Two studies, one with bees and one with mice, show that the brain can be manipulated into having a memory of an occurrence that did not in reality happen. Karen Hopkin reports

Have you ever sworn that you left your phone in the car, only to find it in your pocket, or on your desk or, admit it, in the fridge. Or maybe you just dreamed that you left it on the dashboard and the memory was so real you had to check there first. Well, it happens to the best of us. And, if you believe the latest research, it can happen to animals, too.

Okay, critters don’t misplace their electronic devices. But researchers are finding that memory can be as tricky for some beasties as it is for us. Take, for example, bees. These flying foragers are renowned for their ability to remember which flowers are best and where to find them. But it turns out bees can be bollixed.

Scientists trained bumblebees to expect a droplet of sugar water from two artificial flowers: one that was solid yellow, the other looking like an archery target of black and white rings. A few minutes later, the insects were allowed to choose between those two flowers and a third one that had yellow rings, a combo of the previous patterns. In this short-term test, the bees correctly showed a preference for the petals they’d seen had the sweet stuff.

But when challenged a few days later, the bees got bamboozled. They began selecting the yellow-ringed flower, even though it had never given them anything. It was like their memories had merged—or so conclude the authors in their paper in the journal Current Biology. [Kathryn L. Hunt and Lars Chittka, Merging of Long-Term Memories in an Insect]

Meanwhile, another team of researchers found they could manipulate the memories of mice while the animals slept. As rodents skitter from here to there, what are called “place cells” in their brains record their pathways and locations. These cells then replay these movements during sleep, helping the animals remember where they’ve been.

In this study, researchers used electrodes to turn on cells in the sleeping animals’ pleasure center at the same time as certain place cells lit up. This simultaneous sleepytime stimulation essentially forged an artificial memory, linking a particular location with good feelings. So when the mice woke up, they spent more time in the happy place of their dreams than anywhere else—even though nothing special actually happened there. This research is in the journal Nature Neuroscience. [Gaetan de Lavilléon et al, Explicit memory creation during sleep demonstrates a causal role of place cells in navigation]

Both studies suggest that we all may need to take our memories with a grain of salt. Or a dollop of nectar. Or a nice piece of cheese.

—Karen Hopkin

[The above text is a transcript of this podcast.]