A blood flow increase to a visual stimulus in the occipital lobe of the cat with brainstem transection at the pretrigeminal level.

The effects of visual stimulation on the cerebral blood flow were studied in pretrigeminal cats. The visual stimulus was a feather duster which was moved for 4-5 min in front of the cats eyes. The cerebral blood flow was measured each 15 min with [133]Xe clearance method in the left occipital lobe. The visual stimulation evoked an increase of the cerebral blood flow which was accompanied by an ocular following movements and a cortical EEG desynchronization. The arterial blood pressure was unchanged. All these responses habituated rapidly when the stimulus was repeated at 15 min intervals. A similar increase of the cerebral blood flow was obtained by 9 percent CO2 inhalation. The administration of amphetamine increased the cerebral blood flow, whereas Nembutal decreased it. The visual stimulus evokes an increase of the cerebral blood flow in a condition when the lower brainstem is separated from the cerebrum.