While I’m all for public interest in science, especially neuroscience, its a pity when undecided questions are reported as solved.

The issue in question is one of the neural coding of semantic information. Jason and the New Scientist article he links to describe what is known as the Grandmother Cell theory. In short, the theory argues that most distinct semantic concepts each have their own dedicated neuron which fires when we access that concept.

The problem with this theory, despite the fact that our brains are never actually this simple, is that there simply aren’t enough neurons in the right areas to encode all the possible content we might encounter. What would happen when we run out of neurons?

An alternative to the Grandmother Cell theory is the Distributed Representation theory (also called a neural network), which argues that semantic content is encoded by the specific structure of connections between neurons. This, to me, sounds much more reasonable. Realistically though (and as seemingly suggested in the article, though they don’t outright say it) is that our brains probably work in a way that combines the two theories.