[ 59 ° 1 a Touch - Learning Centre in Octopus

INTRODUCTION Octopuses blinded by section of their optic nerves can be trained to discriminate between the members of pairs of objects touched (Wells & Wells, 1956, 1957a). Removal of the optic lobes—more than half of the total mass of the brain—does not affect their performance in such discriminations (Wells & Wells, 19576), but removal of a comparatively small amount of tissue from the vertical lobe, lying on top of the central supraoesophageal brain mass, produces deficiencies that may be broadly described as decreasing the efficiency of the learning process; after operation a greater number of trials is required to reach prescribed standards of response in training experiments. The nature of the deficit caused by vertical lobe removal has been considered for tactile discriminations by Wells & Wells (19576, c, 1958a, 6) and for visual discriminations by Boycott & Young (1955, 1957)The present account deals with the results of supraoesophageal lesions that extend beyond the optic-vertical lobe system and include the basal lobes. The latter form the greater part of the central supraoesophageal brain mass and are known to be concerned with the integration of movements of the animal as a whole (Boycott & Young, 1950, i960); the part they play in learning cannot be investigated using visual techniques comparable with those used to investigate vertical lobe function (Boycott, 1954) since their removal upsets motor co-ordination and prevents the animal from attacking or retreating from things seen. The problem has therefore been approached using tactile training techniques involving movements of only one arm at a time that are co-ordinated within the arm concerned. It will be shown that while the basal lobes play no part in learning to recognize things touched, the areas immediately anterior to them, the inferior frontal and subfrontal lobes, are essential; without them an octopus cannot be taught to discriminate between objects that it touches. MATERIAL