Inhibitory Circuits Can Restore OFF Pathway Responses in Retinal Prostheses

Area of Science:

• Neuroscience
• Vision Science
• Biomedical Engineering

Background:

• Visual processing relies on parallel ON and OFF pathways for luminance changes.
• Current retinal prostheses activate the ON pathway but fail to engage the OFF pathway, limiting perception of dark features.
• Retinal degeneration diseases like retinitis pigmentosa severely impair vision by affecting these pathways.

Purpose of the Study:

• To investigate the functional deficits of the OFF pathway in a mouse model of retinitis pigmentosa.
• To identify cellular mechanisms and neural circuits responsible for electrically evoked OFF pathway responses.
• To explore strategies for improving prosthetic vision by targeting the OFF pathway.

Main Methods:

• Electrical stimulation of retinal ganglion cells (RGCs) in a mouse model of retinitis pigmentosa.
• Whole-cell voltage recordings to analyze RGC responses to stimulation.
• Combinatorial genetic and chemogenetic approaches to identify pre-synaptic sources.
• Investigating the role of hyperpolarization-activated cyclic nucleotide-gated channels.

Main Results:

• Most OFF RGCs exhibited aberrant ON responses to electrical stimulation.
• A specific subtype, OFFα RGCs, demonstrated preserved OFF responses post-stimulation.
• These preserved responses were mediated by post-inhibitory rebound excitation via specific ion channels.
• AII amacrine cells were identified as the pre-synaptic drivers of these OFF responses.

Conclusions:

• The OFFα RGC subtype and its underlying circuitry offer a potential target for restoring OFF pathway function.
• Understanding the mechanisms of post-inhibitory rebound excitation is crucial for prosthetic development.
• Tuning electrical stimulation parameters can enhance OFF pathway activation, improving prosthetic vision restoration.