Rather than wiping out our memories, new research out of Columbia University suggests that dementia instead confuses the brain about which neurons store which memories, thereby making those memories harder to recall. In other words, the memories might remain—however deeply hidden—in the brain, and thus accessing them is just a matter of stimulating the right neurons. "It has the potential to lead to novel drug development to help with regaining memories," a researcher tells the Washington Post. To study this, researchers used a laser technology called optogenetics to watch neuron activity in the brains of mice. All mice in this study were given an electric shock after sniffing a lemon scent, but a week later, only half those with dementia froze when they smelled lemon in anticipation of being shocked, compared to all the healthy mice freezing.
The researchers were able to watch the healthy mice retrieve memories from the same place where they'd been stored, while mice with dementia called up other memories stored elsewhere. But by stimulating the neurons with a blue laser, scientists were able to reactivate memories in the mice with dementia. The downside? Optogenetics isn't ready for humans, notes the Post, "because it isn’t yet safe or practical to tinker with our neurons or stick lasers into our brains." Next up, scientists hope to see whether memories are stored and retrieved similarly in humans. The Independent points out that in some Alzheimer's cases, music has been known to rouse old memories, "suggesting they may not disappear completely." (Diagnosis of dementia is improving, but treatment remains elusive.)