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Comparison of modulation efficiency between normal and degenerated primate retina
Yongseok Yoo1, Seongkwang Cha2, Yong Sook Goo2,3
1School of Computer Science and Engineering, Soongsil University, Seoul, Republic of Korea.
Frontiers in Cell and Developmental Biology
|August 15, 2024
Summary
Electrical stimulation of retinal ganglion cells (RGCs) is key for prostheses. In degenerated retinas, shorter intervals between RGC spikes reduce stimulation effectiveness, impacting device calibration.
Area of Science:
- Neuroscience
- Biomedical Engineering
- Ophthalmology
Background:
- Retinal prostheses aim to restore vision by electrically stimulating retinal ganglion cells (RGCs), bypassing damaged photoreceptors.
- Effective RGC modulation is critical for prosthesis efficacy, but stimulus-response variability complicates development.
- Understanding factors influencing RGC response to electrical stimulation is essential for optimizing retinal prostheses.
Purpose of the Study:
- To identify an indicator for effective electrical stimulation of RGCs.
- To investigate how internal and external variables influence RGC response in normal versus degenerated primate retinas.
- To establish relationships between stimulation parameters and the modulation efficiency ratio (MER).
Main Methods:
- Used six cynomolgus monkeys, with three serving as controls and three in an N-methyl-N-nitrosourea (MNU)-induced retinal degeneration model.
- Recorded retinal activity using 8x8 multi-electrode arrays (MEAs) during electrical stimulation with biphasic pulses.
- Defined Modulation Efficiency Ratio (MER) as the proportion of stimulation conditions eliciting significantly higher post-stimulation firing rates than pre-stimulus rates.
Main Results:
- MER was significantly lower in degenerated retinas compared to normal retinas.
- External variables (duration, inter-electrode distance) affected MER similarly in both groups.
- Internal variables (spontaneous firing rate statistics) showed differential effects: mean inter-spike interval (ISI) positively correlated with MER in degenerated retinas, while CV of ISIs negatively correlated.
Conclusions:
- Hyperactive firing (shorter mean ISI) in degenerated retinas reduces the effectiveness of electrical stimulation, leading to lower MER.
- Internal firing statistics of RGCs are critical for understanding stimulation efficacy in retinal degeneration.
- Findings provide insights for optimizing stimulation channel selection and calibration methods for retinal prostheses.
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