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When asked to explain in five words how the brain works, cognitive scientist Steven Pinker didn’t hesitate. «Brain cells follow patterns,» he replied. It’s a good effort, but it replaces one riddle with another mystery.
It has long been known that brain cells communicate by sending electrical signals to one another, and there are now many technologies to record their activity patterns: from electrodes to fMRI scanners that can detect changes in blood oxygenation .
But while this information can be collected, the meaning of these patterns remains a mystery. They seem to dance to music we can’t hear, directed by rules we don’t know.
Neurologists talk about the neural code and have made some progress in cracking it. They begin to understand some basic rules, such as when cells in specific parts of the brain are activated based on the task at hand.
Progress has been slow, but in the last decade various research teams around the world have been pursuing a much more ambitious project.
We may never be able to see the full dictionary of that code, but we can begin to glimpse the ways in which different patterns correspond to different actions.
The rat in his maze
Albert Lee and Matthew Wilson, at the Massachusetts Institute of Technology (MIT), helped establish the principles of this translation in 2002. Here’s their recipe: They first looked at the brain of a rat—one of our closest relatives in the great tree of life – while walking through a maze.
Studying the entire brain may be too ambitious, so they focused their observations on the hippocampus, an area known to be important in orientation and memory.
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More experienced London taxi drivers have larger seahorses.
If you have already heard about this part, it is possibly because of a famous study that reveals that London taxi drivers developed a larger hippocampus the more time they spent traveling the streets of the sprawling capital of the United Kingdom.
As the rat went through the maze, they recorded point by point its location on the path and simultaneously watched cells in the hippocampus light up.
Then, they pass the patterns of the cells to a mathematical algorithm that finds the pattern that best matches each part of the maze. The cells’ language is complex, but now they have the Rosetta Stone and can decode it.
They then tested the algorithm against the newly recorded patterns to see if it correctly predicted where the rat was at the time the pattern was recorded.
This doesn’t fully crack the code because we don’t know all the rules yet, and it can’t help us read patterns that don’t belong in this part of the brain or that aren’t about mazes, but it’s still a powerful tool.
speed dreams
For example, using this technique, the team could see that when the rat fell asleep after the maze, its brain repeated the specific sequence of connecting cells (which was not present in the sleep it enjoyed before running the maze).
Surprisingly, the sequence was repeated about 20 times faster during sleep. This means that the rat could walk the maze in a dream in a fraction of the time it took in real life.
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A rat can mentally replay a faster route when it is sleeping.
This could be related to the mnemonic function of the dream; repeating the memory, could have helped the rat to consolidate its learning.
And the fact that the repetition was accelerated could give us an idea of the activity behind the sudden perspective or experiences in which our life «flashes before our eyes»; when left unchecked, our thoughts can truly retrace familiar paths in»flash forward«.
More work has been done showing that these maze patterns can take us back and forth – suggesting that rats can imagine a goal, such as the end of a maze, and work their way in reverse to the point where they end. they find each other.
respond with imagination
Techniques like these, which involve highly specialized measurement systems and very complicated algorithms, can decode the brain activity of patients who are paralyzed or in a vegetative state.
These patients cannot move any of their muscles, but they may still be able to hear people talking to them in the same room. First, doctors ask patients to imagine activities that are known to activate specific regions of the brain – such as the hippocampus.
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The neurons speak to each other with electrical impulses, but it is not yet known what they say to each other.
The data is then decoded to find out which brain activity corresponds to which ideas. During future brain scans, patients can again imagine themselves playing tennis to answer yes and walking around their house to answer no – that’s the first form of communication.
There are other applications for showing the inner workings of our mind, both from theoretical science and from practical domains, such as brain-computer interfaces.
If in the future a paraplegic wants to control a mechanical arm, or even another person through a brain interface, they will rely on the same techniques to decode the information and translate it into action.
Now that the principles have been observed, the potential can be staggering.