Internal Structure of the Fly Elementary Motion Detector (original) (raw)
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Functional Specialization of Parallel Motion Detection Circuits in the Fly
Journal of Neuroscience, 2013
In the fly Drosophila melanogaster, photoreceptor input to motion vision is split into two parallel pathways as represented by first-order interneurons L1 and L2 (Rister et al., 2007; Joesch et al., 2010). However, how these pathways are functionally specialized remains controversial. One study (Eichner et al., 2011) proposed that the L1-pathway evaluates only sequences of brightness increments (ON-ON), while the L2-pathway processes exclusively brightness decrements (OFF-OFF). Another study (Clark et al., 2011) proposed that each of the two pathways evaluates both ON-ON and OFF-OFF sequences.
ON and OFF pathways in Drosophila motion vision
Nature, 2010
Motion vision is a major function of all visual systems, yet the underlying neural mechanisms and circuits are still elusive. In the lamina, the first optic neuropile of Drosophila melanogaster, photoreceptor signals split into five parallel pathways, L1-L5 1 .
Motion detection in flies: Parametric control over ON-OFF pathways
Experimental Brain Research, 1984
Microscopic illumination of two neighbouring photoreceptor cells within a single ommatidium induces a strong sequence-dependent response in a directionally selective, motion-sensitive neuron. The response is characterized by a strong facilitation in the preferred direction and a weaker inhibition in the reverse direction. The data suggest that for each direction of apparent movement the signal from an ON-OFF pathway is released into the neuron via a parametric control mechanism which is activated by an adjacent channel.
Journal of the Optical Society of America A, 1989
The computations performed by individual movement detectors are analyzed by intracellularly recording from an identified direction-selective motion-sensitive interneuron in the fly's brain and by comparing these results with model predictions based on movement detectors of the correlation type. Three main conclusions were drawn with respect to the movement-detection system of the fly: (1) The essential nonlinear interaction between the two movement-detector input channels can be characterized formally by a mathematically almost perfect multiplication process. (2) Even at high contrasts no significant nonlinearities seem to distort the time course of the movement-detector input signals. (3) The movement detectors of the fly are not perfectly antisymmetrical; i.e., they respond with different time courses and amplitudes to motion in their preferred and null directions. As a consequence of this property, the motion detectors can respond to some degree to stationary patterns whose brightness is modulated in time. Moreover, the direction selectivity, i.e., the relative difference of the responses to motion in the preferred and null directions, depends on the contrast and on the spatial-frequency content of the stimulus pattern.
Peripheral Visual Circuits Functionally Segregate Motion and Phototaxis Behaviors in the Fly
Current Biology, 2009
Like the mammalian visual cortex, the fly visual system is organized into retinotopic columns . A widely accepted biophysical model for computing visual motion, the elementary motion detector proposed nearly 50 years ago [3] posits a temporal correlation of spatially separated visual inputs implemented across neighboring retinotopic visual columns. Whereas the inputs are defined , the neural substrate for motion computation remains enigmatic. Indeed, it is not known where in the visual processing hierarchy the computation occurs . Here, we combine genetic manipulations with a novel high-throughput dynamic behavioral analysis system to dissect visual circuits required for directional optomotor responses. An enhancer trap screen of synapse-inactivated neural circuits revealed one particularly striking phenotype, which is completely insensitive to motion yet displays fully intact fast phototaxis, indicating that these animals are generally capable of seeing and walking but are unable to respond to motion stimuli. The enhancer circuit is localized within the first optic relay and strongly labels the only columnar interneuron known to interact with neighboring columns both in the lamina and medulla [6], spatial synaptic interactions that correspond with the two dominant axes of elementary motion detectors on the retinal lattice .
Orientation Selectivity Sharpens Motion Detection in Drosophila
Neuron, 2015
Detecting the orientation and movement of edges in a scene is critical to visually guided behaviors of many animals. What are the circuit algorithms that allow the brain to extract such behaviorally vital visual cues? Using in vivo two-photon calcium imaging in Drosophila, we describe direction selective signals in the dendrites of T4 and T5 neurons, detectors of local motion. We demonstrate that this circuit performs selective amplification of local light inputs, an observation that constrains motion detection models and confirms a core prediction of the Hassenstein-Reichardt correlator (HRC). These neurons are also orientation selective, responding strongly to static features that are orthogonal to their preferred axis of motion, a tuning property not predicted by the HRC. This coincident extraction of orientation and direction sharpens directional tuning through surround inhibition and reveals a striking parallel between visual processing in flies and vertebrate cortex, suggestin...
Two-Dimensional Motion Perception in Flies
Neural Computation, 1993
We study two-dimensional motion perception in flies using a semicircular visual stimulus. Measurements of both the H1-neuron and the optomotor response are consistent with a simple model supposing spatial integration of the outputs of correlation-type motion detectors. In both experiment and model, there is substantial H1 and horizontal (yaw) optomotor response to purely vertical motion of the stimulus. We conclude that the fly's optomotor response to a two-dimensional pattern, depending on its structure, may deviate considerably from the direction of pattern motion.