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Intrinsic cone adaptation modulates feedback efficiency from horizontal cells to cones
I Fahrenfort1, R L Habets, H Spekreijse
1Graduate School Neurosciences Amsterdam, The Netherlands Ophthalmic Research Institute, 1105 BA Amsterdam, The Netherlands.
The Journal of General Physiology
|September 25, 1999
Summary
Light adaptation enhances retinal feedback efficiency by threefold. This occurs due to cone depolarization, increasing calcium current modulation and optimizing vision in changing light conditions.
Area of Science:
- Neuroscience
- Vision Science
- Retinal Physiology
Background:
- Retinal processing of visual stimuli changes significantly during light/dark adaptation.
- The feedback pathway from horizontal cells to cones is modulated during adaptation, but the underlying mechanism is poorly understood.
Purpose of the Study:
- To elucidate the mechanism behind the increased efficiency of the feedback synapse from horizontal cells to cones during light adaptation.
Main Methods:
- Investigated the effect of flash trains on horizontal cell feedback responses in cones.
- Measured cone membrane potential changes and calcium currents under adapted and unadapted conditions.
Main Results:
- A train of flashes increased feedback response up to threefold with a time constant of ~3 s, attributed to cone-intrinsic processes.
- Cone depolarization during flash adaptation enhanced light-induced calcium current changes and synaptic feedback efficiency.
- Observed changes in horizontal cell responses were fully explained by altered synaptic efficiency.
Conclusions:
- Cone depolarization during adaptation enhances the efficiency of negative feedback from horizontal cells.
- This mechanism optimizes retinal processing for ambient light conditions, impacting dynamic, spatial, and spectral processing.