Learning and memory, between octopuses and humans and other mammals
An octopus is a mollusk from the invertebrate family and almost its entire body is made of soft tissues. That is, he has no skeleton (joints and bones) but only muscles. It is endowed with flexibility, motor skills and great freedom of movement and is able to perform complex actions such as swimming, crawling, walking and leaping towards prey. In addition, he is endowed with a specially developed brain in relation to molluscs and invertebrates that allows him to effectively control these actions. It is not without reason that it is considered a fascinating research object that also has practical implications.What is the question? How do octopuses learn and remember? And is their nervous system, which is responsible for learning and memory similar to that of mammals?
Prof. (Emeritus) Benjamin Hochner from the Institute of Life Sciences at the Hebrew University of Jerusalem, researches several aspects of octopuses; One of them is the movement control in the flexible arms of the octopus as a basis for designing robots that are built from flexible materials; His goal is to develop robots that resemble octopuses in terms of the flexibility of their arms (having infinite sliding possibilities). According to him, "Such robots will be able to function in areas with an unknown structure, such as disaster areas (for example, an earthquake and a ship that has sunk). The goal is to program them so that they can adapt their body structure to the action required at that moment, in real time, and carry it out through a series of similar movements to octopuses".
Stand on the four back arms and send the four front arms towards the target
The challenge in designing such robots, as Prof. Hochner explains, is in the control of movement: "The nervous system of the octopus has to control endless degrees of freedom of movement (for example up-down, right-left, forward-backward) so that they do not get out of control, and we are researching how It does this. We found that the octopus uses predetermined movements. For example, if it wants to reach out to a target, it creates a bend at its base and then rolls it (an operation that includes control of only three degrees of freedom)".
The octopus is also considered a particularly intelligent and curious animal, from whose mind you can learn basic biological principles in the processes of learning, memory and information processing. Therefore, in Prof. Hochner's latest research, which was done in collaboration with Dr. Nir Nesher and Dr. Tal Shamrat from the Rupin Academic Center, the vertical lobe in octopuses was examined - the brain area responsible for learning and memory processes in them. Prof. Hochner says: "The learning and memory abilities of the octopus are amazing (as demonstrated in nature and in the laboratory), and we are trying to understand if the systems that mediate them are similar to those that evolved in vertebrates like us or are based on other mechanisms."
In a series of experiments, the scientists discovered that the electrical activity in the vertical lobe in the octopus brain is similar to that which takes place in the hippocampus - a brain area involved in learning and memory processes in mammals. In addition, they discovered that, as in the hippocampus, long-term synaptic amplification can also exist in the vertical lobe in octopuses; This is a brain phenomenon that is considered the neural basis for memory, in which the connection between nerve cells (neurons) is strengthened after repeated activation of the synaptic connection and remains so for a long time. "After we strongly stimulated a group of neurons in the vertical lobe, we saw that the strength of the electric field became stronger and remained so for several hours. A similar phenomenon also occurs in humans (for example during memorization) and other mammals, and it helps them learn and remember in the long term," explains Prof. Hochner.
In the next step, the researchers wanted to check if the molecular (biochemical) mechanism that is responsible for the long-term synaptic amplification is similar to the one that exists in mammals. To this end, they conducted pharmacological experiments in which they blocked different molecules to check which of them is involved in the phenomenon. When they blocked the molecule NO (nitric oxide) - which plays a role in dilating blood vessels and controlling blood pressure in mammals and is known to be associated with learning processes in invertebrates and vertebrates - the phenomenon was stopped. In other words, the strength of the interneuronal connection became weaker and weaker. From this the researchers concluded that NO is the molecule that mediates long-term synaptic amplification in octopuses. This, in contrast to mammals, where other molecules are responsible for this. Prof. Hochner: "This finding indicates that the molecular mechanism that mediates learning and memory in octopuses developed separately from that of mammals and its effectiveness is wonderful. From an applied point of view, it is a fairly simple mechanism and it may be possible in the future to insert it into the genes of the nervous system (using gene editing technology), thus correcting vulnerabilities related to learning and memory".
Later - with the help of a research grant from the National Science Foundation - the researchers plan to test how electrical stimulation of neurons causes the activation of the enzyme that produces NO and how the synaptic strengthening can last for a long time. "It is possible that NO itself causes this. That is, that the enzyme continues to work as long as it is around. This is a unique mechanism that we want to prove in octopuses. To this end, we will perform biological-molecular and biochemical experiments in which we will isolate the enzyme and test its properties," Prof. Hochner concludes.
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