Experiments show that molluscs have a huge number of neurons not in the brain, but in the body and limbs. An octopus should be seen as an organism with one “brain” and intelligent limbs.

Scientists at the Okinawa Institute of Science and Technology have figured out how the octopus controls its eight limbs. Previously, researchers assumed that each of them has its own “brain.” It turned out that the brain of the mollusc receives information from tentacles.

“Some scientists think about octopuses as nine-brained creatures, with one central brain and eight smaller brains in each arm”

says Dr. Tamar Gutnick, an octopus researcher formerly at the Okinawa Institute of Science and Technology Graduate University (OIST).

The nervous system of octopuses consists of half a billion neurons, two-thirds of which are contained not in the brain, but in the body and limbs.

According to research, the tentacles use multiple reflex loops that allow them to act independently of the brain.

Scientists managed to find out that the tentacles are not completely independent of the animal’s brain. An octopus should be seen as an organism with one “brain” and smart limbs.

Experiments have shown that an octopus thrusting the tentacles into a Y-shaped maze with two branches is able to understand where food is, even if it does not see the food or the tentacle itself. Moreover, the animal remembers and next time slips the limb exactly where the food was kept earlier. This means that information is exchanged between the peripheral and central nervous systems.

“This study makes it clear that octopus’s arms don’t behave totally independently from the centralized brain—there’s information flow between the peripheral and central nervous system”

says Gutnick with adding that

“Rather than talking about an octopus with nine brains, we’re actually talking about an octopus with one brain and eight very clever arms”

It also turned out that the limbs also transmit tactile information. The octopuses slowly felt the branches, some of which were smooth, while others had a rough surface.

“The brain of octopuses is so different—it’s still a black box to us really. There’s so much more to learn”

Researchers concludes.