Cortical visual prostheses: from microstimulation to functional percept

Abstract

Cortical visual prostheses are intended to restore vision by targeted electrical stimulation of the visual cortex. The perception of spots of light, called phosphenes, resulting from microstimulation of the visual pathway, suggests the possibility of creating meaningful percept made of phosphenes. However, to date electrical stimulation of V1 has still not resulted in perception of phosphenated images that goes beyond punctate spots of light. In this review, we summarize the clinical and experimental progress that has been made in generating phosphenes and modulating their associated perceptual characteristics in human and macaque primary visual cortex (V1). We focus specifically on the effects of different microstimulation parameters on perception and we analyse key challenges facing the generation of meaningful artificial percepts. Finally, we propose solutions to these challenges based on the application of supervised learning of population codes for spatial stimulation of visual cortex.

Residual vision activation and the brain-eye-vascular triad: Dysregulation, plasticity and restoration in low vision and blindness – a review

“…Protecting, replacing or regenerating cells to restore vision is currently a very active research field. However, adequately summarizing this basic research field is beyond the scope of this review and readers should refer to other sources ( Fernandes, Diniz, Ribeiro & Humayun, 2012; Shepherd, Shivdasani, Nayagam, Williams & Blamey, 2013; Lewis & Rosenfeld, 2016; Rachitskaya & Yan, 2016; Bosking, Beauchamp & Yoshor, 2017; Cheng, Greenberg & Borton, 2017; Chun & Cestari, 2017; Benowitz, He & Goldberg, 2017; Calkins, Pekny, Cooper & Benowitz, 2017; Pardue & Allen 2018; Najarpour Foroushani, Pack & Sawan, 2018 ). Briefly, clinical trials on axonal regeneration, though promising experimentally, have not been carried out due to the still too limited regeneration potential ( de Lima, Habboub & Benowitz, 2012 ).…”

“…; Merabet, 2011; Hadjinicolaou, Meffin, Maturana, Cloherty & Ibbotson, 2015 ) have hampered early efforts. But new technological advancements such as electrode design and image processing have generated renewed interest in this approach ( Bosking et al, 2017; Najarpour Foroushani et al, 2018 ) and clinical trials are in progress ( https://clinicaltrials.gov/ct2/show/NCT03344848 ).…”

Dynamic Stimulation of Visual Cortex Produces Form Vision in Sighted and Blind Humans

“…In most participants with acquired blindness, only the eyes or optic nerves are damaged. This has inspired hope for the development of a visual cortical prosthetic (VCP), a device that would bypass the eyes and optic nerve, transmitting visual information from a camera directly into the visual cortex (Bosking et al, 2017a;Brindley and Lewin, 1968;Christie et al, 2016;Lewis et al, 2015Lewis et al, , 2016Najarpour Foroushani et al, 2018;Normann et al, 2009). VCPs rely on the fact that stimulating the visual cortex with electrical current can produce a percept of a small flash of light, known as a phosphene (Penfield and Rasmussen, 1950).…”

Injecting Information into the Mammalian Cortex: Progress, Challenges, and Promise

“…To provide a stable visual scene, therefore, biomimetic stimulation in the primary visual cortex may require additional stimulation that somehow engages the scene-stabilizing network. Furthermore, although one might think that simultaneous stimulation at multiple points selected to approximate a shape (e.g., a circle) would evoke the visual percept of the appropriate shape immediately, instead subjects initially perceive multiple separate phosphenes (Najarpour Foroushani and others 2018). Interestingly, interleaved ICMS pulses on nearby electrodes can produce the percept of a single fused shaped (Bak and others 1990), so it may be the well-known phenomenon of surround inhibition that creates separate phosphenes when pulses are delivered simultaneously (Tanaka and others 2019).…”