January 20, 2021

Transient forgetting' controlled by dopamine circuits, scientists find Memory-retrieval block revealed; pauses thought without abolishing long-term memories.

January 20, 2021

JUPITER, FL In a landmark neurobiology study, scientists from Scripps Research have discovered a memory gating system that employs the neurotransmitter dopamine to direct transient forgetting, a temporary lapse of memory which spontaneously returns.

The study adds a new pin to scientists' evolving map of how learning, memory and active forgetting work, says Scripps Research Neuroscience Professor Ron Davis, PhD.

This is the first time a mechanism has been discovered for transient memory lapse, Davis says. There's every reason to believe, because of conservation biology, that a similar mechanism exists in humans as well.

The study, Dopamine-based mechanism for transient forgetting, appears Wednesday in the journal Nature.

Everyone has experienced transient forgetting. A name sits on the tip of our tongue, but resurfaces only after a meeting. We walk into a room and forget why we entered until we leave. Annoying, to be sure. But does it represent a mental glitch, or is absentmindedness a feature of a normal brain? Was the elusive memory erased and somehow restored, or merely hidden for a time? Exactly how transient forgetting worked was unknown until now.

To derive an answer, Davis' team worked in the common fruit fly, a model favored by neurobiologists for decades due to its relatively simple brain structure, ease of study and translatability to more complex animals.

The team put their flies through a series of training exercises, teaching them to associate an odor with an unpleasant foot shock. They then watched as several interfering stimuli, such as a blue light or a puff of air, distracted the flies so they forgot the odor's negative association, temporarily. Interestingly, stronger stimulation led to longer lasting periods of forgetting.

Additional biochemical studies revealed a single pair of dopamine-releasing neurons in the flies, called PPL1- 2 '2, which directed the transient forgetting. Dopamine sent from other neurons didn't have the same effect. The neurons activated dopamine receptors called DAMB on axons extending from neurons in the memory-processing center of the fruit fly brain, called its mushroom body.

Martin Sabandal is a graduate student in the lab of Neuroscientist Ron Davis, PhD, at Scripps Research in Jupiter, Florida.

LINK:	https://www.scripps.edu/news-and-events/press-room/2021/20210120-davis...
	See more stories from scripps

Most recent headlines