Linear and nonlinear measures predict swimming in the leech
Stimulation of a trigger interneuron of an isolated nerve cord preparation of the medicinal leech, Hirudo medicinalis, sometimes leads to swimming; sometimes it does not. We investigate signals transmitted in the ventral cord of the leech after stimulation and seek quantitative measures that would make it possible to distinguish signals that predict swimming from those that do not. We find that a number of linear as well as nonlinear measures provide statistically significant distinctions between the two kinds of signals. The linear measures are the time dependence of (i) the standard deviation and (ii) the autocorrelation function at a small time delay. The nonlinear measures are (i) a measure of nonlinear predictability and (ii) the time dependence of a measure of the size of the embedded signal trajectory. Calculations using surrogate data suggest that the differences between the two classes of signals are dynamical as well as statistical.
Cellucci
CJ
Department of Physics, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010 and Department of Physics, Ursinus College, Collegeville, Pennsylvania 19426The Arthur P. Noyes Clinical Research Center, Norristown, Pennsylvania 19401, USA.
Brodfuehrer
PD
Acera-Pozzi
R
Dobrovolny
H
Engler
E
Los
J
Thompson
R
Albano
AM