Cortical independence of type I and II barbiturate spindles

Two varieties of barbiturate-induced EEG spindles are recognized. Type I originates subcortically but recent data suggest that type II spindles are triggered by type I at the cortical level. This is based on a temporal relationship between the two spindle types in the gross electrocorticogram. In the present study no such relationship could be found except possibly in light anesthesia. These results fail to confirm the only data supporting a cortical mechanism underlying type II spindles.