| Alterations of the temporal pattern of individual neurons impulse discharges, especially the transition from single spike activity (tonic firing) to grouped discharges (bursts), play an important role for neuronal information processing and synchronization in many physiological processes (sensory encoding, information binding, hormone release, sleep-wake cycles) as well as in disease (Parkinson, epilepsy). To examine the impact of the neuronal dynamics on the neuronal synchronization we have used Hodgkin-Huxley-type model neurons with subthreshold oscillations which can be tuned from pacemaker-like tonic firing to bursting with a broad range of chaotic dynamics in between. Synchronization studies with gap-junction coupled neurons revealed mutual interdependencies between the alterations of the neurons' coupling strength and neurons' activity patterns. The neurons synchronize easiest when they are operating in the periodic bursting regime. Stronger coupling strengths are needed when the neurons exhibit chaotic discharges. Surprisingly, the highest coupling strengths are required in the periodic tonic firing regime. This seemingly simple, periodic pattern is obviously governed by more complex dynamics than expected from a conventional pacemaker neuron. The elucidation of some obviously hidden dynamics may help to explain the experimentally and clinically well documented phenomena that tonic-to-bursting transitions are closely associated with neuronal synchronization. Supported by the EU Network of Excellence BioSim, Contract No. LSHB-CT-2004-005137 |
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