Recording Electrical Activity from the Brain of Behaving Octopus

Abstract

Octopuses, which are considered to be among the most intelligent invertebrates, have no skeleton and eight highly flexible arms whose sensory and motor activities are at once autonomous and coordinated by a complex central nervous system. The octopus’ brain is comprised of very large numbers of neurons, organized into numerous distinct lobes, the functions of which have been proposed based largely on the results of lesioning experiments. In other species, linking brain activity to behavior is done by implanting electrodes and directly correlating electrical activity with observed animal behavior. However, because the octopus lacks any hard structure to which recording equipment can be anchored, and because it uses its eight flexible arms to remove any foreign object attached to the outside of its body, in-vivo recording of electrical activity from behaving octopuses has thus far not been possible. Here we describe a novel technique for inserting a portable data logger into the octopus and implanting electrodes into the vertical lobe system, such that brain activity can be recorded for up to 12 hours from unanesthetized, untethered octopuses, and synchronized with simultaneous video recordings of behavior. In the brain activity we identified several distinct patterns that appeared consistently in all animals. While some resemble activity patterns in mammalian neural tissue, others, such as episodes of 2Hz,  large amplitude, oscillations have not been reported. This study provides the first insight into the brain activity of behaving octopuses, and represents a critical step towards understanding how the brain controls behavior in these remarkable animals.

Keywords: Octopus, Octopus Neurophysiology, In vivo, Central nervous system, Brain activity, Octopus behavior, Vertical lobe, infra-slow oscillations, data-logger