New discoveries by Kiwi scientists could have implications for developing new therapies for brain disorders such as Parkinson's disease.
For nearly two decades, scientists have recognised how the timing of nerve impulses arriving at brain cells - in the order of one hundredth of a second - is critical to strengthening new connections while our new memories are formed.
But, at the same time, researchers have been confounded by the fact that the part of the brain that processes dopamine during the learning of a new skill appeared to follow completely the opposite timing rules to all other brain areas.
"In this case, it appeared that the brain cell needed to fire a nerve impulse before the actual movement activity was registered by the cell, which seemed intuitively wrong," explained Professor John Reynolds, of Otago University's Department of Anatomy.
Reynolds and Otago PhD graduate Dr Simon Fisher have now discovered that the pulse of dopamine into the brain that accompanies arrival of a reward had its own critical timing requirement, this time in the order of seconds.
When that requirement was met, the timing of nerve impulses in memory formation became exactly the same as all other brain areas.
"In other words, the naturally delayed arrival of these rewards shapes the ability for memories to be formed in a normal fashion," Reynolds said.
The researchers believe this finding had important implications for better understanding of and for developing new treatments for brain disorders such as Parkinson's disease and attention deficit hyperactivity disorder (ADHD), where the processing of brain reward was abnormal.
Further, since pulses of dopamine were released by pleasurable stimuli, such as chocolate or addictive substances like alcohol and nicotine and drugs of abuse, it also helped us understand how habits could be formed for ingesting these substances, Reynolds said.
The findings have been published in the international journal Nature Communications.