For most of us, finding the way is not a particularly difficult thing. We humans are excellent navigators who can cope well in different environments. But the navigation skills of insects may be better than ours, or even quite amazing. For example, ants living in the salt fields of the Sahara can travel more than a thousand meters and know the relationship between them and their nests at any time during the journey.
For most of us, finding the way is not a particularly difficult thing. We humans are excellent navigators who can cope well in different environments.
But the navigation skills of insects may be better than ours, or even quite amazing.
For example, ants living in the salt fields of the Sahara can travel more than a thousand meters and know the relationship between them and their nests at any time during the journey.
On this terrain, there are no landmarks or other features that help ants identify their location.
Don't forget that a kilometer is about 120000 times the length of an ant.
This is equivalent to a person walking from Hangzhou to Shanghai without using any landmarks to know the right direction and distance at any time along the way.
For many insects, finding the right direction is almost a matter of life and death.
Like great human explorers such as Columbus and Magellan, ants know how to use the position of the sun in the sky as a compass and estimate their distance by their own motion.
This ensures that the ants return to the nest accurately after foraging.
When an insect leaves the nest, its direction and distance are encoded by neurons in the brain.
A team of scientists conducted a very special experiment to explore exactly how insect brains encode and store these location-related memories.
They frozen some ants and beetles (don't worry, the little ones are still alive).
The study suggests that insects may "use" a system similar to the Cartesian coordinate system to help memorize routes.
The paper was recently published in current Biology.
Be compatible with different aspects of memory.
Thanks to the latest developments in microscopy and genetics, scientists have been able to make different kinds of brain cells glow in different colors.
This gives researchers the ability to distinguish individual neurons and solve the question of how they connect to each other in the nervous system that makes up the brain.
This technique has been used to observe how an insect's brain tracks its direction of action and to identify brain cells that encode its speed as it moves.
With this information, insects can constantly add the current speed to their memory during the journey to calculate and track how far they have gone.
In fact, this is a rather puzzling puzzle.
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Fast-moving insects need to constantly update their memories of direction and distance while flying, while at the same time preserving those memories for several days.
These two aspects of memory, rapid renewal and long-term persistence, are often considered incompatible, but insects seem to be able to combine them.
To solve this problem, in the new study, scientists believe that freezing insects is the best way to find out.
Of course it sounds strange at first, but it has its own reasons.
Anesthesiologists all know that when a person is anesthetized, they forget something that happened before the anesthesia, but remember other things, depending on how these memories are stored.
For insects, the closest thing to anesthesia is to freeze them temporarily.
When their temperature drops to the melting temperature (0 °C), the electrical activity in the brain stops and the insect falls into a coma.
If their direction and distance memories are maintained in the form of short-term electrical activity, these memories will be erased when they are frozen.
But if they are stored in synapses between neurons as part of long-term memory, they can still be retained.
So the scientists caught ants and beetles as they left the nest, cooled them to 0 °C for half an hour, and then put the little ones back at ambient temperature.
Once ants or beetles wake up, they are placed in a strange place to see what they can do.
Photo source: Pisokas, I. et al.
Usually, when these insects are released to a strange place in their living environment, they run straight to their nests as if they had not been moved.
In other words, they move parallel to the usual path, and once they reach the expected distance, they begin to look for the entrance to the nest.
But scientists have noticed that frozen insects move in the desired direction, but do not remember the distance they should travel.
In other words, they start looking for the entrance to the nest prematurely.
A possible explanation.
At first, this conclusion is very confusing because the memory of their distance is degraded, but the memory of direction is retained.
This result did not lead to a clear distinction between short-term (forgetting) and long-term (retention) memories that the team expected.
But the scientists later suggested that the best explanation for this phenomenon is not as two separate memories, but as a common memory that combines direction and distance to code, and after freezing, the memory partially fades.
Think of it this way. Instead of remembering a distance plus a direction (angle), the ant remembers its position in xmury coordinates, the so-called Cartesian coordinate system.
Insects may have used Cartesian coordinates to remember their positions.
| Picture Design: Mandy; reference Source: Pisokas, I. et al.
If it loses part of its memory, both x and y values will be reduced, and assuming it loses a similar proportion of memory on both axes, the final distance will be shortened, but the direction (angle) will remain the same.
Perhaps insects were using Cartesian coordinates to find their way home long before Descartes formally proposed the concept.