The Effect of Lesions to the Vertical and Optic Lobes on Tactile Discrimination in Octopus

Abstract

1. Blind octopuses were trained to make tactile discriminations between the members of pairs of objects and their performance was compared with that of other blind animals having. parts of the brain removed. 2. It was found that removal of the optic lobes, together constituting more than half of the total mass of the brain, did not affect the performance of animals in these discrimination 3. Removal of the vertical lode, on the other hand, produced deficiencies proportiante to the amount d tissue removed; these deficiencies were mat marked in the cose of the more difIicult of the two discrimination problems used in the tests. 4. It was possible to compensate for loss of the vertical lobe to a considerable extent by arranging trials at more frequent intervals. Animals unable to learn a tactile discrimination when trained at rate of 8 trials per day did so when trained at 40 trials per day. 5. When animals trained at the latter rate were subjected to reversed training, thoselacking the vertical lobe re-learned in fewer trials than controls, indicating shorter persistence of the effects of pre-reversal training. 6. It is concluded that the vertical lobe is concerned with the persistence of conditions set up in the nervous system as a result of sensory experience. It is not known whether the vertical lobe serves to increase the initial intensity of these conditions, or to delay their decay.