Brain stem structures responsible for the electroencephalographic patterns of desynchronized sheep.

Contrary to the results of transecting one half of the rostral pons, unilateral partial lesions of the rostral pons, involving either "specific" or "aspecific" structures, do not prevent the appearance of the desynchronized electroencephalographic patterns of deep sleep in the ipsilateral hemi sphere in cats. This effect, however, is obtained by lesions of the medial as well as lateral tegmental structures of the midbrain. These findings seem to indicate that (i) there is not a single pontine structure or group of structures of crucial importance for the EEG desynchronization of deep sleep; the whole rostral pons appears to contrib ute to the EEG-desynchronizing influ ence; (ii) this influence runs rostrally through the midbrain tegmentum, without following any known fiber pathway.