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Development of visual Neuroprostheses: trends and challenges.

ABSTRACT: Visual prostheses are implantable medical devices that are able to provide some degree of vision to individuals who are blind. This research field is a challenging subject in both ophthalmology and basic science that has progressed to a point where there are already several commercially available devices. However, at present, these devices are only able to restore a very limited vision, with relatively low spatial resolution. Furthermore, there are still many other open scientific and technical challenges that need to be solved to achieve the therapeutic benefits envisioned by these new technologies. This paper provides a brief overview of significant developments in this field and introduces some of the technical and biological challenges that still need to be overcome to optimize their therapeutic success, including long-term viability and biocompatibility of stimulating electrodes, the selection of appropriate patients for each artificial vision approach, a better understanding of brain plasticity and the development of rehabilitative strategies specifically tailored for each patient.

SUBMITTER: Fernandez E

PROVIDER: S-EPMC7098238 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Development of visual Neuroprostheses: trends and challenges.

Fernandez Eduardo E

Bioelectronic medicine 20180813

Visual prostheses are implantable medical devices that are able to provide some degree of vision to individuals who are blind. This research field is a challenging subject in both ophthalmology and basic science that has progressed to a point where there are already several commercially available devices. However, at present, these devices are only able to restore a very limited vision, with relatively low spatial resolution. Furthermore, there are still many other open scientific and technical ...[more]

PMID: 32232088

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Project description:Microelectrode arrays implanted in the brain are increasingly used for the research and treatment of intractable neurological disease. However, local neuronal loss and glial encapsulation are known to interfere with effective integration and communication between implanted devices and brain tissue, where these observations are typically based on assessments of broad neuronal and astroglial markers. However, both neurons and astrocytes comprise heterogeneous cellular populations that can be further divided into subclasses based on unique functional and morphological characteristics. In this study, we investigated whether or not device insertion causes alterations in specific subtypes of these cells. We assessed the expression of both excitatory and inhibitory markers of neurotransmission (vesicular glutamate and GABA transporters, VGLUT1 and VGAT, respectively) surrounding single-shank Michigan-style microelectrode arrays implanted in the motor cortex of adult rats by use of quantitative immunohistochemistry. We found a pronounced shift from significantly elevated VGLUT1 within the initial days following implantation to relatively heightened VGAT by the end of the 4-wk observation period. Unexpectedly, we observed VGAT positivity in a subset of reactive astrocytes during the first week of implantation, indicating heterogeneity in early-responding encapsulating glial cells. We coupled our VGLUT1 data with the evaluation of a second marker of excitatory neurons (CamKii?); the results closely paralleled each other and underscored a progression from initially heightened to subsequently weakened excitatory tone in the neural tissue proximal to the implanted electrode interface (within 40 ?m). Our results provide new evidence for subtype-specific remodeling surrounding brain implants that inform observations of suboptimal integration and performance.NEW & NOTEWORTHY We report novel changes in the local expression of excitatory and inhibitory synaptic markers surrounding microelectrode arrays implanted in the motor cortex of rats, where a progressive shift toward increased inhibitory tone was observed over the 4-wk observation period. The result was driven by declining glutamate transporter expression (VGLUT1) in parallel with increasing GABA transporter expression (VGAT) over time, where a reactive VGAT+ astroglial subtype made an unexpected contribution to our findings.

Project description:Background and objectivesThe National Health and Aging Trends Study (NHATS) is an ongoing, nationally representative panel study of older adults that collects data on health and disability, including measures on self-reported visual disability (SRVD). Prior studies assessing the association of SRVD with other measures of healthy aging have classified participants as having or not having SRVD, which does not capture the full spectrum of SRVD reported by participants. Therefore, we sought to develop and validate an ordinal indicator of SRVD to facilitate research on the impact of late-life SRVD on health and disability in NHATS.Research design and methodsWe used 2015 NHATS data with community-dwelling participants who answered survey questions about visual functioning and vision aid use. Based on responses, participants were categorized into one of 6 groups: blind, near and distance SRVD without vision aid use, near and distance SRVD with vision aid use, near or distance SRVD without vision aid use, near or distance SRVD with vision aid use, or no SRVD. Multivariable Poisson regression models assessed convergent validity of the ordinal SRVD scale with functional activity and well-being scores, while adjusting for demographic factors and medical comorbidities.ResultsOf the 7061 eligible individuals, 8.3% (n = 742) reported SRVD. Using our novel ordinal indicator of SRVD in NHATS, higher levels of SRVD were significantly associated with lower functional activity scores (p < .001 for all) and subjective well-being (p < .001), except for participants reporting blindness. Significant differences between SRVD groups were found, which could not be captured using a binary SRVD variable.Discussion and implicationsA novel 6-level SRVD scale in NHATS demonstrated convergent validity with functional activity and well-being scales. This scale provides a new tool with improved measurement precision to study the impact of late-life SRVD on health and disability in a nationally representative study of older adults.

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Development of visual Neuroprostheses: trends and challenges.

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Development of visual Neuroprostheses: trends and challenges.

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