The motion after-effect: local and global contributions to contrast sensitivity.

Karin Nordström,David C O'Carroll

doi:10.1098/rspb.2008.1932

Karin Nordström, David C O'Carroll

Open Access

https://doi.org/10.1098/rspb.2008.1932

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Abstract

Motion adaptation is a widespread phenomenon analogous to peripheral sensory adaptation, presumed to play a role in matching responses to prevailing current stimulus parameters and thus to maximize efficiency of motion coding. While several components of motion adaptation (contrast gain reduction, output range reduction and motion after-effect) have been described, previous work is inconclusive as to whether these are separable phenomena and whether they are locally generated. We used intracellular recordings from single horizontal system neurons in the fly to test the effect of local adaptation on the full contrast-response function for stimuli at an unadapted location. We show that contrast gain and output range reductions are primarily local phenomena and are probably associated with spatially distinct synaptic changes, while the antagonistic after-potential operates globally by transferring to previously unadapted locations. Using noise analysis and signal processing techniques to remove ‘spikelets’, we also characterize a previously undescribed alternating current component of adaptation that can explain several phenomena observed in earlier studies.

Highlights

Sensory neurons and systems adapt to prolonged stimulation
Hoverflies differ from blowflies in their visual ecology, and recent work shows interesting sexual dimorphism of these neurons not found in Calliphora ( Nordstrom et al 2008), motion adaptation and underlying temporal coding is highly consistent across lobula plate tangential cells (LPTCs) and dipteran species
Other studies suggest that motion adaptation in horizontal system (HS) and H1 in Eristalis and Calliphora is comparable (Borst & Egelhaaf 1987; Harris & O’Carroll 2002) and even Drosophila LPTCs code motion to larger flies ( Joesch et al 2008)

Summary

Introduction

Sensory neurons and systems adapt to prolonged stimulation. Such dependence on stimulus history matches neural sensitivity and response properties to the strength and statistics of current stimulus parameters. The second component, the antagonistic after-potential, is larger following preferred than anti-preferred direction adaptation (Harris et al 2000; Kohn & Movshon 2003) and either originates in the motion neurons themselves (Kurtz 2007) or at earlier processing stages.

Results

Conclusion