Responses of primate retinal ganglion cells to perimetric stimuli.
OBJECTIVE
Perimetry is used clinically to assess glaucomatous ganglion cell loss. It has been proposed that frequency-doubling stimuli are better than the conventional size III perimetric stimulus in preferentially stimulating magnocellular (M) versus parvocellular (P) ganglion cells. However, little is known about how primate ganglion cells respond to perimetric stimuli. The authors recorded contrast responses of M and P ganglion cells to size III and frequency-doubling stimuli and compared contrast gain of M and P cells to these stimuli to assess the ability of these stimuli to preferentially stimulate M versus P cells.


METHODS
Data were recorded from 69 macaque retinal ganglion cells, by an in vivo preparation, at eccentricities of 5° to 15°. The size III stimulus was a circular luminance increment 26 min arc in diameter, 200 ms in duration. The frequency-doubling stimulus was a sinusoidal grating (0.5 cyc/deg) temporally modulated in counterphase at 13 Hz. A Michaelis-Menten function was fit to each cell's contrast responses to assess contrast gain.


RESULTS
For both size III and frequency-doubling stimuli, ganglion cell responses increased linearly at low contrasts, and then the increase slowed at high contrasts (saturation). The mean (± SE) difference in estimated log contrast gain between M and P cells for the size III stimulus was significantly higher than that for the frequency-doubling stimulus (1.24 ± 0.09 vs. 0.89 ± 0.13; P < 0.01).


CONCLUSIONS
The size III stimulus was superior to the frequency-doubling stimulus in preferentially stimulating M cells versus P cells.
Swanson
William H
WH
School of Optometry, Indiana University, Bloomington, Indiana 47405-3680, USA. wilswans@indiana.edu
Sun
Hao
H
Lee
Barry B
BB
Cao
Dingcai
D
D000818:Animals; D015350:Contrast Sensitivity / Q000502:physiology*; D008252:Macaca fascicularis; D010775:Photic Stimulation; D012165:Retinal Ganglion Cells / Q000502:physiology* / Q000528:radiation effects*; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology*