Another component in the chain of actions that take place in the neurons, when the brain is in the process of forming memories has been identified by scientists at the University of Haifa.
The researchers say that, together with the results of previous studies, the new findings provide a better understanding of the process of memory formation and storage in the human brain.
In their study report, the researchers point out that the formation of memory to sensory information on the world-new sounds, tastes, sights, and smells-is vital for animal survival.
They say that very little of this information becomes short-term memory, and that only a small part of the information that becomes short-term memory ultimately becomes long-term and stabilized memory.
Previous studies led by Prof. Kobi Rosenblum found an elevation in the expression of the protein PSD-95 to be necessary for the formation of long-term memory.
The present study aimed to find out whether another molecular process - the addition of a phosphor molecule to the NMDA receptor protein (phosphorylation) - is necessary too.
Earlier studies have proven that changes in the NMDA receptor can adjust the neuronal network in the brain, and that during a learning process this receptor undergoes increased phosphorylation.
Before the present research, none of the studies had proved that the increase in phosphorylation of the NMDA is necessary for the process, and that the process would not occur without it.
During the current study, the scientists chose to focus on the formation of new taste memory in rats as a model for sensory memory because it could enable them to track when the process begins, its specific location is in the brain, and the molecular processes that occur during the process.
Verifying the findings of the previous studies, the first stage of the study showed that the new taste learning does indeed involve a process of increased phosphorylation in the NMDA receptors in the area specific to learning taste in the brain.
In order to do so, mature rats were trained to drink water at set times and after a few days some were given saccharine-sweetened water. The saccharine has no caloric value and therefore has no metabolic impact on the body and cannot affect the body's processes. As expected, the rats that received the newly sweet-tasting water and that began a process of learning, showed an increase in phosphorylation in comparison to those rats that continued drinking regular water.
The second stage of the study showed that obstruction of the phosphorylation process brought about a change in the location of the receptor in relation to the NMDA, and thus was likely to be responsible for inhibiting the formation of long-term memory.
"Our goal is to identify piece after piece of the complex puzzle that is the formation of long-term memory. Once we know how to describe the chain of actions that take place in the brain, we may be able to know where and how to interfere," said Dr. Dr. Liza Barki-Harrington, a member of the research team.
"The glutamate neural synapses - via the receptors of the NMDA - and dophamin, play a central role in a number of neural pathologies, including processes of addiction and of schizophrenia.
There is good reason to assume that one afflicted with schizophrenia has a sub- or over-functioning of this system, and its loss of balance is one of the causes of the illness. A better understanding of this balance - or loss of balance - in the normal processes will enable future discovery of new objectives for developing medications, which we hope will improve patients' lives significantly," added Prof. Rosenblum.
The study has been published in the Journal of Neuroscience.