A new study that was published in the journal Nature Communications shows that rats have better episodic memories than previously believed. Based on prior research, it was assumed that they could only remember two or three events with context. The research team’s new findings show that they can remember over 30 memory events.
Episodic memories are memories in which the individual can remember the context. Rather than simply remembering a familiar face, for example, episodic memory allows a person to also remember where they last met the person, what they were doing, and how long ago they met. While episodic memory has been studied in humans, there’s been less research conducted with animals. Rats and other laboratory rodents were generally considered to have weak episodic memories but there was no formal research to back this up.
A team of researchers from Indiana University exposed laboratory rats to a total of sixteen unique odors, including basil, strawberry, and blueberry. All of the odors were scents that were brand new to the rats. First, the researchers trained the rats to associate new odors with food rewards. The rats were then moved to colored “arenas” where they were exposed to the same scents again. After, the rats were moved to a second arena where they were exposed to two scents at the same time. They were then moved back to the original arena with two scents and had to choose the one that was “new” for that particular arena. As an example, the rats may have been exposed to a basil scent in one arena. Then they were moved to a brand new area and exposed to a combination of basil and strawberry. Once moved back to the original arena, the rats were exposed to basil and strawberry again. The correct choice would be the strawberry odor since that scent was new to that particular context, even though they had smelled it previously in a separate arena.
The rats were highly accurate in these trials and had no problem selecting the scent that was new for a specific arena. The researchers found that they could remember 30 or more events of this type, showing an excellent episodic memory compared to previous beliefs about rodent memories.
The findings show that rats have better episodic memories than researchers previously thought. This may make rats viable models for studying human cognition and memory.
Panoz-Brown et al. Rats Remember Items in Context Using Episodic Memory. Current Biology (2016).