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A five-primary photostimulator suitable for studying intrinsically photosensitive retinal ganglion cell functions in humans

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journal contribution
posted on 16.05.2016, 00:00 authored by D. Cao, N. Nicandro, P.A. Barrionuevo
Intrinsically photosensitive retinal ganglion cells (ipRGCs) can respond to light directly through self-contained photopigment, melanopsin. IpRGCs also receive synaptic inputs from rods and cones. Thus, studying ipRGC functions requires a novel photostimulating method that can account for all of the photoreceptor inputs. Here, we introduced an inexpensive LED-based five-primary photostimulator that can control the excitations of rods, S-, M-, L-cones, and melanopsin-containing ipRGCs in humans at constant background photoreceptor excitation levels, a critical requirement for studying the adaptation behavior of ipRGCs with rod, cone, or melanopsin input. We described the theory and technical aspects (including optics, electronics, software, and calibration) of the five-primary photostimulator. Then we presented two preliminary studies using the photostimulator we have implemented to measure melanopsin-mediated pupil responses and temporal contrast sensitivity function (TCSF). The results showed that the S-cone input to pupil responses was antagonistic to the L-, M- or melanopsin inputs, consistent with an S-OFF and (L + M)-ON response property of primate ipRGCs (Dacey et al., 2005). In addition, the melanopsin-mediated TCSF had a distinctive pattern compared with L + M or S-cone mediated TCSF. Other than controlling individual photoreceptor excitation independently, the five-primary photostimulator has the flexibility in presenting stimuli modulating any combination of photoreceptor excitations, which allows researchers to study the mechanisms by which ipRGCs combine various photoreceptor inputs.

Funding

This study was supported by grants from IBRO John G. Nicholls Research Fellowship (PAB), Cless Family Foundation, and UIC core grant for vision research P30-EY01792, Unrestricted Departmental Grant from the Research to Prevent Blindness. We thank Drs. Joel Pokorny and Paul Gamlin for their comments on this manuscript.

History

Publisher Statement

This is a copy of an article published in the Journal of Vision © 2015 Association for Research in Vision and Ophthalmology Publications.

Publisher

Association for Research in Vision and Ophthalmology

issn

1534-7362

Issue date

26/01/2015

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