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Higher-order motion sensitivity in fly visual circuits
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Physiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Physiology.
2012 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, no 22, 8758-8763 p.Article in journal (Refereed) Published
Abstract [en]

In higher-order motion stimuli, the direction of object motion does not follow the direction of luminance change. Such stimuli could be generated by the wing movements of a flying butterfly and further complicated by its motion in and out of shadows. Human subjects readily perceive the direction of higher-order motion, although this stands in stark contrast to prevailing motion vision models. Flies and humans compute motion in similar ways, and because flies behaviorally track bars containing higher-order motion cues, they become an attractive model system for investigating the neurophysiology underlying higher-order motion sensitivity. We here use intracellular electrophysiology of motion-vision-sensitive neurons in the hoverfly lobula plate to quantify responses to stimuli containing higher-order motion. We show that motion sensitivity can be broken down into two separate streams, directionally coding for elementary motion and figure motion, respectively, and that responses to Fourier and theta motion can be predicted from these. The sensitivity is affected both by the stimulus' time course and by the neuron's underlying receptive field. Responses to preferred-direction theta motion are sexually dimorphic and particularly robust along the visual midline.

Place, publisher, year, edition, pages
2012. Vol. 109, no 22, 8758-8763 p.
Keyword [en]
elementary motion detector, neural delays, sexual dimorphism, bar motion
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-176824DOI: 10.1073/pnas.1203081109ISI: 000304881700079OAI: oai:DiVA.org:uu-176824DiVA: diva2:537696
Available from: 2012-06-27 Created: 2012-06-26 Last updated: 2014-04-29Bibliographically approved
In thesis
1. Motion Vision Processing in Fly Lobula Plate Tangential Cells
Open this publication in new window or tab >>Motion Vision Processing in Fly Lobula Plate Tangential Cells
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Flies are highly visually guided animals. In this thesis, I have used hoverflies as a model for studying motion vision. Flies process motion vision in three visual ganglia: the lamina, the medulla, and the lobula complex. In the posterior part of lobula complex, there are around 60 lobula plate tangential cells (LPTCs). Most of LPTCs have large receptive fields where the local direction sensitivity suggests that they function as matched filters to specific types of optic flow. LPTCs connect to descending or neck motor neurons that control wing and head movements, respectively. Therefore, in this thesis I have focused on the electrophysiological responses of LPTCs to gain understanding of visual behaviors in flies.

The elementary motion detector (EMD) is a model that can explain the formation of local motion sensitivity. However, responses to higher order motion, where the direction of luminance change is uncorrelated with the direction of movement, cannot be predicted by classic EMDs. Nevertheless, behavior shows that flies can see and track bars with higher order motion cues. I showed (Paper I) that several LPTCs also respond to higher order motion.

Many insects, including flies, release octopamine during flight. Therefore, adding octopamine receptor agonists can mimic physical activity. Our study (Paper II) investigated the effect of octopamine on three adaptation components. We found that the contrast gain reduction showed a frequency dependent increase after octopamine stimulation. Since the contrast gain is non-directional, it is likely presynaptic to the LPTC. We therefore believe that octopamine acts on the delay filter in the EMD.

In the third paper we describe a novel LPTC. The centrifugal stationary inhibited flicker excited (cSIFE) is excited by flicker and inhibited by stationary patterns. Neither of these responses can be predicted by EMD models. Therefore, we provide a new type of motion detector that can explain cSIFE’s responses (Paper III).

During bar tracking, self-generated optic flow may counteract the steering effect by inducing a contradictory optomotor response. Behavior shows that during bar fixation, flies ignore background optic flow. Our study (Paper IV) focus on the different receptive fields of two LPTCs, and relate these to the bar fixation behavior. In the neuron with a small and fronto-dorsal receptive field, we find a higher correlation with bar motion than with background motion. In contrast, the neuron with a larger receptive field shows a higher correlation with background motion.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 47 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 984
hoverflies, EMD, higher order motion, octopamine, cSIFE, figure-ground discrimination, motion vision, lobula plate tangential cells
National Category
Biological Sciences
urn:nbn:se:uu:diva-220915 (URN)978-91-554-8908-3 (ISBN)
Public defence
2014-05-09, Museum Gustavianum, Uppsala, 13:15 (English)
Available from: 2014-04-17 Created: 2014-03-24 Last updated: 2014-04-29

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