EN
Nonlinear oscillatory processes are discussed under the influence of external signals to improve the understanding of signal interaction with and within biological systems. The biological endogeneous rhythms are modelled by self-sustained oscillations (limit cycles). Main emphasis is on the combined influence of very slow and very fast stimuli compared to the relevant internal frequencies and on additional effects caused by external and internal noise sources. The models represent arrays of coupled passive and active nonlinear oscillators, an external harmonic signal stimulates the input oscillator (initial stage of signal chain). Signal transfer through the pathway is studied under the influence of noise. Different noise contributions are considered, including spatially-coherent and spatially-incoherent sources. Results reveal a stochastic resonance kind of behaviour at different stages of the signal transfer, the harmonic signal is transduced through the whole system of coupled oscillators. The combined action of different noise exhibits constructive as well as destructive influences on signal amplification. In addition, the influence of noise on the synchronous behaviour of coupled active systems is investigated. Noise-induced synchronization as well as desynchronization of the output signal to the external drive result. Besides signal amplification the systems exhibit the property to decode the frequency encoded information.