Memory loss is love’s great thief. Those who suffer aren’t just the ones who can’t remember. Family, friends and loved ones agonize over how to react when the disorder begins its often inexorable progress.
Research from scientists at UGA is offering new insights into how one kind of memory works. The study, published in the online edition of The Proceedings of the
National Academy of Sciences, shows that laboratory rats have “episodic-like memory” and could open novel ways to study life-robbing loss of memory in humans.
“This research shows that rats remember the time at which they encounter a distinctive event, in addition to what the event was and where it happened,” said Jonathon Crystal, an associate professor in the department
of psychology’s Neuroscience and Behavior Program in the Franklin College of Arts and Sciences. “These experiments provide insight into the memory system that retains the time of occurrence of earlier events.”
Co-author of the paper was Wenyi Zhou, a doctoral student in Crystal’s laboratory. The work was supported by a grant from the National Institute of Mental Health.
Memory loss in humans can be caused by an array of diseases, such as Parkinson’s and Huntington’s, but the great destroyer of memory is Alzheimer’s disease, which is progressive and so far irreversible. Drugs used to treat cancer can cause memory loss, as can certain forms of mental illness or traumatic brain injuries. Memory loss often ends an independent life for those who suffer it, and researchers around the world are looking for ways to slow or stop damage to memory, especially through pharmaceuticals.
Still, much remains unknown about the disorder, and so having an effective animal model of memory will be critical to understanding how and why memory fades.
The paper deals with one specific kind: “episodic memory,” in which unique past events are recalled and can be placed in time and at a specific location. For years many scientists believed that only humans had episodic memory, and that supposition may have limited approaches to studying the problem.
Crystal argues in this PNAS paper, that behavioral experiments can show that rats do have such memory. If confirmed, the implications are considerable because episodic memory would give researchers a way to study this type of memory in a nonhuman model.
“It has been argued that retrieval of episodic memories is analogous to traveling back in time,” he said. “Recent studies with nonhuman animals suggest that animals remember specific episodes from their past, but there has been controversy over whether episodic-like memory in rodents is the same as it is in humans.”
The experiment reported involved setting up a situation in which rats were “asked” to remember the time of day at which they encountered a distinctive event, in addition to what occurred and where it happened. The event was the feeding of chocolate-flavored pellets-chocolate being a flavor that rats crave.
The rats were fed in the morning and afternoon on separate days, but chocolate was available at only one time and place. Rats adjusted their revisits to the chocolate location by using the time of day rather than how long ago the event occurred.
“Our results suggest that at the time of memory assessment, rats remember when a recent episode occurred, similar to human episodic memory,” said Crystal.
