Researchers at the Hebrew University of Jerusalem have gained new insights into how the brain stores and recalls memory through a study on octopuses.
Dr. Benny Hochner, a neurobiologist who led the study at the Alexander Silberman Institute of Life Sciences, points out that octopuses and other related creatures, known as cephalopods, are considered to be the most intelligent invertebrates because they have relatively large brains, and can be trained for various learning and memory tasks.
The researcher even says that the behaviour repertoire and learning and memory ability of such creatures are comparable in their complexity to those of advanced vertebrates.
A previous study conduced by Hochner had shown that an area in the octopus, brain known to be important for learning and memory, showed a robust, activity-dependent, long-term synaptic potentiation (LTP) - a process which is strikingly similar to that discovered in vertebrate brains.
The LTP process accelerates the transformation of information between nerve cells by enhancing the transmission of electrical signals through a special structure called the synapse for days and even a lifetime.
Scientists believe that, in the brain region that stores memory, the synaptic connections between nerve cells that are more active during a specific learning function are strengthened by this activity-induced LTP.
Hochner says that this process can be described as an "engraving of memory traces" in the neuronal networks that store information for a long time.
In the current study, reported in the journal Current Biology, Hochner tested the same hypotheses and ideas in the brain of the octopus.
He blocked the ability of the brain to use LTP during learning by utilizing artificial LTP and electrical stimulation, shortly before training the subjects for a specific task.
The research team observed that, after the blocking of LTP, experimental group of octopuses did not remember well the task when tested for long-term memory the day after training.
The researchers obtained similar results when sensory information was prevented from getting into the learning and memory area by lesioning a specific connection in the brain.
Hochner says that the observations thus made supported the finding that LTP is indeed important for creating memories.
He says that the study's results suggest that the LTP process is an efficient mechanism for mediation of learning and memory, and shed new light on how memory systems are organized.
The researcher, however, admits that further research is required to determine how the LTP process is utilized in the brains of other animals and humans for storing memories, and how such memories are recollected.
According to him, his study shows that just like in humans, the short and long-term memory in the octopus are segregated into two separate systems, each in different locations in the brain.
Although the researchers have yet not discerned how the two systems might be interconnected, the organization of the octopus demonstrates a sophistication that was not described to date in other animals.
The short-term and long-term systems in the octopus are working in parallel, but not independently.
The researchers say that this is so because the long-term memory area, in addition to its capacity to store long-term memories, also regulates the rate at which the short-term memory system acquires short-term memories.
This regulatory mechanism is probably useful in cases where faster learning is significant for the octopus' survival in emergency or risky situations, they add.