A new brain study reveals some new clues about the biological mechanisms involved in natural forgetting of long-term memory.
The study, by researchers at the University of Edinburgh in the UK, is published in The Journal of Neuroscience.
Senior author Dr. Oliver Hardt, of Edinburgh's Centre for Cognitive and Neural Systems, says:
"Our study looks at the biological processes that happen in the brain when we forget something."
Typically, the process of forgetting is seen as a failure of one or more basic memory functions such as acquisition, encoding, maintenance and retrieval.
However, in this latest study of rats, Dr. Hardt and colleagues suggest that forgetting may involve a well-organized process of active deletion rather than simply failure to remember.
They suggest their discovery could also help explain why some memories persist - such as those associated with traumatic events.
In previous work, the team showed that once encoded in the brain, memories are maintained by chemical signals between brain cells that use specialized signaling proteins known as AMPA receptors.
Brain cells communicate with each other through structures called synapses. The more AMPA receptors there are on the synapses, the stronger the memory, the researchers explain.
Blocking removal of AMPA receptors extended lifetime of memories
In their new study, Dr. Hardt and colleagues found that brain cells actively remove AMPA receptors from their synapses. Thus, over time, the memory fades as the AMPA receptors gradually fall in number.
The researchers tested this by blocking the removal of the AMPA receptors. They used a drug that keeps them on the synaptic surfaces of the cells. They note:
"We found that blocking their synaptic removal after long-term memory formation extended the natural lifetime of several forms of memory."
They conclude that this decay-like forgetting process, depending on the memory removed, may play an important role in shaping animals' behavior in response to their environment.
Researchers are already studying drugs that block AMPA receptor removal as a possible treatment for memory loss in Alzheimer's and other forms of dementia.
The team suggests further studies should now be done to investigate how blocking AMPA removal might affect the ability to acquire and retrieve memories.
Dr. Hardt says there is also a need to find out why some memories persist, while others are erased. He concludes:
"If we can understand how these memories are protected, it could one day lead to new therapies that stop or slow pathological memory loss."
The study follows other recently published work by Pennsylvania State University researchers, where Medical News Today learned that memory encoding may be influenced by expectation.