February 27, 2013
Rat Memory Study Could Open The Door To Treat Alzheimer’s Disease
Brett Smith for redOrbit.com - Your Universe Online
Researchers from Indiana University have found that rats have a capacity for “source memory,” a finding that could have implications for both future animal studies and the treatment of human memory disorders.
According to the IU team´s report in Current Biology, a rat is capable of remembering how it got a certain food reward.
"Researchers can now study in animals what was once thought an exclusively human domain," said co-author Jonathon Crystal, a professor in the Department of Psychological and Brain Sciences at the IU. "If you can export types of behaviors such as source memory failures to transgenic animal models, you have the ability to produce preclinical models for the treatment of diseases such as Alzheimer's."
Source memory allows us to remember a source of information we once received. If you have somehow ever had all the answers during a game of trivia, but can´t remember how you came to learn those facts: it´s an example of source memory failure.
The results of the study are somewhat groundbreaking, especially since source memory has long been considered a unique human ability. The human mind uses source information to construct memories of distinct events or episodes.
On the other hand, animals have long been thought to use other types of memory, based on conditioning, to perform tasks.
Crystal noted that another trait shared by both humans and rats led to the study´s findings — the love of chocolate.
"There's no amount of chocolate you can give to a rat which will stop it from eating more chocolate," he said.
The IU researchers used a series of experiments to see if the rats in their laboratory had source memory capabilities. In each experiment, the rats foraged for food that was or was not replenished at a specific location. In order to predict food replenishment, the rats needed to remember how they had come across a piece of chocolate, whether they were placed near the trough containing the chocolate or had to run to get it.
Using different mazes to rule out potential conditioning, the researchers were able to base their findings on three different lines of evidence. First, they found that the rats were able to adjust and locate the chocolate based on previous memories of finding the reward. Second, they disassociated source memory from a reward´s location memory by finding that the rats´ capacity to remember lasted more than a week. Third, the researchers temporarily inactivated the CA3 region of the hippocampus, an area of the brain thought to be crucial for accurate source memory — resulting in an inability to find the chocolate reward.
"What we're trying to do is to develop behavioral approaches with rodents that tap into those types of memory systems," Crystal said. "This study is the demonstration, the proof of the concept that source memory exists in animals. But the mechanism that supports it is open. We're now interested in working out the sub-areas of the hippocampus that are involved in episodic memory, testing hypotheses about different regions being involved in short-term and long-term episodic memory, working out the neuroanatomical pathways."