NEURONS—commonly known as nerve cells—communicate using electrical signals. However, sometimes communication is drowned out by more intense electrical signals, caused when each neuron continually excites and influences its neighbours.
This collective activity, known as bursting, has been recognised by neuroscientists for more than a decade. Sometimes it is beneficial—for example to help the correct neural connections to form in young brains. Sometimes, though, it is less benign. Epileptic fits appear to be neural bursts that have run out of control. Such fits can currently be controlled only by drugs. However, an attempt to link nerve cells directly to computers may be about to change that, by allowing the bursts associated with epileptic fits to be controlled directly.
Daniel Wagenaar of Caltech, in Pasadena, and Steven Potter of Georgia Tech, in Atlanta, have been growing rat and mouse neurons on arrays of electrodes connected to a computer. The first idea was to use the neurons to control the computer. The researchers' hope was that the neurons would add an ability to learn to a computer program.
However,the experiment failed, largely because of bursting. So Mr Wagenaar, Dr Potter and another researcher at Georgia Tech, Radhika Madhavan, set out to defeat bursting. Their results, published recently in the Journal of Neuroscience, show that this is possible using electrical stimulation alone. After a series of experiments involving various numbers of electrodes and various frequencies of stimulation, they have found that using an array of 25 electrodes and a stimulation rate of 50 pulses a second produces the desired suppression, but only if the electrodes themselves are out of synch with each other. The best results of all are obtained when the response to one burst of stimuli is used to regulate the rate and voltage of the next. And, once bursting is suppressed this way, the neurons revert rapidly to normal behaviour.
To exploit the potential of this work, the researchers have just formed a collaboration with Robert Gross of the Emory School of Medicine, also in Atlanta. Dr Gross, a surgeon, is already skilled at implanting stimulating electrodes into human brains. The group hopes to implant electrodes that can detect electrical activity as well as stimulate it. That way, stimulation can be given when needed—when a fit is actually beginning—rather than all the time. If that works, it could transform the lives of epileptics who now have to live with debilitating doses of drugs.