Cortical synchronization induced by thermal stimulation of the preoptic area in immobilized rats

Cortical synchronization characterized by frontal spindles and occipital slow wave activity was induced by bilateral thermal stimulation of 2--4 degrees C of the preoptic area in unanaesthetized immobilized rats. The synchronization was demonstrated by ECoG and its power density spectra. The ECoG of the synchronization was similar to that of slow wave sleep. Switching off the thermal stimulation the original activity was recovered in most of the cases. Frontal spindle activity and slow wave activity recorded over the posterior cortex seemed to be dissociated to some degree. Low frequency stimulation at the points of thermal stimulation resulted in frequency following synchronization. In some cases electrical and thermal stimulation induced gradually developing seizure activity.