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The Journal of Neuroscience, December 20, 2006, 26(51):13250-13263; doi:10.1523/JNEUROSCI.1991-06.2006

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Behavioral/Systems/Cognitive
Local Edge Detectors: A Substrate for Fine Spatial Vision at Low Temporal Frequencies in Rabbit Retina

Michiel van Wyk,¹ W. Rowland Taylor,² and David I. Vaney¹

¹Vision, Touch and Hearing Research Centre, School of Biomedical Sciences, Australian Research Council Centre of Excellence in Vision Science, University of Queensland, Brisbane, Queensland 4072, Australia, and ²Neurological Sciences Institute, Oregon Health & Science University, Beaverton, Oregon 97006

Correspondence should be addressed to Prof. David I. Vaney, Vision, Touch and Hearing Research Centre, The University of Queensland, Brisbane, Queensland 4072, Australia. Email: d.vaney{at}uq.edu.au

Visual acuity is limited by the size and density of the smallest retinal ganglion cells, which correspond to the midget ganglion cells in primate retina and the ß-ganglion cells in cat retina, both of which have concentric receptive fields that respond at either light-On or light-Off. In contrast, the smallest ganglion cells in the rabbit retina are the local edge detectors (LEDs), which respond to spot illumination at both light-On and light-Off. However, the LEDs do not predominate in the rabbit retina and the question arises, what role do they play in fine spatial vision? We studied the morphology and physiology of LEDs in the isolated rabbit retina and examined how their response properties are shaped by the excitatory and inhibitory inputs. Although the LEDs comprise only 15% of the ganglion cells, neighboring LEDs are separated by 30–40 µm on the visual streak, which is sufficient to account for the grating acuity of the rabbit. The spatial and temporal receptive-field properties of LEDs are generated by distinct inhibitory mechanisms. The strong inhibitory surround acts presynaptically to suppress both the excitation and the inhibition elicited by center stimulation. The temporal properties, characterized by sluggish onset, sustained firing, and low bandwidth, are mediated by the temporal properties of the bipolar cells and by postsynaptic interactions between the excitatory and inhibitory inputs. We propose that the LEDs signal fine spatial detail during visual fixation, when high temporal frequencies are minimal.

Key words: retinal ganglion cell; edge detection; rabbit retina; visual acuity; amacrine cell; inhibition

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Received May 10, 2006; revised Nov. 3, 2006; accepted Nov. 8, 2006.

Correspondence should be addressed to Prof. David I. Vaney, Vision, Touch and Hearing Research Centre, The University of Queensland, Brisbane, Queensland 4072, Australia. Email: d.vaney{at}uq.edu.au

This article has been cited by other articles:

				D. J. Calkins and P. Sterling Microcircuitry for Two Types of Achromatic Ganglion Cell in Primate Fovea J. Neurosci., March 7, 2007; 27(10): 2646 - 2653. [Abstract] [Full Text] [PDF]

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