Purchase this article with an account.
J. J. Kremers, A. Jünemann, B. Link; An Electroretinographical (ERG) Correlate of Parvocellular Activity. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1515.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The ERG mainly reflects activity in the outer retina. It is the purpose of the present work to find electroretinographical correlates of postreceptoral retinal mechanisms. For 30 Hz stimuli, the outer retina driven ERG responses are minimal when the L- and M-cones are modulated in counterphase. Decreasing the temporal frequency may therefore reveal responses originating in postreceptoral mechanisms.
ERG recordings were performed in 13 color normal subjects using square wave modulating stimuli displayed on a computer controlled color monitor. The stimuli isolated the responses of either the L- or the M-cones or stimulated them simultaneously (in phase and in counterphase) at various strengths. The rods were not stimulated in any of the conditions. The recordings were repeated at 12, 18, 24 and 30 Hz.
At 30 Hz the ratio between L- and M-cone driven ERG signal strengths was on average 3.75:1 and varied substantially between different subjects. The mean phase difference between the L- and M-cone driven signals was on average 106° (±59°). For conditions in which the L- or M-cones were isolated or the two were modulated in counterphase the ratio of L- to M-cone driven signal strengths decreased with decreasing temporal frequency. For 12 Hz stimuli the ratio was about 1.07:1 for all subjects. In the same conditions, the phase difference between L- and M-cone driven signals increased with decreasing temporal frequency and was about 171° (±20°) at 12 Hz, indicating that L- and M-cone driven signals interact antagonistically. When the cones are modulated in phase, a different mechanism seems to drive the ERGs.
The 12 Hz ERGs using stimuli in which cone responses were isolated or modulated simultaneously in counterphase showed a compelling correlation with properties of the parvocellular pathway (antagonistic activity of the L- and the M-cone driven signals; L/M ratios of about unity for all subjects independent of the L/M ratio at 30 Hz; less variability in L/M ratio and phase difference than at 30 Hz). We conclude that using these stimuli the ERG may reflect postreceptoral parvocellular activity.
This PDF is available to Subscribers Only