The Journal of Neurophysiology Vol. 82 No. 6 December 1999, pp. 3378-3391
Copyright ©1999 by the American Physiological Society
Pattern Generation in the Buccal System of Freely Behaving
Lymnaea stagnalis
Rene F.
Jansen,
Anton W.
Pieneman, and
Andries ter
Maat
Faculty of Biology, Vrije Universiteit, 1081 HV Amsterdam, The
Netherlands
Jansen, Rene F.,
Anton W. Pieneman, and
Andries ter Maat.
Pattern Generation in the Buccal System of Freely Behaving
Lymnaea stagnalis. J. Neurophysiol. 82: 3378-3391, 1999. Central pattern generators (CPGs) are neuronal circuits that
drive active repeated movements such as walking or swimming. Although
CPGs are, by definition, active in isolated central nervous systems,
sensory input is thought play an important role in adjusting the output
of the CPGs to meet specific behavioral requirements of intact animals.
We investigated, in freely behaving snails (Lymnaea
stagnalis), how the buccal CPG is used during two different behaviors, feeding and egg laying. Analysis of the relationship between
unit activity recorded from buccal nerves and the movements of the
buccal mass showed that electrical activity in
laterobuccal/ventrobuccal (LB/VB) nerves was as predicted from
in vitro data, but electrical activity in the posterior jugalis nerve
was not. Autodensity and interval histograms showed that during feeding
the CPG produces a much stronger rhythm than during egg laying. The
phase relationship between electrical activity and buccal movement
changed little between the two behaviors. Fitting the spike trains
recorded during the two behaviors with a simple model revealed
differences in the patterns of electrical activity produced by the
buccal system during the two behaviors investigated. During egg laying
the bursts contained less spikes, and the number of spikes per burst
was significantly more variable than during feeding. The time between two bursts of in a spike train was longer during egg laying than during
feeding. The data show what the qualitative and quantitative differences are between two motor patterns produced by the buccal system of freely behaving Lymnaea stagnalis.
