LAWRENCE — Recent studies on rats and mice — the first such on non-human animals — could have an important influence on how we think about the nature of memory, a University of Kansas philosopher said.
Using a technique called optogenetics in non-human animals, neuroscientists and psychologists discover how human memory works by studying false memories. A traditional way of thinking about memory presumes that the mind tends to work like a Rolodex, where information is stored and retrieved when it's needed.
The job of memory is to keep a record of each past experience. Studies of false memory have led many scientists and philosophers to think that this view is mistaken and that memory does not keep records of our past experiences at all.
"Instead, 'memories' of past events are just images we generate as needed when we are trying to remember," said Sarah Robins, assistant professor of philosophy and author of two recent journal articles on the mechanisms of false memory.
Robins said the right answer might be somewhere in the middle. Deciding between these views of memory has been difficult because it's only been possible to study false memories in humans. This restricts the available evidence to behavioral and neuroimaging studies.
"Knowing which view of memory is right will likely require in depth-investigation of the brain mechanisms that support false memory, and such studies can only be done in non-human animals," she said. "And because no one knew how to create false memories in non-human animals, it seemed there was no way to move forward."
However, Optogenetics has changed this. Optogenetics is an exciting new intervention technique by which neurons are altered to become responsive to light.
"It’s exciting for memory researchers because its use in studies of rodent — such as rats or mice — memory has produced the first example of false memories in non-humans," she said.
In her recent essays, "Optogenetics and the Mechanism of False Memory" in the journal Synthese and "Representing the Past: Memory Traces and the Causal Theory of Memory" in Philosophical Studies, Robins argues that these findings suggest two things: First, false memories are a result of an interaction between the brain's memory trace and additional, misleading information; and second, that there are mechanistic differences in the production of successful memories and various kinds of memory errors.
Optogenetics allows researchers to keep track of which neurons rats use to encode a memory and then later re-activate these neurons with light.
"It is a way of turning a memory back on without putting the animal back in its original context," Robins said.
This allows researchers to apply various techniques to distort the memory–changing the rat’s memory of a previous experience from positive to negative or vice versa. The result is a false memory: rats who remember being in particular contexts but now think their experience there was good instead of bad, or bad instead of good.
The understanding of the brain mechanisms of false memory that these studies provide supports a hybrid, middle-ground view between traditional and newer constructive views of memory, Robins said.
Gaining support for this theoretical view of how memory works may have some important applications.
"The broader implication is that by learning more about what distorts things and how factors such as mood can distort in these ways or asking leading questions can distort things in other ways, then we can know how likely people's memories are to be reliable in certain situations," she said.
This approach could help assess the credibility of eyewitness testimony in court, Robins said. Or it could be helpful to medical professionals if they are able to distinguish between dementia patient who have lost memories and those who have simply lost the ability to access their memories.
"Knowing that difference is really helpful for knowing who could be put into different levels of independent living situations," Robins said.