Reiser Lab
Virtual-reality flight arena
We study the spectacular behavioral repertoire and the molecular genetic toolkit of the fly to uncover the functional organization of neural circuits that orchestrate our favorite behaviors. All projects in the lab combine multiple approaches; we explore the rich behaviors of walking and flying flies supported by extensive instrument development efforts, along with electrophysiology, calcium imaging, and computational methods.
We work closely with several groups within Janelia, especially the labs of Vivek Jayaraman, Gerry Rubin and the Fly Olympiad Project Team.
Our interests in fly vision and thermosensing have lead us to studying an elaborate learned behavior—visual place memory (or how a fly knows where it is). Our approach towards behavioral neurogenetics, makes use of precise measurements of specific behavior in combination with small scale screens of anatomically preselected driver lines (graciously supplied by the Rubin lab) for inactivating small subsets of neurons. The other major effort in the lab works towards establishing and using physiological measurements to understand the roles of identified neurons in specific features of well-defined behaviors.
While we are broadly interested in most aspects of fly behavior, the primary projects in the lab are:
- The sensory basis of gravity sensing (Nikolai Kladt)
- The functional organization of the early visual system—the lamina and medulla (behavioral genetics: John Tuthill in collaboration with Aljoscha Nern and Gerry Rubin; electrophysiology: John Tuthill; imaging: James Strother in collaboration with Vivek Jayaraman)
- Visual place memory (Tyler Ofstad and Laura Henderson as collaboration with Charles Zuker; recent effort into the role of the central complex as a collaboration with Arnim Jenett and Gerry Rubin).
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Michael Reiser Lab Head
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Eyal Gruntman Postdoctoral Associate
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Stephen Holtz Research Staff
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Mai Morimoto
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Edward Rogers Research Staff
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James Strother Postdoctoral Associate
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Shiuan-Tze Wu Research Staff
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Emily Willis
Janelia Publications
When the contrast of an image flickers as it moves, humans perceive an illusory reversal in the direction of motion. This classic illusion, called reverse-phi motion, has been well-characterized using psychophysics, and several models have been proposed to account for its effects. Here, we show that Drosophila melanogaster also respond behaviorally to the reverse-phi illusion and that the illusion is present in dendritic calcium signals of motion-sensitive neurons in the fly lobula plate. These results closely match the predictions of the predominant model of fly motion detection. However, high flicker rates cause an inversion of the reverse-phi behavioral response that is also present in calcium signals of lobula plate tangential cell dendrites but not predicted by the model. The fly's behavioral and neural responses to the reverse-phi illusion reveal unexpected interactions between motion and flicker signals in the fly visual system and suggest that a similar correlation-based mechanism underlies visual motion detection across the animal kingdom.
The ability of insects to learn and navigate to specific locations in the environment has fascinated naturalists for decades. The impressive navigational abilities of ants, bees, wasps and other insects demonstrate that insects are capable of visual place learning, but little is known about the underlying neural circuits that mediate these behaviours. Drosophila melanogaster (common fruit fly) is a powerful model organism for dissecting the neural circuitry underlying complex behaviours, from sensory perception to learning and memory. Drosophila can identify and remember visual features such as size, colour and contour orientation. However, the extent to which they use vision to recall specific locations remains unclear. Here we describe a visual place learning platform and demonstrate that Drosophila are capable of forming and retaining visual place memories to guide selective navigation. By targeted genetic silencing of small subsets of cells in the Drosophila brain, we show that neurons in the ellipsoid body, but not in the mushroom bodies, are necessary for visual place learning. Together, these studies reveal distinct neuroanatomical substrates for spatial versus non-spatial learning, and establish Drosophila as a powerful model for the study of spatial memories.
Drosophila melanogaster is a model organism rich in genetic tools to manipulate and identify neural circuits involved in specific behaviors. Here we present a technique for two-photon calcium imaging in the central brain of head-fixed Drosophila walking on an air-supported ball. The ball's motion is tracked at high resolution and can be treated as a proxy for the fly's own movements. We used the genetically encoded calcium sensor, GCaMP3.0, to record from important elements of the motion-processing pathway, the horizontal-system lobula plate tangential cells (LPTCs) in the fly optic lobe. We presented motion stimuli to the tethered fly and found that calcium transients in horizontal-system neurons correlated with robust optomotor behavior during walking. Our technique allows both behavior and physiology in identified neurons to be monitored in a genetic model organism with an extensive repertoire of walking behaviors.
Changes in behavioral state modify neural activity in many systems. In some vertebrates such modulation has been observed and interpreted in the context of attention and sensorimotor coordinate transformations. Here we report state-dependent activity modulations during walking in a visual-motor pathway of Drosophila. We used two-photon imaging to monitor intracellular calcium activity in motion-sensitive lobula plate tangential cells (LPTCs) in head-fixed Drosophila walking on an air-supported ball. Cells of the horizontal system (HS)--a subgroup of LPTCs--showed stronger calcium transients in response to visual motion when flies were walking rather than resting. The amplified responses were also correlated with walking speed. Moreover, HS neurons showed a relatively higher gain in response strength at higher temporal frequencies, and their optimum temporal frequency was shifted toward higher motion speeds. Walking-dependent modulation of HS neurons in the Drosophila visual system may constitute a mechanism to facilitate processing of higher image speeds in behavioral contexts where these speeds of visual motion are relevant for course stabilization.