Neuroscientists Have Pinpointed Mechanism For Forming Memories

When we think about memory it is in terms of saving information so we can pull it back when we need it. Most of us don’t think of how important memory is to our well-being and mental health. Imagine if you were to forget how to walk, or talk, or do simple tasks -that all requires memory.

Although some forgetting is normal, how we forget is poorly understood. Scientists from the Florida campus of The Scripps Research Institute believe they have pinpointed a mechanism that could be essential in the forming of initial memories, and equally important in getting rid of them after the memories have formed. The study was published in the May 10, 2012 edition of the journal Neuron.

Ron Davis, chair of the Scripps Research Department of Neuroscience who led the project said, “This study focuses on the molecular biology of active forgetting. Until now, the basic thought has been that forgetting is mostly a passive process. Our findings make clear that forgetting is an active process that is probably regulated.”

In order to better understand the mechanisms involved in forgetting, Davis and his colleagues studied fruit flies (Drosophila). Fruit flies are a key model found to be highly applicable to humans in the study of memory. The flies were placed into situations that associated certain smells with positive reinforcement, like food, or negative reinforcement, like a mild electrical shock. Changes were then observed in the flies’ brains as they forget or remember information.

They found that a small subset of dopamine neurons actively regulate the acquisition and forgetting of memories after learning, using a pair of dopamine receptors in the brain. Dopamine, a neurotransmitter, plays an important role in a variety of different processes, including reward and punishment, memory, learning and cognition.

What would cause a single neurotransmitter to have two quite opposite roles in both the forming and eliminating of memories?

They believe that when a new memory is first formed, there also exists an active, dopamine-based forgetting mechanism that begins to erase memories unless some importance is attached to them. This process is known as consolidation, and it may shield important memories from the dopamine-driven forgetting process.

The indicators show that specific neurons in the brain release dopamine to two different receptors known as dDA1 and DAMB. These are located on what are called mushroom bodies (because of their shape). These densely packed networks of neurons are vital for memory and learning in insects. The dDA1 receptor is responsible for memory acquisition, while DAMB is required for forgetting.

When dopamine neurons begin the signaling process it over stimulates the dDA1 receptor and begins to form memories, an essential part of memory acquisition. Once that memory is attained, however, these same dopamine neurons continue signaling, except this time the signal goes through the DAMB receptor, which triggers forgetting of those recently acquired, but not yet consolidated, memories.

A graduate student in the Davis lab, Jacob Berry, who led the experimentation, showed that inhibiting the dopamine signaling after learning enhanced the flies’ memory, and by hyperactivating those same neurons after learning the memory is erased. In addition, a mutation in one of the dDA1 receptors produced flies unable to learn, while a mutation in the DAMB, blocked forgetting.

While Davis was surprised by the mechanisms the study uncovered, he was not surprised that forgetting is an active process. “Biology isn’t designed to do things in a passive way,” he said. “There are active pathways for constructing things, and active ones for degrading things. Why should forgetting be any different?”

Davis added that this study also brings into a focus a lot of fascinating issues, like savant syndrome, for example. “Savants have a high capacity for memory in some specialized areas,” he said. “But maybe it isn’t memory that gives them this capacity, maybe they have a bad forgetting mechanism. This also might be a strategy for developing drugs to promote cognition and memory–what about drugs that inhibit forgetting as cognitive enhancers?”

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About the author:

Ron White is a two-time U.S.A. Memory Champion and memory training expert. As a memory keynote speaker he travels the world to speak before large groups or small company seminars, demonstrating his memory skills and teaching others how to improve their memory, and how important a good memory is in all phases of your life.


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