To explore how the brain learns, researchers led by Martin Tegenthoff of Ruhr University Bochum conducted a simple yet elegant experiment. They placed two needles, spaced closely apart, on the index fingertips of test subjects. The subjects perceived this as a single needle. They then stimulated a small area on the test subjects' fingertips with a vibrating membrane for three hours. The subjects were then able to distinguish between two closely spaced needles on their fingertips.

Using functional magnetic resonance imaging (fMRI) (see explanation below), the scientists were able to observe the brain during this learning process. The active area of ​​the brain that responded to fingertip stimulation had significantly increased after the three hours of learning. The simultaneous processing of the fingertip stimuli thus activated an extensive network of nerve cells.

Larger neural network - more learning success

The fMRI measurements also clearly demonstrated the extent of the individual test subjects' learning success: Those subjects whose activated brain region increased the most also had the greatest success in distinguishing between closely spaced needles. However, the changes in brain activity, like the subjects' learning success, were short-lived: After 24 hours, they had already regressed.

Learning therefore involves the formation of extensive neural networks, even if in the above case it wasn't sustained. The learning period was probably too short and wasn't repeated frequently enough. But the experiment also provides a first answer to another interesting question: Is memory space limited in the brain?

In computer technology, we're used to hard drives or memory chips with a certain number of gigabytes of storage capacity. Can a similar number be given for the brain? No, because the brain functions fundamentally differently than a computer. We have a multitude of different learning systems made up of neural networks, each of which has a potentially inexhaustible capacity. Therefore, memory shouldn't be thought of as a static hard drive, but rather as a constantly evolving network that can form almost any number of connections.

"Model calculations have shown that, theoretically, the human brain's memory would still have enough capacity even if a person were supplied with a large amount of information every day for 130 years and could also absorb this data." Our brain's memory capacity is therefore potentially unlimited, or at least we don't yet know its limits.

Explanation: functional magnetic resonance imaging (fMRI)

fMRI is a technique that can be used to visualize metabolic functions within the brain. It utilizes the different magnetic properties of oxygen-rich and deoxygenated blood to map changes in blood flow to brain areas.

Source:

Pfleger, B. et al. Functional imaging of perceptual learning in human primary and secondary somatosensory cortex. Neuron 40(3):643–53.