Acquisition of Conditioned Reactions to Angular Acceleration After Cortical Lesions

Abstract

Conditioned reactions (CR) to angular acceleration and discrimination of the direction of the accelerated rotation were previously demonstrated (Spiegel and Oppenheimer 1 ). Experiments on laby-rinthectomized dogs indicated that discrimination of direction of rotation in the horizontal plane at low acceleration is an important criterion of the analyzing function of the labyrinth. Since the changes in the electro-corticogram produced by stimulation of the labyrinth (Spiegel. 2 Kornmueller, 3 Price and Spiegel, 4 Gerebetzoff 5 ) suggest that labyrinthine impulses reach the cerebral cortex, it seemed of interest to ascertain to what extent cortical centers participate in the development of these reactions, and the ability of dogs with cortical lesions (2 frontal, 2 parietal and 2 temporal lobectomies) to acquire these CR was studied. One frontal and both parietal lobectomies were performed in one stage, one frontal and both temporal lobectomies in two stages. 14-51 days after the last operation conditioning was started. The dogs were rotated as previously 1 described in clockwise or counterclockwise direction first at slow constant speed which later passed smoothly into accelerated rotation. During the counterclockwise accelerated rotation the unconditioned stimulus (electric shock) was applied, while it was omitted during clockwise rotation. The reactions of the leg and the respiration were recorded. The animals were usually tested every 2nd or 3rd day, but in some cases longer rest periods (up to several weeks) were intercalated.

In both dogs with bilateral ablation of the parietal lobes CR to angular acceleration were obtained in the first test series; discrimination of direction developed on the third day of experimentation in dog No. 506 in which conditioning was started 26 days after bilateral parietal lobectomy and somewhat later in dog No. 486 (inconstant discrimination on the fifth day, constant discrimination on the seventh day); in this dog conditioning was started 17 days after operation.