Undoubtedly, our ability to create and retrieve memories is a fundamental part of the human experience, but we still have much to learn about this process. For example, today, scientists lack a clear understanding of how the interaction of different areas of the brain for the formation and retrieval of memories. However, the results of recent studies shed light on this phenomenon, showing how is the neural activity in two separate brain regions during the retrieval of memories in the hippocampus and neocortex. The paper was published in the journal PNAS (Proceedings of the National Academy of Sciences).
As the hippocampus and the neocortex, helping to retrieve memories
The hippocampus, a structure located deep in the brain, has long been considered the centre of memory. The hippocampus helps “glue” the fragments of memories (“where” and “when”), providing a collaboration of neurons. This is often called “neural synchronization”. When the neurons that encode information of the “where” is synchronized with the neurons that encode the information of “when”, these items become linked through the phenomenon known as the “theory of Hebbian”. But the hippocampus is just too little to store each individual item memory. This has led researchers to the theory that connects the hippocampus to the neocortex — the area of the brain that processes complex sensory details such as sound and sight — to help fill in the details of memories.
However, the work of the neocortex is the antithesis to the work of the hippocampus, the neocortex, ensures that the neurons will not work together. Researchers call this “neural desynchronization”. Imagine you ask 100 people to name their names. Obviously, the synchronicity of their response to make recognition of each individual name is not possible. But if every person desynchronize your answer (that is, people will take turns to pronounce their names), you probably will gather from them much more information. The same applies to neurocortical neurons — if they are synchronized, then struggling to convey the message, but if they desynchronizers, information is easily transmitted.
The researchers ‘ work showed that the hippocampus and the neocortex are really working together, when talking about memories and their retrieval. Hippocampus sinhroniziruete its activities with the neocortex to glue the parts of the memories, and the neocortex later helps them out. Meanwhile, the neocortex desynchronize its activities to help process the event information and later retrieve memories.
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In the study, researchers tested 12 patients with epilepsy aged 24 to 53 years. All subjects had electrodes placed directly into the tissue of the brain — the hippocampus and the neocortex, as this is part of the treatment of epilepsy. During the experiment, patients studied associations between different stimuli (such as words, sounds, and video), and then recalled them. So, the scientists found that during training, the neural activity in the neocortex desynchronized, and then, after about 150 milliseconds of neural activity in the hippocampus is synchronized. Apparently, information about the sensory detail of the stimulus is first processed by the neocortex, and then passed to the hippocampus for gluing. The researchers found that the hippocampus and the neocortex, are closely cooperating in the formation and recovery of memories.