HOW DO THE MUSHROOM BODIES REGULATE HABIT FORMATION IN <EM>DROSOPHILA?</EM>

Classical learning forms an association between a neutral external stimulus and a consequence of innate value. Conversely, operant learning associates the animal’s own behavior with such consequences; eventually, habits form which ensure fast and efficient behaviors. These types of learning can reciprocally interact with each other, with classical learning prioritized. For instance, in Drosophila, exposed to the two types of learning simultaneously, the classical stimulus is dominant. Doubling the training period shifts learning to the operant component, enabling habit formation in flies. Genetically silencing the Mushroom Bodies (MBs) in the fly brain, abolishes the need for extended training and premature habits form. In a genetic screen of MB output neurons (MBONs), MBON-02 was found to mediate the regulation of habit formation originating in the MBs. We use trans-tango and retro-tango to complete the circuit between MBON-02 and known operant learning centers in the ventral nerve cord: b1 and b3 motor neurons and validate it with connectomic data. Through behavioral testing, we also narrow down which types of MB cells (Kenyon cells; KCs) are necessary for the dominance of classical stimuli, as well as what sensory information they process in the context of habit formation.