The findings in mice could have implications for Parkinson’s disease patients, who often struggle with simple tasks early in the disease, and for bad habits such as addictions, said Dr. Joe Z. Tsien, a neuroscientist and co-director of the Brain and Behavior Discovery Institute at GHSU.
In findings published in the journal Neuron, Tsien studied mice that had been specially bred to lack the NMDA receptor on dopamine-producing neurons in the mid-brain region. The mice were then subjected to memory tasks, including finding their way through a maze and getting a food pellet by pulling down a lever.
The mice could all learn to respond to the task but mice that lacked the key receptor failed to form the kind of automatic response that the other mice showed. For instance, in the maze test, normal mice automatically took a right turn out of one end of the maze to send them on the correct path, but mice that lacked the key receptor appeared to search for cues to show them the way. After a brief interval, normal mice remembered to pull on the lever to get food when hungry, but mice that lacked the receptor struggled.
This type of memory formation has not received the same kind of research attention others have, but it is important, Tsien said.
“It minimizes or reduces your cognitive load,” he said. “You can focus your mind on something more important.”
The findings could have implications for Parkinson’s, where patients also begin to miss dopamine-producing neurons and who also can struggle with learned tasks, like tying shoes.
“There’s a lot of clinical implications,” he said. “Dopamine is important somehow for maintaining a habit.”
Tsien and colleagues have previously published a study implicating the receptor-bearing neurons in forming a nicotine habit and that could have some bearing on addiction and treatment, Tsien said.
“Addictive behavior is a habit,” he said. “That is why it is harder to get rid of because a habit kicks in and you are doing it subconsciously. If you begin to understand and know more about the molecular basis of habit formation, then it puts you in a better position to work on the mechanism or means of how to get rid of the habit.”