@article {21484, title = {Higher-order neural processing tunes motion neurons to visual ecology in three species of hawkmoths}, journal = {Proceedings of the Royal Society B}, volume = {284}, year = {2017}, month = {06/2017}, pages = {20170880}, chapter = {20170880}, abstract = {

\"To sample information optimally, sensory systems must adapt to the ecological demands of each animal species. These adaptations can occur peripherally, in the anatomical structures of sensory organs and their receptors; and centrally, as higher-order neural processing in the brain. While a rich body of investigations has focused on peripheral adaptations, our understanding is sparse when it comes to central mechanisms. We quantified how peripheral adaptations in the eyes, and central adaptations in the wide-field motion vision system, set the trade-off between resolution and sensitivity in three species of hawkmoths active at very different light levels: nocturnal Deilephila elpenor, crepuscular Manduca sexta, and diurnal Macroglossum stellatarum. Using optical measurements and physiological recordings from the photoreceptors and wide-field motion neurons in the lobula complex, we demonstrate that all three species use spatial and temporal summation to improve visual performance in dim light. The diurnal Macroglossum relies least on summation, but can only see at brighter intensities. Manduca, with large sensitive eyes, relies less on neural summation than the smaller eyed Deilephila, but both species attain similar visual performance at nocturnal light levels. Our results reveal howthe visual systems of these three hawkmoth species are intimately matched to their visual ecologies.\"

}, keywords = {DEILEPHILA, ECOLOGY, MACROGLOSSUM, MANDUCA, NEURAL SUMMATION, PHYSIOLOGY, SPHINGIDAE, VISION, VISUAL PROCESSING}, url = {http://dx.doi.org/10.1098/rspb.2017.0880}, author = {St{\"o}ckl, A.L. and O{\textquoteright}Carroll, D.C. and Warrant, E.J.} } @article {21484, title = {Neural summation in the hawkmoth visual system extends the limits of vision in dim light}, journal = {Current Biology}, volume = {26}, year = {2016}, month = {03/2016}, pages = {821-826}, chapter = {821}, abstract = {

\"Most of the world\’s animals are active in dim light and depend on good vision for the tasks of daily life. Many have evolved visual adaptations that permit a performance superior to that of manmade imaging devices [1]. In insects, a major model visual system, nocturnal species show impressive visual abilities ranging from flight control [2, 3], to color discrimination [4, 5], to navigation using visual landmarks [6\–8] or dim celestial compass cues [9, 10]. In addition to optical adaptations that improve their sensitivity in dim light [11], neural summation of light in space and time\—which enhances the coarser and slower features of the scene at the expense of noisier finer and faster features\—has been suggested to improve sensitivity in theoretical [12\–14], anatomical [15\–17], and behavioral [18\–20] studies. How these summation strategies function neurally is, however, presently unknown. Here, we quantified spatial and temporal summation in the motion vision pathway of a nocturnal hawkmoth. We show that spatial and temporal summation combine supralinearly to substantially increase contrast sensitivity and visual information rate over four decades of light intensity, enabling hawkmoths to see at light levels 100 times dimmer than without summation. Our results reveal how visual motion is calculated neurally in dim light and how spatial and temporal summation improve sensitivity while simultaneously maximizing spatial and temporal resolution, thus extending models of insect motion vision derived predominantly from diurnal flies. Moreover, the summation strategies we have revealed may benefit manmade vision systems optimized for variable light levels [21].\"

}, keywords = {DEILEPHILA, NEURAL SUMMATION, PHYSIOLOGY, SPHINGIDAE, VISION, VISUAL PROCESSING}, url = {http://dx.doi.org/10.1016/j.cub.2016.01.030}, author = {St{\"o}ckl, A.L. and O{\textquoteright}Carroll, D.C. and Warrant, E.J.} } @article {21483, title = {Wide-field motion tuning in nocturnal hawkmoths}, journal = {Proceedings of the Royal Society B}, volume = {277}, year = {2010}, pages = {853-860}, chapter = {853}, abstract = {

\"Nocturnal hawkmoths are known for impressive visually guided behaviours in dim light, such as hovering while feeding from nectar-bearing flowers. This\  requires tight visual feedback to estimate and counter relative motion. Discrimination of low velocities, as required for stable hovering flight, is fundamentally limited by spatial resolution, yet in the evolution of eyes for nocturnal vision, maintenance of high spatial acuity compromises absolute sensitivity. To investigate these trade-offs, we compared responses of wide-field motion-sensitive neurons in three species of hawkmoth: Manduca sexta (a crepuscular hoverer), Deilephila elpenor (a fully nocturnal hoverer) and Acherontia atropos (a fully nocturnal hawkmoth that does not hover as it feeds uniquely from honey in bees\’\  nests). We show that despite smaller eyes, the motion pathway of D. elpenor is tuned to higher spatial frequencies and lower temporal frequencies than A. atropos, consistent with D. elpenor\’s need to detect low velocities for hovering. Acherontia atropos, however, presumably evolved low-light sensitivity without sacrificing temporal acuity. Manduca sexta, active at higher light levels, is tuned to the highest spatial frequencies of the three and temporal frequencies comparable with A. atropos. This yields similar tuning to low velocities as in D. elpenor, but with the advantage of shorter neural delays in processing motion.\"

}, keywords = {ACHERONTIA, DEILEPHILA, HOVERING, MANDUCA, NIGHT VISION, PHYSIOLOGY, SPHINGIDAE, VISION, VISUAL ACUITY, VISUAL PROCESSING}, doi = {10.1098/rspb.2009.1677}, author = {Theobald, J.C. and Warrant, E.J. and O{\textquoteright}Carroll, D.C.} }