Models of heterogeneous dopamine signaling in an insect learning and memory center
Fig 1
Diagram of the mushroom body model.
(A) Kenyon cells (KCs) respond to stimuli and project to mushroom body output neurons (MBONs) via weights WKC→MBON. These connections are dynamic variables that are modified according to a synaptic plasticity rule gated by dopamine neurons (DANs). Output neurons and dopamine neurons are organized into compartments (dotted rectangles). External signals convey, e.g., reward, punishment, or context to the mushroom body output circuitry according to weights Wext. A linear readout with weights Wreadout determines the behavioral output of the system. Connections among output neurons, dopamine neurons, and feedback neurons (gray) are determined by weights Wrecur. Inset: expanded diagram of connections in a single compartment. (B) The form of the dopamine neuron-gated synaptic plasticity rule operative at KC-to-MBON synapses. ΔT is the time difference between Kenyon cell activation and dopamine neuron activation. (C) Illustration of the change in KC-to-MBON synaptic weight ΔW following forward and backward pairings of Kenyon cell and dopamine neuron activity.