Noisy precursors of bifurcations in a neurodynamical model for disease states of mood disorders

We study the effect of noise on a nonlinear neurodynamical model for diseas e states of recurrent affective disorders. Specifically, we consider how no ise affects a model state with periodic event generation close to period-do ubling bifurcations. Our simulations demonstrate noisy precursors of the bi furcations. The precursors can be seen in the return maps of the time serie s and can be quantified with a recently developed algorithm for the detecti on of unstable periodic orbits. Implications for the neurobiology and cours e of mood disorders are discussed. (C) 2000 Elsevier Science B.V. All right s reserved.