[Spatio-temporal organization of ECoG spindles during sleep onset]

Spatio-temporal organization of spindle activity in the cerebral cortex during deepening of slow-wave sleep (SWS) was studied in experiments on cats and rabbits. Patterns of both "sleep" and recruiting reaction spindles were analyzed. In the process of sleep development spindle activity was transformed from local to a diffuse one, organized in a sort of packages. The rate of synchroneity in spindle packages depended on the sleep depth. At the deepest SWS stages a sharp desynchronization of spindles in the packages was observed and then--complete disappearance of spindle activity. Interaction of thalamic spindle pacemakers seems to play an important role in the mechanism of SWS development; changes in it result in reorganization of spindle activity on the cortical surface. A considerable part in this interaction is reserved to the processes of emergence and spread of delta-activity.