Humans and insects have navigation skills that are even better. We decided to freeze some ants and beetles to learn more about how they remember their way home after an ant bite.
Their skills are impressive. The ants living in the salt pans can travel for more than a kilometer, knowing their location at all times. There are no landmarks or other features in that terrain to help the ants recognize where they are.
The ants use the Sun's position on the sky as a compass and their own motion to estimate distances. You can point a line back to it if you know the direction and distance you walked away from home. The ants can return home after finding food.
Consider that 1 kilometer is 100,000 times the length of an ant. It's like a human walking from New York to Washington, DC, and then back, knowing at all times the correct direction and how far they have to go.
We wanted to know how they do it.
Scientists have been able to make brain cells emit different colors of light thanks to recent developments.
Researchers were able to untangle how the brain's neural spaghetti connects to each other thanks to this huge achievement.
The technique has been used to see how an insect's brain keeps track of its direction while it moves.
Its brain can calculate how far it has traveled with the information it has.
The direction and distance traveled by the insect are determined by what is in the brain of the insect. How is this stored so they can find their way back?
It was quite a puzzle. The insects need to remember direction and distance constantly on the fly, but they can remember it for several days.
The two aspects of memory that are incompatible are fast updating and long lasting.
We decided that freezing insects was the best way to find out how insects remember over a long period of time.
Let me explain why it sounds strange.
When someone goes under anesthesia, they forget certain things, but remember others, depending on how their memories are stored.
cooling insects down is the closest thing to anesthesia. The insects fall into a coma when their temperature is reduced to melting ice temperature.
If their direction and distance memories are maintained as short-term electrical activity, they will be wiped out when they are frozen, but if they are stored in synapses between neurons, they will be maintained.
We took ants and beetles away from their nest and cooled them down for 30 minutes. After they recovered, we released them at an unfamiliar place to see what they would do.
When these insects are released at an unfamiliar place in their home environment, they would run towards where their nest would have been had they not been displaced.
They would run parallel to their normal path, and once they have traveled the expected distance they would start searching for their nest.
The insects that had been frozen moved in the expected direction, but forgot the distance they should travel, so they started searching for the entrance to their nest too early.
It was initially puzzling that the distance memory deteriorated while the direction memory was preserved, but this result did not produce a clear-cut distinction between short-term and long-term memory that we had expected.
The best explanation for the phenomenon is that there is one common memory that contains both the direction and distance, and that it decays when frozen.
We think it works.
Imagine if you could remember your position in x-y coordinates instead of remembering a distance and a direction.
If you lose some of your memory, both your x and y values will be reduced, and you will end up with a shorter distance, but still the same angle.
It seems that insects have been using coordinate systems for a long time. How cool is that?
We all need to return to our homes. Learning how insect brains remember will help us understand how humans do it.
The University of Edinburgh has a PhD Candidate in Computational Neuroscience and BioRobotics, as well as a Senior Lecturer in School of Natural Sciences and a Post-doc in Functional Zoology.
This article is free to use under a Creative Commons license. The original article is worth a read.
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