A study, led by researchers from the Hebrew University, provides the first proof that the octopus's brain receives information from the arms regarding their position or movement. It also shows for the first time that there is control between the brain and the arm in real time, that is, the exchange of sensory information from the arm to the brain at a relatively high speed in order to make a decision regarding the continuation of its movement
The collection of sensory information and the ability to learn, process it and respond accordingly is an essential aspect of animal behavior. Octopuses, which are considered to be the most intelligent animals among invertebrates although the exact nature of their intelligence is still unclear, provide us with a unique system for studying the relationship between sensory information, neural processing and motor activity. It is now known that octopuses have the largest nervous system among invertebrates, larger than some vertebrates (such as mice, for example), with more than half of the nerve cells located outside the brain, in the body and in the flexible arms.
Until now it was accepted that the movement and the processing of the sensory information was done in the arms
Does an octopus have multiple brains? Many researchers are still confused and grappling with this question. In the past, evidence was presented that each of the octopus's arms sometimes functions independently, without exchanging information between them and without intervention from the central brain, while in other cases a single control factor is presented that coordinates the activity of the arms. In any case, in each of the eight arms of the octopus there are hundreds of snap buttons with thousands of sense cells for taste and touch (you can compare this to eight arms with hundreds of tongues). The brain of humans and vertebrates has a representation of the body, and the greater the number of sensory cells in a certain organ (such as the tongue or a finger), the larger the area in the brain that represents it. In octopuses, no evidence of body mapping has yet been found in the upper parts of the brain. This is one of the reasons many researchers believed that the octopus brain receives very limited information from the arms, And most of the movement and sensory information processing is done in the arms themselves.
Many studies conducted in recent years in Prof. Benny Hochner's research group at the Hebrew University support the idea that during evolution octopuses adapted to themselves the "strange" structure of their body, and the unique organization of their nervous system in order to allow octopuses to function very efficiently even in the absence of body representation in the central nervous system. "It is important to understand that unlike our body, where the number of joints is relatively limited, the representation of a flexible body like that of the octopus (which can be imagined as consisting of an infinite number of joints) would require a nervous system of unrealistic size and complexity. In other words, it is the 'embodied organization' of the mutual and complex adaptation between the body and brain of the octopus that underlies the adaptation of the octopus to its environment," explains Prof. Hochner.
In a new study carried out by Prof. Hochner, Dr. Michael Koba and Dr. Tamar Gutnik from the Department of Neurobiology at the Institute of Life Sciences at the Hebrew University, in collaboration with a researcher from Italy - Letizia Zulu, from the Center for Bio-Robotics at the Italian Institute of Technology, and published in the scientific journal "Current Biology ", the learning abilities of the octopus were tested and the level of information received from the arms was tested. The researchers built two Y-shaped 'mazes' inside the aquariums where the octopuses were found, allowing them to use only one arm to find the correct side where their food source was. The octopuses could not see the arm or the food inside the maze, but learned that in order to get the food they must insert an arm into the maze and rely solely on sensory information from the arm moving through the 'maze'.
How does the octopus feel its body?
"The research focused on two senses. The first, proprioception, self-sensing of the body, meaning the ability to "know" where my arm is or what it's doing even when I can't see it, since the octopuses are unable to see their arms inside the maze. In humans, a central part of this sense relies on sensory cells between the skeletal muscles and joints, and these are of course not found in octopuses. In this experiment the octopuses learned to insert an arm into the maze and always send it in the same direction. The second sense tested was the sense of touch. In this experiment the octopuses learned that there is a smooth side in the maze and a rough side and that only one of the two will contain food. We observed that they learned to put an arm into the maze, 'feel' the area and then decide whether they had chosen the right side or needed to switch sides. It is worth noting that in this case the octopuses eventually chose slower search movements, which included exploring the interior of the maze. The results of the speed of learning are not significantly different from those found in previous studies", stated Dr. Gutnik.
The results of the study prove for the first time that the octopus's brain does receive sensory information from the arms and that from this information the octopus can deduce the position and movement of the arms. The study also shows for the first time that the brain can control the movement of the arm in real time even without the sense of sight, meaning that there is an exchange of sensory information from the arm to the brain at a high enough speed to make a decision about the continuation of the movement. In addition, among the important findings discovered in the study is that the octopuses do not always use the same arm, meaning that information learned with the help of one arm is available for use by another arm. From this it can be concluded that the information itself is not processed or stored at the level of the arm but in the central brain.
Dr. Gutnick concludes: "Our research makes it clear that although the octopus's arms have many autonomous movement and sensory capabilities, they are still an integral part of the octopus's ability as an organism to understand its environment and act on it, and when necessary they are under the control of the central nervous system. In addition, the research shows us that it is not an animal with nine brains, but an animal with one big brain and eight smart arms."
More of the topic in Hayadan:
