Día y hora: Viernes 15 de Marzo, 12:00 horas. 

Titulo: Noise-induced activity suppression in nature: experiments and theory

Ponente: Prof. Joaquín J. Torres. Universidad de Granada. 

Abstract: The inverse stochastic resonance (ISR) phenomenon consists in an unexpected suppression in the activity of a natural system under the influence of noise. First evidence such noise induced activity supression has been observed in the pacemaker activity of the squid giant axon in the presence of moderate values of noise. A possible requirement for this phenomenon is the existence of a bistable regime in the behavior of the system. The first experimental demonstration of ISR has been recently reported in an in vitro preparation of a cerebral purkinje cells. Also in a recent work, we have demonstrated that ISR not only emerges in a single neuron but also it can appear in neuronal populations and in the presence of short-term synaptic plasticity. In this last case, synaptic noise can induce double ISR behaviour. On the other hand, the recent report of ISR behaviour in other systems such as in nematic liquid cristals and ecological systems indicate that ISR is a very general emerging phenomenon in nature. Then, in this talk, I report a general theoretical framework we recently developed to explain the possible emergence of ISR in a general bistable system, and conclude on conditions the potential function which drives the dynamics must accomplish. We show that such an intriguing, and apparently widely observed, phenomenon ensues in the case of an asymmetric potential function when the high activity minimum state of the system is metastable with the largest basin of attraction and the low activity state is the global minimum with a smaller basin of attraction. We  will discuss on the relevance of such a picture to understand the ISR features and to predict its general appearance in other natural systems that share the requirements described here. Finally, I report another intriguing non-standard stochastic resonance in our system, which occurs in the absence of any weak signal input into the system and whose emergence can be explained, with the ISR, within our theoretical framework in terms of the shape of the potential function.




Un saludo. 



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Daniel Manzano
Electromagnetism and Condensed Matter Department
University of Granada
Facultad de Ciencias, Av. Fuentenueva s/n
Granada 18071, Spain
Phone: +34 958241000  Ext: 20569
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Daniel Manzano
Electromagnetism and Condensed Matter Department
University of Granada
Facultad de Ciencias, Av. Fuentenueva s/n
Granada 18071, Spain
Phone: +34 958241000  Ext: 20569