June 2021
Volume 62, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2021
Temporal relationship between ERG waveforms and the firing patterns of rat retinal ganglion cells
Author Affiliations & Notes
  • Nicholas Johnson
    Molecular Physiology and Pharmacology, USF Health Morsani College of Medicine, Tampa, Florida, United States
  • Youssef Mohamed
    Medical Engineering, University of South Florida College of Engineering, Tampa, Florida, United States
  • Christopher L Passaglia
    Medical Engineering, University of South Florida College of Engineering, Tampa, Florida, United States
  • Footnotes
    Commercial Relationships   Nicholas Johnson, None; Youssef Mohamed, None; Christopher Passaglia, None
  • Footnotes
    Support  NIH Grant EY027037-04
Investigative Ophthalmology & Visual Science June 2021, Vol.62, 623. doi:
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      Nicholas Johnson, Youssef Mohamed, Christopher L Passaglia; Temporal relationship between ERG waveforms and the firing patterns of rat retinal ganglion cells. Invest. Ophthalmol. Vis. Sci. 2021;62(8):623.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : The contribution of retinal ganglion cell (RGC) activity to noninvasive measures of retinal health such as the electroretinogram (ERG) is a topic of clinical interest. We simultaneously recorded RGC spike trains and the full-field ERG for various stimulus paradigms to directly determine how ERG waveforms relate to the timing and pattern of activity in different RGC types.

Methods : Adult Brown Norway rats were kept at an anesthetic plane under a mixture of ketamine and xylazine. A craniotomy was performed at Bregma and a tungsten-in-glass electrode was advanced into the optic nerve to record the RGC spike trains. A gold ring electrode was placed on the limbus of the eye to record the ERG. Visual stimuli consisted of full-field flashes (10 – 500ms duration) of light (0.018 – 1800 cd/m2/s) or darkness (1.8 cd/m2/s background) and full-field flicker (4 – 64 Hz) of 0.5 – 2 s duration presented via an LED-illuminated Ganzfeld dome. Tetrodotoxin (TTX; 6µM) was used to block spiking activity.

Results : Spike trains from ON RGCs cluster into ‘spike volleys’ that correspond to oscillatory potentials in the ERG to bright flashes (n=15; R2>0.95, p<0.05). Under these conditions, spike trains from OFF cells do not cluster into volleys but fire during the descending phase of the b-wave. Dark flashes produce a weak negative ERG wave analogous to the b-wave (n=6). Spike trains from OFF RGCs occur near the peak of the negative wave. The first harmonic amplitude of ON-transient (n=1) and OFF transient (n=9) RGC responses differed for short-duration flicker (p<0.05) but not for long-duration flicker. It did not differ for either short- or long-duration flicker for ON sustained (n=14) and OFF sustained (n=3) RGCs. TTX altered the ERG but did not eliminate OPs. Furthermore, cross correlation between the spontaneous activity of RGCs and the ERG did not reveal significant correlation (n=9).

Conclusions : OP generators in the retina drive oscillatory spike patterns in RGCs. Contrary to prior studies, there were no significant differences in the flicker responses of ON- and OFF-pathways.

This is a 2021 ARVO Annual Meeting abstract.

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