A STUDY OF SPONTANEOUS SPINDLE WAVES IN SENSORIMOTOR CORTEX OF CAT

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Abstract
Spontaneous spindle waves have been recorded on the surface and at measured depths in the sensorimotor cortex of the unanesthetized cerveau isole cat. The spatial and temporal distributions of slow potential changes and of unit activity during individual spindle waves have been described. Two basic time-depth potential patterns have been identified in association with individual spindle waves. The Type I pattern is initiated by a sink in layers III and IV which migrates to the surface and is associated with tightly clustered unit discharges in the deep layers. This pattern resembles that seen during augmenting waves evoked by stimulation of specific thalamic nuclei. The Type II pattern is characterized by a very superficial sink superimposed upon a deep sourcesink sequence and is associated with dispersed unit discharges in the deep layers. This pattern resembles that seen during recruiting waves evoked by stimulation of the diffusely projecting thalamic nuclei. In any single spindle burst the majority of individual waves are mixtures of these two patterns in which the Type I pattern invariably precedes the Type II pattern. Pure Type I waves are usually confined to the early waves of a burst while pure Type II waves are usually seen only near the end of a burst. The mechanisms involved in the production and the implications of the existence of these two types of spindle waves are discussed.