Photovoltaic restoration of sight with high visual acuity

Patients with retinal degeneration lose sight due to the gradual demise of photoreceptors. Electrical stimulation of surviving retinal neurons provides an alternative route for the delivery of visual information. We demonstrate that subretinal implants with 70-μm-wide photovoltaic pixels provide highly localized stimulation of retinal neurons in rats. The electrical receptive fields recorded in retinal ganglion cells were similar in size to the natural visual receptive fields. Similarly to normal vision, the retinal response to prosthetic stimulation exhibited flicker fusion at high frequencies, adaptation to static images and nonlinear spatial summation. In rats with retinal degeneration, these photovoltaic arrays elicited retinal responses with a spatial resolution of 64 ± 11 μm, corresponding to half of the normal visual acuity in healthy rats. The ease of implantation of these wireless and modular arrays, combined with their high resolution, opens the door to the functional restoration of sight in patients blinded by retinal degeneration

Recruitment of upper-limb motoneurons with epidural electrical stimulation of the cervical spinal cord.

Epidural electrical stimulation (EES) of lumbosacral sensorimotor circuits improves leg motor control in animals and humans with spinal cord injury (SCI). Upper-limb motor control involves similar circuits, located in the cervical spinal cord, suggesting that EES could also improve arm and hand movements after quadriplegia. However, the ability of cervical EES to selectively modulate specific upper-limb motor nuclei remains unclear. Here, we combined a computational model of the cervical spinal cord with experiments in macaque monkeys to explore the mechanisms of upper-limb motoneuron recruitment with EES and characterize the selectivity of cervical interfaces. We show that lateral electrodes produce a segmental recruitment of arm motoneurons mediated by the direct activation of sensory afferents, and that muscle responses to EES are modulated during movement. Intraoperative recordings suggested similar properties in humans at rest. These modelling and experimental results can be applied for the development of neurotechnologies designed for the improvement of arm and hand control in humans with quadriplegia

Photovoltaic restoration of high visual acuity in rats with retinal degeneration

Patients with retinal degeneration lose sight due to gradual demise of photoreceptors. Electrical stimulation of the surviving retinal neurons provides an alternative route for delivery of visual information. We developed subretinal photovoltaic arrays to convert pulsed light into bi-phasic pulses of current to stimulate the nearby inner retinal neurons. Bright pulsed illumination is provided by image projection from video goggles and avoids photophobic effects by using near-infrared (NIR, 880-915nm) light. Experiments in-vitro and in-vivo demonstrate that the network-mediated retinal stimulation preserves many features of natural vision, such as flicker fusion, adaptation to static images, and most importantly, high spatial resolution. Our implants with 70μm pixels restored visual acuity to half of the normal level in rats with retinal degeneration. Ease of implantation and tiling of these wireless arrays to cover a large visual field, combined with their high resolution opens the door to highly functional restoration of sight