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Published on: June 9, 2015
Origin of the fast oscillation in the electroretinogram of the macaque
Abstract:
To investigate the origin of the fast oscillation, a phenomenon in the electroretinogram evoked with stimulus frequencies of about 8 mHz (a period time of about 2 min), we recorded responses from retina and pigment epithelium in the macaque. Micropipettes were placed in the subretinal space and in the vitreous close to the retina; the reference electrode was in the orbit behind the eye. Thus, simultaneous recordings were obtained of the trans-epithelial, the trans-retinal and the trans-tissue (vitreal) potential. At 10 mHz the trans-retinal and the trans-epithelial responses are of about equal magnitude but of opposite phase, resulting in a small and rather variable vitreal potential. The origin of the fast oscillation evoked with repetitive stimuli lies in subtle differences between retinal and pigment epithelial potentials, in which a pigment epithelial event plays an important role. For single stimuli lasting 60 s again the trans-epithelial and trans-retinal responses were of equal magnitude and opposite polarity. The epithelial responses were found to return more quickly towards the baseline than the retinal responses. In vitreal recordings this causes a trough between the c-wave and the light peak which is referred to as the "trough" fast oscillation. Most of the "trough" fast oscillation is caused by a pigment epithelial event. In view of the complexity of the fast oscillation evoked with repetitive stimuli it might be difficult to relate pathology to specific neuro-epithelial structures.
Insights
The fast oscillation in electroretinograms originates from subtle differences between retinal and pigment epithelial potentials. Pigment epithelial events significantly contribute to this phenomenon, particularly the "trough" oscillation observed in vitreal recordings.
Area of Science:
- Ophthalmology
- Neuroscience
- Physiology
Background:
- The electroretinogram (ERG) is a vital diagnostic tool for assessing retinal function.
- Fast oscillations in the ERG, occurring at frequencies around 8 mHz, have been observed but their origin remains unclear.
- Understanding these oscillations is crucial for interpreting ERG results in various ocular conditions.
Purpose of the Study:
- To investigate the origin of the fast oscillation phenomenon in the electroretinogram.
- To differentiate the contributions of retinal and pigment epithelial potentials to the fast oscillation.
- To elucidate the role of pigment epithelial events in generating specific components of the fast oscillation.
Main Methods:
- Simultaneous recordings of trans-epithelial, trans-retinal, and vitreal potentials in macaque eyes using micropipettes.
- Stimulation at frequencies of approximately 8-10 mHz and single stimuli of 60s duration.
- Analysis of the phase and magnitude of responses from different retinal layers.
Main Results:
- Trans-retinal and trans-epithelial responses were of equal magnitude and opposite phase at 10 mHz.
- A pigment epithelial event plays a significant role in the origin of the fast oscillation, especially the "trough" oscillation.
- Epithelial responses returned to baseline faster than retinal responses, creating the observed trough between the c-wave and light peak.
Conclusions:
- The fast oscillation in the electroretinogram arises from subtle differences between retinal and pigment epithelial potentials.
- Pigment epithelial activity is a key contributor to the fast oscillation, particularly the "trough" component.
- The complexity of fast oscillations may complicate the correlation of pathology with specific neuro-epithelial structures.
