LESIONS OF THE VERTICAL LOBE IMPAIR VISUAL-DISCRIMINATION LEARNING BYOBSERVATION IN OCTOPUS-VULGARIS

We investigated whether lesions of the vertical lobe of the supraesoph ageal nervous mass of Octopus vulgaris impair discrimination learning acquired by observation of conspecific behavior. When tested alone, ob server octopuses with about 50% of the vertical lobe removed showed a deficit in their learning by observation performance. The level of lea rning improved 24 h after the observational phase, when observer Octop us vulgaris showed a visual discriminatory performance significantly i n agreement with the observed one. Control animals that had no brain t issue removed, did not show any impairment in the discriminative perfo rmance they had acquired vicariously. Removal of the vertical lobe of the octopus 'brain' has been reported to induce learning and memory de ficits of visual discrimination in direct learning by conditioning exp eriments. Our findings support the conclusion that the removal of such brain center impairs short-term recall, but does not impair acquisiti on nor retention of 'observational' long-term memory.