present study investigated the contribution of "evoked oscillations" in the perception of auditory stimuli during passive and active attention from the position of pacemaker hypothesis on the origin of gamma rhythm. To analyze the problem, the author suggests a special method based on the narrow frequency filtering event-related potentials, localization of dipole sources of gamma oscillations over the structural MRI slices. Computation of equivalent dipoles for the discrete frequencies demonstrates interaction between prefrontal and auditory cortex during active attention to auditory stimuli. The obtained results are compatible with the pacemaker hypothesis.