Distinct sensory representations of wind and near-field sound in the Drosophila brain

Behavioural responses to wind are thought to have a critical role in controlling the dispersal and population genetics of wild Drosophila species^(1, 2), as well as their navigation in flight^3, but their underlying neurobiological basis is unknown. We show that Drosophila melanogaster, like wild-caught Drosophila strains^4, exhibits robust wind-induced suppression of locomotion in response to air currents delivered at speeds normally encountered in nature^(1, 2). Here we identify wind-sensitive neurons in Johnston's organ, an antennal mechanosensory structure previously implicated in near-field sound detection (reviewed in refs 5 and 6). Using enhancer trap lines targeted to different subsets of Johnston's organ neurons^7, and a genetically encoded calcium indicator^8, we show that wind and near-field sound (courtship song) activate distinct populations of Johnston's organ neurons, which project to different regions of the antennal and mechanosensory motor centre in the central brain. Selective genetic ablation of wind-sensitive Johnston's organ neurons in the antenna abolishes wind-induced suppression of locomotion behaviour, without impairing hearing. Moreover, different neuronal subsets within the wind-sensitive population respond to different directions of arista deflection caused by air flow and project to different regions of the antennal and mechanosensory motor centre, providing a rudimentary map of wind direction in the brain. Importantly, sound- and wind-sensitive Johnston's organ neurons exhibit different intrinsic response properties: the former are phasically activated by small, bi-directional, displacements of the aristae, whereas the latter are tonically activated by unidirectional, static deflections of larger magnitude. These different intrinsic properties are well suited to the detection of oscillatory pulses of near-field sound and laminar air flow, respectively. These data identify wind-sensitive neurons in Johnston's organ, a structure that has been primarily associated with hearing, and reveal how the brain can distinguish different types of air particle movements using a common sensory organ

Distinct Sensory Representations of Wind and Near-Field Sound in the Drosophila Brain

Behavioral responses to wind are thought to play a critical role in controlling the dispersal and population genetics of wild Drosophila species, as well as their navigation in flight, but their underlying neurobiological basis is unknown. I show that Drosophila melanogaster, like wild-caught Drosophila strains, exhibits robust wind-induced suppression of locomotion (WISL), in response to air currents delivered at speeds normally encountered in nature. Furthermore, I identify wind-sensitive neurons in the Johnston’s organ (JO), an antennal mechanosensory structure previously implicated in near-field sound detection. Using Gal4 lines targeted to different subsets of JO neurons, and a genetically encoded calcium indicator, I show that wind and near-field sound (courtship song) activate distinct JO populations, which project to different regions of the antennal and mechanosensory motor center (AMMC) in the central brain. Selective genetic ablation of wind-sensitive JO neurons in the antenna abolishes WISL behavior, without impairing hearing. Different neuronal sub-populations within the wind-sensitive population, moreover, respond to different directions of arista deflection caused by airflow and project to different regions of the AMMC, providing a rudimentary map of wind direction in the brain. Importantly, sound- and wind-sensitive JO neurons exhibit different intrinsic response properties: the former are phasically activated by small, bidirectional displacements of the aristae, while the latter are tonically activated by unidirectional, static deflections of larger magnitude. These different intrinsic properties are well suited to the detection of oscillatory pulses of near-field sound and laminar airflow, respectively. These data identify wind-sensitive neurons in JO, a structure that has been primarily associated with hearing, and reveal how the brain can distinguish different types of air particle movements, using a common sensory organ

A Circuit Mechanism for Differentiating Positive and Negative Associations

The ability to differentiate stimuli predicting positive or negative outcomes is critical for survival, and perturbations of emotional processing underlie many psychiatric disease states. Synaptic plasticity in the basolateral amygdala complex (BLA) mediates the acquisition of associative memories, both positive1,2 and negative3–7. Different populations of BLA neurons may encode fearful or rewarding associations8–10, but the identifying features of these populations and the synaptic mechanisms of differentiating positive and negative emotional valence have remained an enigma. Here, we show that BLA neurons projecting to the nucleus accumbens (NAc projectors) or the centromedial amygdala (CeM projectors) underwent opposing synaptic changes following fear or reward conditioning. We found that photostimulation of NAc projectors supports positive reinforcement while photostimulation of CeM projectors mediates negative reinforcement. Photoinhibition of CeM projectors impaired fear conditioning and enhanced reward conditioning. We then characterized these functionally-distinct neuronal populations by comparing their electrophysiological, morphological and genetic features. We provide a mechanistic explanation for the representation of positive and negative associations within the amygdala