Figure 7.

Model Illustrating the Differential Role of αβ Surface and Core Neurons in Conditioned Approach and Aversion

(A) During appetitive conditioning, rewarding dopaminergic MB-M8 neurons (green) from the PAM cluster reinforces odor-activated synapses of αβ_s (blue) and αβ_c (black) neurons in the β₁ and β₂ zones of the horizontal β lobe.

(B) During testing, appetitive memory is retrieved at least in part through MB-V3 efferent neurons (dark red) that pool inputs from across the αβ ensemble in the α₃ region of the vertical α lobe tip region and drive approach behavior through a putative premotor area. Expression of conditioned approach is additionally gated in a hunger state-dependent manner by the MB-MP1 DA neurons (orange; Krashes et al., 2009).

(C) During aversive training, MB-MP1 and MB-M3 DA neurons (green) reinforce odor-activated synapses in the αβ_s region of the peduncle and only αβ_s neurons in the β₂ region of the horizontal β lobe tip.

(D) During testing, aversive memory is retrieved at least in part through MB-V3 neurons and the MB-V2α efferent neurons (both dark red) that collect inputs from the αβ_s neurons in the tip and α₂ region of the vertical α-stalk and drive avoidance behavior through the putative premotor area.