Voltage-dependent switching of sensorimotor integration by a lobster central pattern generator.

Behavioral adaptations and the underlying neural plasticity may not simply result from peripheral information conveyed by sensory inputs. Central neuronal networks often spontaneously generate neuronal activity patterns that may also contribute to sensorimotor integration and behavioral adaptations. The present study explored a novel form of sensory-induced plasticity by which the resulting changes in motor output depend essentially on the preexisting functional state of an identified neuron of an endogenously active central network. In the isolated lobster stomatogastric nervous system, electrical stimulation of a mechanosensory nerve transiently inactivated rhythmic spike bursting in the lateral pyloric (LP) neuron of the pyloric motor pattern-generating network. Repeated sensory nerve stimulation gradually and long-lastingly strengthened the bursting of the LP neuron to the detriment of sensory-elicited inactivation. This strengthening of pyloric-timed rhythmic activity was enhanced by experimental depolarization of the neuron. Conversely, when the LP neuron was hyperpolarized, the same sensory stimulation paradigm now gradually increased the susceptibility of the pyloric-timed bursting of the network neuron to sensory-elicited inactivation. Modulation of depolarization-activated and hyperpolarization-activated ionic conductances that underlie the intrinsic bursting properties of the LP neuron may contribute via differential voltage-dependent recruitment and effects to the respective adaptive processes. These data therefore suggest a novel state-dependent mechanism by which an endogenously active central network can decrease or increase its responsiveness to the same sensory input.