Proceedings Article | 30 April 2003
Proc. SPIE. 5110, Fluctuations and Noise in Biological, Biophysical, and Biomedical Systems
KEYWORDS: Safety, Phase modulation, Nerve, Computer simulations, Neural networks, Nervous system, In vivo imaging, Systems modeling, Neurons, Axons
The mechanisms involved in respiratory rhythm and in its persistence along lifetime have not been completely elucidated yet. The debate if they rely on pacemaker units or on the emerging properties of neural networks is still on. We propose a simple model taking advantage of the synaptic noise and allowing to bridge network and pacemaker theories. The pBC (reticular preBotzinger Complex) and PC (pneumotaxic center) are two randomly and sparsely connected excitatory networks. pBC excites PC that in turn, strongly inhibits pBC. As a part of the reticular formation, the pBC, receives many uncorrelated inputs (noise). The model reproduces most of the experimental observations. Once started, the pBC, whose activity is started by synaptic noise, increase of activity is an emerging property of the excitatory network. This activates the PC that in turn inhibits the pBC and starts the expiration. If, for any reason, noise becomes too low, the network becomes silent, and pacemakers become the only active units able to restart a new inspiration. Safety measures of this kind are very much expected in the operation of a system as vital as respiration. Simulations using an enhanced biologically plausible model of neurons fully support the proposed model.
