A neuronal circuit approach to habituation and dishabituation mechanisms in Drosophila melanogaster

Neuronal circuits universally recognize novel stimuli, but unpredicted features in a stimulus amplify its importance, shaping attentive reactions. Habituation, the gradual reduction of responses to repetitive stimuli, and its counterpart, dishabituation, the reversal of habituated responses upon exposure to novel stimuli, are fundamental processes that organisms employ to navigate their environment efficiently. Although mechanisms driving Habituation/Dishabituation remain partly understood, the communication within neuronal circuits, which ostensibly underlies these choices, is an emerging field. It is understood that when the nature of the habituator is different from the dishabituator, the two stimuli engage distinct, but likely converging circuitry and dishabituation is efficient. In contrast, when the habituator and the dishabituator are of the same nature (i.e. two odors), it is unclear whether this homo-sensory habituation/dishabituation engages distinct neuronal circuits, different than the ones driving hetero-sensory dishabituation. In this work we show that dopaminergic reinforcement in the Mushroom Body (MB) neurons is essential to encode the identity of the dishabituator stimulus (yeast odor & electric shock). GABAergic neurotransmission from APL neurons to the MB is also required for homo-sensory dishabituation with yeast odor. The MB appears to act as the Executive Control Unit using the information to promote habituation through the α΄/β΄ lobe and dishabituation through the α/β & γ lobes. We propose a multifaceted approach to investigate the neural circuits and mechanisms driving these phenomena, contributing to our understanding of basic behavioral plasticity.