Multi-nodal regulation of olfactory dishabituation in Drosophila

Abstract

Habituation adaptively filters repeated, inconsequential sensory input, while the response to such stimuli re-emerges upon appearance of novel or salient cues (dishabituation).However, the neural circuits underlying dishabituation remain poorly defined, particularly in the central nervous system. Using Drosophila olfactory habituation to the odorant 3-octanol (OCT), we dissect the circuit basis of intramodal (odor-odor) and cross-modal (footshock-odor) dishabituation. A brief yeast odor puff dishabituates intramodally, whereas footshock cross-modally and neither operate through sensitization. Genetic silencing and optogenetics demonstrate that Mushroom Body (MBs) output drives both dishabituation forms. {beta} and {gamma} Kenyon cells (KCs) mediate dishabituation, while '{beta}' Kenyon cells mediate habituation. Dopaminergic neurons encode and PAM neurons mediating appetitive and PPL1 neurons aversive dishabituation, including that triggered by footshock and OCT itself. GABAergic APL neurons and specific MB output neurons tune the balance between habituation and dishabituation, relaying signals via MBONs to the Lateral Horn, a proposed decision node. Connectomic analysis reveals inhibitory interactions supporting this balance. Collectively, we reveal a multi-node circuit that dynamically overrides, rather than erases, habituation findings offering insight into habituation deficits in intellectual disability, autism, and schizophrenia. SIGNIFICANCE STATEMENTThis study identifies a multi-node neural circuit spanning the Mushroom Bodies, dopaminergic and GABAergic modulatory neurons and the Lateral Horn, that governs intramodal and cross-modal dishabituation in Drosophila. Showing that dishabituation dynamically overrides rather than erases habituation and that distinct dopaminergic populations encode stimulus valence to bias this switch, the work reveals a general logic for how the brain flexibly regulates sensory filtering.