title: A Class of Visual Neurons with Wide-Field Properties Is Required for Local Motion Detection.
abstract: Visual motion cues are used by many animals to guide navigation across a wide range of environments. Long-standing theoretical models have made predictions about the computations that compare light signals across space and time to detect motion. Using connectomic and physiological approaches, candidate circuits that can implement various algorithmic steps have been proposed in the Drosophila visual system. These pathways connect photoreceptors, via interneurons in the lamina and the medulla, to direction-selective cells in the lobula and lobula plate. However, the functional architecture of these circuits remains incompletely understood. Here, we use a forward genetic approach to identify the medulla neuron Tm9 as critical for motion-evoked behavioral responses. Using in vivo calcium imaging combined with genetic silencing, we place Tm9 within motion-detecting circuitry. Tm9 receives functional inputs from the lamina neurons L3 and, unexpectedly, L1 and passes information onto the direction-selective T5 neuron. Whereas the morphology of Tm9 suggested that this cell would inform circuits about local points in space, we found that the Tm9 spatial receptive field is large. Thus, this circuit informs elementary motion detectors about a wide region of the visual scene. In addition, Tm9 exhibits sustained responses that provide a tonic signal about incoming light patterns. Silencing Tm9 dramatically reduces the response amplitude of T5 neurons under a broad range of different motion conditions. Thus, our data demonstrate that sustained and wide-field signals are essential for elementary motion processing.
authors.affiliation: Department of Neurobiology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Yvette E
authors.initials: YE
authors.lastname: Fisher
authors.affiliation: Department of Neurobiology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Jonathan C S
authors.initials: JC
authors.lastname: Leong
authors.affiliation: European Neuroscience Institute, Grisebachstrasse 5, 37077 Göttingen, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Sporar
authors.affiliation: European Neuroscience Institute, Grisebachstrasse 5, 37077 Göttingen, Germany.
authors.forename: Madhura D
authors.initials: MD
authors.lastname: Ketkar
authors.affiliation: Department of Neurobiology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Daryl M
authors.initials: DM
authors.lastname: Gohl
authors.affiliation: Department of Neurobiology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Clandinin
authors.affiliation: European Neuroscience Institute, Grisebachstrasse 5, 37077 Göttingen, Germany. Electronic address: m.silies@eni-g.de.
authors.forename: Marion
authors.initials: M
authors.lastname: Silies
mesh_terms: D000818:Animals; D004330:Drosophila; D005260:Female; D007395:Interneurons / Q000502:physiology*; D009039:Motion Perception / Q000502:physiology*