Finding unstable periodic orbits in electroreceptors, cold receptors and hypothalamic neurons

Recently, searches for low-dimensional dynamical activity in various biolog ical preparations have become fashionable. In particular, demonstrations of the existence of unstable periodic orbits (UPOs) and bifurcations between unstable and stable states are of interest. Here, we report the detection o f UPOs in three diverse preparations: electroreceptor, cold receptor and hy pothalamic neurons. Inherent, noise mediated oscillators are common to thes e temperature sensitive neurons, and the UPOs arise in them in the absence of external periodic stimulation. The external temperature is the bifurcati on parameter. Behaviors in response to temperature transients are also show n. (C) 1999 Elsevier Science B.V. All rights reserved.