UCL News


UCL in the News: Brain's memory capacity less than thought

14 September 2007

About 100 billion neurons, or brain cells, make up the average adult's brain, but the computer-based discovery shows our memory isn't based simply on neuron numbers.

Instead, the limited amount of connections a neuron can make to other neurons may cut memory capacity.

"People have suspected this for a long time, but we've shown it's possible for the first time in realistic memory networks," said study co-author Peter Latham [Gatsby Computational Neuroscience Unit at UCL]. …

Neurons produce electrical signals that travel through each cell's 10,000-or-so "cables" of nerve tissue, each connected to another neuron to form a "network" of communicating cells. Latham explained, however, that neurons often produce random, meaningless signals that create noise in neuron-to-neuron speech. …

Neuroscientists think that neurons organize themselves into distinct networks, and that the strength of each synapse, or neuron-to-neuron connection, is what helps form a memory. To realistically simulate such networks, Latham and his colleagues used advanced computer models of brain activity.

The team found that as neurons' connection strength increased, so did the strength of the noisy signals.

"You can have as many neurons as you want in a network, but as memories are added and the connections get stronger, the noise gets so amplified that a network can only store about 500 memories," he said. …

"It's certainly possible that the brain is organized into thousands, or tens of thousands, of isolated networks," he said. Such a scenario would vastly multiply our brain's memory capacity but, more likely, the networks all link up in some way to form a redundant "Internet" of memory better able to create and recall memories. …

 "We aren't even sure if memories are concentrated in one part of the brain, or spread around to all of it," he said. "Our finding is just one tiny piece of an exceedingly large puzzle I don't think will be solved until a thousand years from now."

Dave Mosher, MSNBC