Abstract
Purpose :
The ERG originates in the activity of retinal neurons and therefore can be considered to be an epiphenomenon of the neuronal visual responses. It was found previously that ERG responses to continuous stimulation are correlated with activity of major retinal pathways and with visual perception. In the present study, we tried to find a method to link psychophysical thresholds to ERG recordings.
Methods :
Psychophysical flicker detection thresholds were measured foveally (3° diameter) in three normal subjects to luminance stimulation with three temporal profiles: sine-wave, rapid-on sawteeth and rapid-off sawteeth. The temporal frequency was varied between 1 and 39 Hz. We measured full field ERGs to the same waveforms and temporal frequencies at 0, 3, 5, 10, 15 and 20% contrast in four normal subjects (total recording time for each condition: 80 sec). The ERG responses were averaged for all subjects and for a 1 sec episode. Then the ERGs were analyzed with a peak-to-trough detector (PTD) that integrated the ERG responses in two time windows that were shifted in time relative to each other. The two time windows were slid over the whole recording episode and subtracted to obtain the PDT output at each time instant. A root mean square (RMS) calculation was performed on the PTD output for the whole recording period to obtain the cumulative PDT response. Several time windows and shifts (difference between the two time windows) were used.
Results :
The response strength of the PTD increased with increasing contrast. Contrasts for a threshold PTD response could be defined. The thresholds strongly depended on the chosen PTD characteristics. With well-chosen PTD characteristics, the PTD thresholds for all stimuli resembled the psychophysical thresholds.
Conclusions :
Although the ERG is not the neuronal visual response that is transferred to the brain, it is assumed that it is uniquely related to the neuronal response (if the neuronal response is altered, the ERG is also altered; if the neuronal response is not changed, the ERG is not changed). With the PTD algorithm, the ERG can possibly be used as an objective tool to link retinal activity, elicited by continuous luminance waveforms, with psychophysical data.
This is a 2021 ARVO Annual Meeting abstract.