New learning pathway could lead to Alzheimer’s cure

Australian and US researchers have shown that the brain uses a different set of physiological tools to form memories for the first time than it uses for subsequent learning of similar information.

The findings are expected to turn conventional wisdom regarding diseases such as Alzheimer’s on its head, whilst paving the way for exciting new treatments for it and other conditions where memory is impaired.

Memories are formed in a horn-shaped part of the brain called the hippocampus, courtesy of a small protein called ‘NMDA receptor’. This receptor allows calcium to enter neurons thereby setting off a chain of molecular reactions that help encode experience and consolidate memory.

Learning experts generally agree that all memories are formed in this manner. However, researchers at Sydney’s Garvan Institute and the University of California Los Angeles (UCLA) have found that NMDA receptors are not required for the learning of tasks or information similar to that which has already been absorbed. Rather, it appears that a new class of receptors, also calcium permeable, take on the job following the initial ‘first learning’.

“When we started this research, we knew that the NMDA receptor was implicated in learning and memory, and we decided to see if we could mimic its process through another receptor system,” said Dr Bryce Vissel, a molecular neuroscientist from Sydney’s Garvan Institute, who worked on the study.

“Instead of having to create a new receptor system, we discovered one already in existence – one that was NMDA-independent. This amounted to uncovering a whole new mechanism of learning.”

Vissel worked for the past six years with learning theorist Dr Michael Fanselow and electrophysiologist Dr Thomas O’Dell, both from UCLA.

“The system we’re working with is one that we know is critically involved in Alzheimer’s disease and other kinds of brain deficit memory impairment,” Fanselow said.

“This is just the start – we have uncovered a mechanism that contributes to learning and memory, and we now have to figure out what to do with it.”

The next stage will be to answer important questions such as when is the mechanism important normally, also can it be used to have some protective effect in conditions like Alzheimer’s disease, where neurons are dying, for instance by stimulating these pathways to maintain their role in memory.

“We can see that we might now have a target for drugs that are different from the standard class of cognitive enhancers,” Fanselow said.

“We can also see the possibilities for different styles of training that better activate this newly discovered mechanism.”

The study was reported this week in the journal Plos ONE