LEARNING AND OTHER FUNCTIONS OF THE HIGHER NERVOUS CENTRES OF SEPIA

Abstract

Four types of centre are recognized in the C.N.S. of Sepia, lower motor centres, higher motor centres at the base of the supraoesophageal ganglia, primary sensory centres and correlation centres which are the most dorsal lobes, known as the verticalis complex. Faradic stimulation of this complex produces no movements and after its complete removal the animal shows no superficial abnormalities and can steer, move around and feed as if normal. An animal so operated cannot however hunt its food when the latter disappears out of sight, a feat easily performed by a normal Sepia. If a normal Sepia is presented with a prawn behind a sheet of glass it will shoot its tentacles at the glass, but with a frequency which steadily diminishes. Removal of the verticalis complex disturbs this state of learned inhibition in various ways but does not destroy it completely, and relearning is still possible. 3 Sepia were trained not to eject the tentacles at a prawn showing behind a glass plate on which a white circle was painted, while continuing to shoot at prawns not accompanied by glass and circle.