Phase-dependent coordination of two motor programs in the buccal ganglion of a pteropod mollusk.

Rhythmic activity in two independent structures of the digestive apparatus of Clione limacina--the radula and the hooks--is coordinated by neural networks in the buccal ganglion during feeding behavior. Optical recording of neuron activity in the buccal ganglion, which allows simultaneous recording of large numbers of neurons, showed that the activity of all neurons producing volley discharges can be assigned to only two phases of a single rhythm. Instead of the four theoretically possible phases of rhythmic neural activity, all experiments yielded recordings of biphasic activity, even in conditions of electrical stimululation of the cerebrobuccal connectives, which triggers rhythmic movements of this apparatus in preparations. These data demonstrate the phase-dependent coordination of two independent rhythmic food-procuring movements in Clione.