  The dynamics of an initial wave packed affected by random noise is considered
in the framework of a comb model. The model is relevant to a diffusion problem
in neurons where the transport of ions can be accelerated by an external random
field due to synapse fluctuations. In the present specific case, it acts as
boundary conditions, which lead to a reaction transport equation with
multiplicative noise. The temporal behavior of the mean squared displacement is
estimated analytically, and it is shown that the spreading of the initial wave
packet corresponds to Richardson diffusion.
