Short-lasting memory in lower nervous centers in Octopus.

Octopuses with the supraesophageal lobes split and the subesophageal centers isolated by cutting the cerebrobrachial connective on one or both sides were trained by food and shock rewards to discriminate between rough and smooth balls. Because there is a greater tendency to take the rough ball, training was done with the smooth ball positive for half the animals, and the rough ball positive for the others. In the animals with the cerebrobrachial connective cut only on one side, the subesophageal lobes showed no capacity to use the information gained by their opposite, intact, half-brains, which learned well. In animals with isolated subesophageal lobes, there was a decrease during each training session in the tendency to take both types of ball; however, this decrease did not persist from day to day. During each training session there were signs of discrimination between the balls by animals with isolated subesophageal lobes, but these also did not survive from day to day. In a series of training sessions spread over seven weeks, there was no change in results in animals with isolated subesophageal lobes when the smooth ball was positive. When the rough was positive the discrimination in its favor was slightly increased at later sessions.