title: The impact of odor-reward memory on chemotaxis in larval Drosophila.
abstract: How do animals adaptively integrate innate with learned behavioral tendencies? We tackle this question using chemotaxis as a paradigm. Chemotaxis in the Drosophila larva largely results from a sequence of runs and oriented turns. Thus, the larvae minimally need to determine (i) how fast to run, (ii) when to initiate a turn, and (iii) where to direct a turn. We first report how odor-source intensities modulate these decisions to bring about higher levels of chemotactic performance for higher odor-source intensities during innate chemotaxis. We then examine whether the same modulations are responsible for alterations of chemotactic performance by learned odor "valence" (understood throughout as level of attractiveness). We find that run speed (i) is neither modulated by the innate nor by the learned valence of an odor. Turn rate (ii), however, is modulated by both: the higher the innate or learned valence of the odor, the less often larvae turn whenever heading toward the odor source, and the more often they turn when heading away. Likewise, turning direction (iii) is modulated concordantly by innate and learned valence: turning is biased more strongly toward the odor source when either innate or learned valence is high. Using numerical simulations, we show that a modulation of both turn rate and of turning direction is sufficient to account for the empirically found differences in preference scores across experimental conditions. Our results suggest that innate and learned valence organize adaptive olfactory search behavior by their summed effects on turn rate and turning direction, but not on run speed. This work should aid studies into the neural mechanisms by which memory impacts specific aspects of behavior.
authors.affiliation: Leibniz Institute for Neurobiology (LIN), Department Genetics of Learning and Memory, 39118 Magdeburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schleyer
authors.affiliation: EMBL/CRG Systems Biology Research Unit, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain.
authors.forename: Samuel F
authors.initials: SF
authors.lastname: Reid
authors.affiliation: Leibniz Institute for Neurobiology (LIN), Department Genetics of Learning and Memory, 39118 Magdeburg, Germany.
authors.forename: Evren
authors.initials: E
authors.lastname: Pamir
authors.affiliation: Leibniz Institute for Neurobiology (LIN), Department Genetics of Learning and Memory, 39118 Magdeburg, Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Saumweber
authors.affiliation: Leibniz Institute for Neurobiology (LIN), Department Genetics of Learning and Memory, 39118 Magdeburg, Germany.
authors.forename: Emmanouil
authors.initials: E
authors.lastname: Paisios
authors.affiliation: University of Edinburgh, School of Informatics, Edinburgh EH8 9AB, United Kingdom.
authors.forename: Alexander
authors.initials: A
authors.lastname: Davies
authors.affiliation: Leibniz Institute for Neurobiology (LIN), Department Genetics of Learning and Memory, 39118 Magdeburg, Germany Otto von Guericke University Magdeburg, Institute for Biology, Behavior Genetics, 39106 Magdeburg, Germany Center of Behavioural Brain Science (CBBS), Universitätsplatz 2, 39106 Magdeburg, Germany bertram.gerber@lin-magdeburg.de matthieu.louis@crg.eu.
authors.forename: Bertram
authors.initials: B
authors.lastname: Gerber
authors.affiliation: EMBL/CRG Systems Biology Research Unit, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain bertram.gerber@lin-magdeburg.de matthieu.louis@crg.eu.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Louis
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D002633:Chemotaxis / Q000502:physiology*; D004330:Drosophila; D007814:Larva; D008568:Memory / Q000502:physiology*; D009812:Odorants; D012201:Reward; D012903:Smell / Q000502:physiology*