The octopus has a relatively large brain, and can be trained for various learning and memory tasks.Research into the octopus has shed new light on how our brains store and recall memory, according to Israeli researchers.

The discovery, by Dr. Benny Hochner of the Department of Neurobiology at the Hebrew University of Jerusalem, shows that long-term synaptic potentiation (LTP), a process that accelerates the transformation of information between nerve cells by enhancing the transmission of electrical signals through a special structure called the synapse, has a vital role in creating both short-term and long-term memories.

Dr. Hochner has been working with octopuses and related creatures, known as cephalopods, for some years. The octopus is considered to be one of the most intelligent invertebrates because it has a relatively large brain and can be trained for various learning and memory tasks, says Hochner.

The behavior repertoire and learning and memory abilities of the octopus are comparable in complexity to those of advanced vertebrates. At the same time, however, they are still invertebrate mollusks with brains that contain fewer nerve cells and much simpler anatomical organization than that of vertebrate brains.

In a previous study, Hochner discovered that an area in the octopus brain, known to be important for learning and memory, showed a robust, activity-dependent, LTP – a process which is strikingly similar to that discovered in vertebrate brains.

Scientists believed that in the area of the brain that stores memories, the synaptic connections between nerve cells active during a specific learning function are strengthened by this activity-induced LTP. Hochner describes this process as an “engraving of memory traces” in the neuronal networks that store information for a long time.

In his new research, Hochner tested these ideas, by blocking the ability of the octopus to use LTP during learning, by using artificial LTP and though electrical stimulation.

He discovered that when LTP was blocked shortly before training for a specific task, the experimental group of octopuses did not remember the task well when tested for long-term memory the next day.

Similar results were obtained when sensory information was prevented from getting into the learning and memory area by lesioning a specific connection in the brain.

These results, published recently in the journal, Current Biology, support the finding that LTP is indeed important for creating memories and suggests that the LTP process is an efficient mechanism for mediation of learning and memory.

The research also helps clarify how memory and learning systems are organized, says Hochner. Scientists have already documented how memory processes can be divided into a short-term memory of minutes or a few hours, and long-term memory that can store important events and facts for days or even an entire lifetime.

Hochner’s results show that as in mammals, including humans, the short and long-term memory in the octopus are segregated into two separate systems, each in different locations in the brain.

Hochner stresses that further research is necessary to understand how this cellular process is used in other animal or human brains for storing memories, and how these memories are recollected.