Chronically implanted epidural electrodes in Göttinger minipigs allow function tests of epiretinal implants

Area of Science:

• Neuroscience
• Biomedical Engineering
• Ophthalmology

Background:

• Assessing implantable retinal stimulation devices requires long-term cortical potential recordings.
• Minipig frontal sinus anatomy makes skin electrodes unsuitable for representative recordings.
• Epidural electrodes were implanted in minipigs for chronic testing.

Purpose of the Study:

• To describe long-term recordings of electrically evoked cortical potentials in minipigs.
• To evaluate the efficacy of epidural electrodes for monitoring retinal implant function.
• To validate the minipig model for retinal implant research.

Main Methods:

• Silver-silver chloride epidural electrodes were implanted dorsal to the visual cortex in Göttinger minipigs.
• Visual and electrical retinal stimulation were applied using light and implanted multielectrode arrays.
• Cortical potentials were recorded following stimulation with biphasic charge-balanced currents.

Main Results:

• Epidural electrodes allowed recording of visual cortex potentials for up to 18 months.
• Stable electrode location and recording properties were indicated by consistent response amplitudes.
• Electrical retinal stimulation evoked cortical responses with less delay than visual stimulation, with a threshold of 50 microA.

Conclusions:

• The minipig model is suitable for implanting epiretinal stimulation electrodes.
• Chronic epidural electrode recordings effectively monitor cortical responses to retinal implants.
• This model supports long-term testing of retinal implant functionality.