Neural Trickery

Do the neurons in your brain operate like simple on-off switches or are they, in fact, much more sophisticated than that?

Actors and comedians will tell you that their work is all about timing. It's not just the words, it's the rhythm and pace that count. A similar principle applies in computer programming, where one of the big problems is trying to get the various constituents of a computer to work well together in terms of timing. Neuroscientists are now beginning to suspect the same thing about the way the brain operates and, if this theory is correct, it will imply that the brain is actually much more powerful than was previously thought.

The new theory concerning timing as all about the timing of nerve impulses. Standard thinking on the brain is that a neuron's message to its neighbour is carried by the average number of impulses sent over a set period. According to this view, a neuron operates like the overflow in a basin. The basin fills up with water, but does not overflow until a critical volume occurs. In the model of the brain, each neuron collects inputs from neighbouring cells and only passes on its message to the next cell when a threshold is reached.

However, according to new research, this 'basin' theory may be wrong and neurons may act like parts of a telegraph system that read incoming impulses, or 'spikes', as if they were dots or dashes in Morse code. Instead of waiting for a threshold to be reached, each neuron continually transmits information about its current status. In effect, it is constantly telling its neighbour how near to being full the basin is.

With such a system, each neuron has the capacity to encode up to 100 times more data per second than was previously thought. Taking this in the context of the billions of neurons in the brain, and considering that each neuron has the ability to communicate with 10,000 others, it is clear that the computational capacity of the brain soars to unimaginable heights.

This theory has actually been around for a while, but failed to gain widespread acceptance for two main reasons. Firstly, there doesn't seem to be much reason why the brain should require the immense extra computational power that this different model implies. Secondly, most experimental evidence seemed to indicate that the simpler model was correct.

However, according to some neuroscientists, this is now changing. They claim that the 'temporal coding' view of the brain is not incorrect, but that the experiments designed to test it, were flawed. In most of these experiments, neurons were given very simple stimuli, a situation most unlike what happens in the real world. Now experiments have been constructed and carried out that bear more of a resemblance to what happens in real life. From the results of these, neuroscientists have gathered fresh evidence that supports the temporal code theory.

So, if you previously thought that the brain was an unbelievably sophisticated processor of information, you may have to think again. It may turn out to be more powerful than was realised by orders of magnitude.

Issue 2: Contents | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9