Paired centres for the control of attack byOctopus

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Abstract
The vertical lobe system in Octopus is concerned in the regulation of the tendency to attack. It receives impulses from the optic lobes, from touch and chemoreceptors and from pain receptors. The visual part of the system is organized into lower and upper loops. The lower loop leads from the optic lobes, through two centres and back to the optic lobes. The upper loop also consists of two centres, superposed in parallel above the lower ones. Each of the two loops thus contains two centres in series and it is suggested that the first centre of each pair tends to promote attack and the second to restrain or prevent it. The net effect of the two centres of each pair together is to increase the probability of attack, unless pain intervenes. After any interruption of the lower loop an octopus does not launch out to attack a crab moving in its visual field, although it still puts out an arm to take a crab that is within reach. The impulses set up in the visual system cannot release an attack without the "amplification" produced by the centres of the lower loop. After interruption of the upper loop the octopus is still able to attack but the animals make errors both in failure to attack when rewarded with food and in continuing to attack in spite of shocks. Individual untrained octopuses were found to show consistent differences, in tendency to attack crabs, and these differences survived anaesthesia and dummy operation. However, any interruption of the upper loop tended to reverse the previous attack tendency. When the tendency to attack was high it was decreased by removal of the median superior frontal but not by removal of the vertical lobes. Removal of the median superior frontal after the vertical leads to a reduction in attacks, but removing the vertical after the superior frontal was followed by an increase. This evidence that the median superior frontal increases the tendency to attack and the vertical lobe reduces it was confirmed at longer periods after operation. Attacks at crabs in spite of shocks continued longer after removal of either lobe than in controls, but more attacks were made by animals without vertical than without median superior frontal lobes. The main output of the superior frontal is through the vertical and thus any injury affects both functions. However, severing the tract between them or removing both of them produced effects different from removing either alone. Each therefore has some effect when acting in isolation, though they normally operate together to influence the attack behaviour. There was greatly increased variability between individuals and within the performance of each individual after any interference with the vertical lobe system. This upper loop thus serves to produce stable and consistently adaptive behaviour, in addition to other effects that it may have in the process of learning.

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