Pause for Thought
Photo: The acoustic CR neuromodulation method disturbs the synchronous firing of the neurons by using electrical stimulation. Recent research work has now shown that this can be improved by incorporating sufficiently long pauses.
People with tinnitus constantly hear annoying sounds, which can detract from their quality of life. This noise is triggered by malfunctions in the brain due to neuron clusters firing excessively and synchronously. The acoustic CR neuromodulation method developed by JARA-BRAIN scientist Prof. Peter Tass is a promising treatment. This method disturbs the synchronous firing of the neurons by using electrical stimulation. Recent research work has now shown that this therapeutic approach can be improved by incorporating sufficiently long pauses between the stimulation of the neurons even if very weak stimulations are used.
Scientists at Jülich's Institute of Neuroscience and Medicine generated a cluster of 256 neurons on a computer in order to test the modified stimulation patterns. The cluster was simulated in such a way that the neurons were
hypersynchronously active and sent their signals simultaneously. "The reasons for such pathological synchronous hyperactivity are malfunctions in the brain. In healthy individuals, neurons do not all fire at once or as hypersynchronously, but rather in a selectively networked and coordinated manner in functionally relevant groups," explains Prof. Peter Tass, head of Neuromodulation (INM-7).
The researchers stimulated the simulated neuron cluster with short electric signals according to a pattern precisely determined in space and time on the principle of Coordinated Reset (CR) stimulation. In this method developed by Tass, different parts of an affected neuron cluster are selectively disturbed by a specially designed sequence of mild stimuli. Over a period of time, the entire neuron cluster no longer fires synchronously and thus "unlearns" its undesirable synchronous hyperactivity.
To date, researchers had assumed that such stimulation was necessary over a considerable period for several hours each day. "In the course of our research, it occurred to us that we should investigate whether pauses in treatment affected the success of the stimulation," says the Jülich scientist looking back. Using the simulated neuron cluster, the researchers varied the duration of the stimulation as well as the pauses and made an astonishing discovery. With certain combinations, the long-term desynchronizing effect was maintained even if the stimuli were actually too weak. "From previous research, we know that with long-term CR stimulations an effect on the neuron clusters can only be achieved if the intensity of the stimulus has a certain minimum strength. However, the computer simulations showed that with the correct breaks a significantly lower intensity was sufficient, which would otherwise not be effective," says Tass.