Figure 4.

Summary Diagram of the Neuronal Mechanisms of Tinbergen-Type Decision Making in Lymnaea

Strong touch stimulation to the lips induces a burst of firing in PeD12, which in turn excites PlB via a monosynaptic excitatory connection. PlB inhibits the feeding network at multiple levels and stops ongoing feeding. However, PlB does not play a role in triggering withdrawal in response to touch. Thus, there is a clear asymmetry in the function of these two cells, with PeD12 coordinating activation of withdrawal with inhibition of feeding, whereas PlB is only involved in the inhibition of ongoing feeding in response to aversive touch. Bars indicate excitatory synaptic connection, and dots indicate inhibitory synaptic connections. Resistor symbols indicate electrotonic coupling between withdrawal-response motoneurons.