TOO much of a good thing can be bad for you. The synchronous firing of neurons is crucial for many ordinary brain functions, but excessive, uncontrolled synchronisation might be behind the symptoms of Parkinson鈥檚 disease. Now a computer model has backed up the idea.
Parkinson鈥檚 disease has been linked to a lack of dopamine, a chemical that, among other things, dampens the transmission of signals across nerve junctions called synapses. Measuring this effect in humans is not currently possible, so and colleagues at Indiana University-Purdue University Indianapolis turned instead to a computer model of neural networks.
As they boosted signal strength, the network became more prone to switching from non-synchronised to synchronised firing. By comparing the pattern of neural signals recorded from people with Parkinson鈥檚 against those predicted by the model, the team found that in Parkinson鈥檚, the brain readily switches between synchronised and non-synchronised behaviour even when it is relaxed. This might explain the disease鈥檚 motor symptoms.
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A healthy brain fires synchronously in a brief and controlled way to coordinate motor behaviour and perform tasks. The stronger connections in the brains of people with Parkinson鈥檚 mean that attempts to coordinate behaviour trigger sustained synchrony, which may make it difficult to end a task or begin a new one (Physical Review E, in press).
鈥淭his is a simple and elegant study,鈥� says Peter Brown of the University of Oxford. 鈥淭he model beautifully captures the dynamic behaviour of the system.鈥�
