Adaptive changes of inner retina function in response to sustained pattern stimulation

Abstract

We have characterized adaptive changes of inner retina function in response to sustained pattern stimulation in 32 normal subjects with an age range 23 to 77 years by measuring changes of the pattern electroretinogram (PERG) as a function of time. Contrast-reversal stimuli had square-wave profile in space and time, with peak spatial and temporal frequency and high contrast to maximize response amplitude. The PERG signal was sampled over 5 minutes with a resolution of 15 s. PERG signals were non-stationary, resulting in either progressive amplitude decline or even enhancement to a plateau, with a time course that could be well described by an exponential function with a time constant of 1-2 minutes. Higher initial amplitudes were generally associated with amplitude decline, and lower initial amplitudes with enhancement. The delta amplitude (plateau minus initial) was a linear function of the initial amplitude. The magnitude of delta decreased with decreasing initial amplitude and inverted its sign for initial amplitudes about 1/3 lower than the maximum initial amplitude measured, but still about 3-4 times larger than the noise. Amplitude decline was generally associated with phase lag, whereas amplitude enhancement was associated with phase advance. Altogether, PERG generators appear to slowly adjust their gain in order to keep their sustained activity at an intermediate level that is rather independent of the level of activity at stimulus onset. This behavior is reminiscent of a buffering mechanism, where glial cells may play a primary role. An energy budget model of neural-vascular-glial interaction is provided together with an equivalent electrical circuit that accounts for the results.

Next Generation PERG Method: Expanding the Response Dynamic Range and Capturing Response Adaptation

“…11 PERG adaptation provides specific physiological information on RGC function, 11,12 as it is selectively altered in diseases such as glaucoma 31 and optic neuritis. 21 To explore the response dynamic range and intrinsic variability over a wide range of conditions relevant to clinical application, we investigated the PERGx method in different groups of subjects including younger normal controls, older normal controls, open-angle glaucoma patients with modest visual field defects, and NAION patients with severe visual field defects.…”

Efficiency and Safety of AAV-Mediated Gene Delivery of the Human ND4 Complex I Subunit in the Mouse Visual System

“…It shortened the PERG latency. Amplitude and phase represent two distinct aspects of neural activity 18-20. Response amplitude is related to the number and vitality of retinal neurons contributing to the recorded electrical signal.…”

Adaptation of the Steady-state PERG in Early Glaucoma

“…Forty-two subjects were suspected of having glaucoma (GS, n=42, mean age 54.9±10.7 years); twenty-two had early manifest glaucoma (EMG, n=22, mean age 60.3 ±10.2 years), and sixteen were normal controls (NC, n=16; mean age 52.7 ±12.8 years) from a previous study. 7 No control subject had family history of glaucoma, suspicious glaucomatous optic disk, or IOP> 16 mm Hg. The mean ages of the groups were not significantly different (ANOVA, P=0.082).…”

“…Recently, it has been shown that the steady-state pattern electroretinogram (PERG) recorded during continuous presentation of fast-reversing, high-contrast, fine gratings displays slow adaptive changes of the response amplitude that have been interpreted as metabolic adaptation. 6, 7 In contrast, the flicker ERG — a measure of outer retina function — remains unchanged during continuous presentation of a luminance-modulated uniform field. 8 Altogether, these results imply that fast contrast-reversing patterns induce adaptive functional changes in the inner, but not outer, retina in response to changed metabolic requirements.…”