Animals can mentally replay past events: study

Scientists have found the first evidence that animals can mentally replay past events from memory, a discovery that could help develop new drugs to treat Alzheimer's disease.

"The reason we are interested in animal memory is not only to understand animals, but rather to develop new models of memory that match up with the types of memory impaired in human diseases such as Alzheimer's disease," said Jonathon Crystal, a professor at Indiana University in the US.

Most preclinical studies on potential new Alzheimer's drugs examine how these compounds affect spatial memory, one of the easiest types of memory to assess in animals, said Crystal, who led the study published in the journal Current Biology.

However, spatial memory is not the type of memory whose loss causes the most debilitating effects of Alzheimer's disease.

"We are interested in episodic memory - and episodic memory replay - because it declines in Alzheimer's disease, and in aging in general," said Danielle Panoz-Brown, a PhD. student at Indiana University.

Episodic memory is the ability to remember specific events. For example, if a person loses their car keys, they might try to recall every single step - or "episode" - in their trip from the car to their current location.

The ability to replay these events in order is known as "episodic memory replay."