Memory 'may be built with Lego-like building blocks of knowledge'

How does our brain create memories and store information?

While many neuroscientists consider the human brain as being totally malleable, a Swiss scientist has suggested that its neurons may be acting like Lego bricks — the basic building blocks of knowledge.

Lego bricks are used to build all kinds of structures, but you cannot change the bricks themselves.

According to Henry Markram at the Swiss Federal Institute of Technology in Lausanne, our brains create new memories by rearranging discrete and fundamental building blocks of knowledge.

"We have repeatedly observed how synapses change in response to stimulation and experience, but the question we were trying to answer was whether this is happening on top of a clean slate or on top of some kind of prearranged organisation," New Scientist quoted him, as saying.

In order to answer this question, Markham and his colleagues figured out how to listen to the electrical activity in individual brain cells using needles threaded with wire.

They performed more than 200 experiments on a pair of two-week-old rats using the technique.

They listened to the noise made by groups of 12 neurons, exciting one cell at a time and noting the response from the others in order to determine the shared connections between neurons.

If the brain can be flexibly moulded by experience, then the probability of one neuron being linked to another would be equal.

Instead, Markram and his team found the neurons behaved according to something he calls the 'common-neighbour rule', more likely to be linked based on shared neighbouring neurons.

The researchers then constructed a computer simulation of 2000 neurons and applied the rule to determine how the virtual brain cells would link together.

When the tests were replicated on rat brains, the results were almost the same.

They also found that the 'common neighbour rule' created groups of 40 to 50 linked neurons', which Markram thinks are the 'Lego blocks' of memory.

"These are the smallest units of the brain that can hold knowledge. What we need to know now is what kind of knowledge they contain," he said.

Markram said this was the first experimental evidence that the basic building blocks of knowledge are built into the brain.

He suggested that these building blocks could act as placeholders, waiting to be filled as we acquire new experience.

The study is published in the Proceedings of the National Academy of Sciences.