Ants store long- and short-term memories on different sides of their brains

The left and right sides of our brains store different kinds of memories: The left side specializes in verbal information, for example, whereas the right side specializes in visual information. But it turns out we’re not the only ones. A new study suggests ants—like humans, songbirds, and zebrafish—also store different memories in different sides of their tiny brains, in a process called lateralization.

Honey bees and bumble bees seem to exhibit lateralization when it comes to memories involving scent. But researchers wanted to know whether other insects were also dividing up the labor of their brains. They trained wood ants (Formica rufa) just as Russian physiologist Ivan Pavlov trained his famous dogs—by treating them with food each time they received a certain signal.

To find out whether ants stored visual memories in different parts of their brains, the researchers touched the right antenna, the left antenna, or both of dozens of ants with a sugary droplet each time they looked at a blue object (above). Then, the researchers tested their memories 10 minutes, 1 hour, and 24 hours after the training. They did this by showing them the blue object and observing whether they extended their mouths, a “thirst” response similar to Pavlov’s dogs salivating.

Ants trained with the right antenna had strong thirst responses at the 10-minute mark and lingering responses after 1 hour, but not after that. Ants trained with the left antenna had no response at 10 minutes or 1 hour, but appeared thirsty 24 hours after their training. That suggests one side of the ant brain stores short-term memories, whereas the other side stores longer term ones, the researchers write today in the Proceedings of the Royal Society B.

This is the first evidence that short- and long-term visual memories are stored in different sides of insect brains, the researchers say, a feature that might help them save energy and memory storage capacity in the tiny organs.