Toward Long-Term Communication With the Brain in the Blind by Intracortical Stimulation: Challenges and Future Prospects
Open accessAbstract
The restoration of a useful visual sense in a profoundly blind person by direct electrical stimulation of the visual cortex has been a subject of study for many years. However, the field of cortically based sight restoration has made few advances in the last few decades, and many problems remain. In this context, the scientific and technological problems associated with safe and effective communication with the brain are very complex, and there are still many unresolved issues delaying its development. In this work, we review some of the biological and technical issues that still remain to be solved, including long-term biotolerability, the number of electrodes required to provide useful vision, and the delivery of information to the implants. Furthermore, we emphasize the possible role of the neuroplastic changes that follow vision loss in the success of this approach. We propose that increased collaborations among clinicians, basic researchers, and neural engineers will enhance our ability to send meaningful information to the brain and restore a limited but useful sense of vision to many blind individuals.
AI snapshot
Written from the paper’s full text.
TL;DR
This review argues that intracortical microstimulation could restore limited but useful vision in blind individuals, but long-term biotolerability, electrode count, wireless data/power delivery, and visual encoding remain unresolved. It emphasizes neuroplasticity after vision loss and multidisciplinary collaboration as key to future progress.
Key findings
- Penetrating microelectrodes can stimulate visual cortex with much lower currents than surface electrodes: in a 100-electrode Utah array implanted in occipital cortex of a 57-year-old for six months, thresholds were 1–100 µA, two to three orders of magnitude lower than surface-electrode currents.
- Simulation/psychophysical estimates suggest ~625 electrodes at primary visual cortex might support reading (at lower speeds) and navigation, and ~600–700 electrodes might provide some functional vision, though this often implies tunnel vision; matching retinal output would require at least 1 million parallel channels (the retina has ~1–1.5 million ganglion cell axons per eye).
- Long-term biotolerability remains unresolved: all intracortical electrodes induce foreign-body/inflammatory responses and glial scarring, and most intracortical microelectrodes have a maximum in vivo lifetime of several months or a few years.
- Wireless devices with hundreds of electrodes face power/communication constraints, crosstalk, multiplexing, and fitting challenges; neuroplastic changes after blindness may affect prosthesis success and help define a preferred time window.
Methods
- Narrative review of biological and technical issues in intracortical visual prostheses, not a systematic review or primary experimental study.
- Draws on literature and authors’ prior/ongoing work; mentions a 100-electrode Utah array implanted in a 57-year-old for six months and a 10-minute human Utah array implantation shown in Figure 2.
- Main analysis is qualitative synthesis of challenges and future prospects; no meta-analysis or pooled quantitative analysis is reported.
Limitations
- Stated: many unresolved issues delay development; long-term biotolerability is unresolved; most intracortical microelectrodes last only months to a few years; how many electrodes are needed will likely only be addressable by future experiments in blind subjects; fitting hundreds or thousands of electrodes is not viable with current procedures.
- Stated: more experiments and studies are still needed for multiple arrays, wireless high-channel devices, stimulation optimization, and visual encoding.
- Evident: as a narrative review, it lacks systematic search/selection criteria and does not report primary outcomes beyond cited or mentioned preliminary work; no quantitative synthesis is provided.
Model-written summary. Check it against the paper before relying on it.
Integrity signals
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Cites
Statistics
Claims the paper makes
0 of 64 cited sources checked · 0 supported · 0 flagged
- Findingcitation
In a 57-year-old person implanted with an array of 100 penetrating electrodes (Utah Electrode Array) in the occipital cortex during a six-month period, stimulation thresholds to excite neurons were in the 1-100 microamp range.
“Thus, we recently implanted an array of 100 penetrating electrodes (a Utah Electrode Array) in the occipital cortex of a 57-year-old person during a six-month period, and we found that stimulation thresholds to excite neurons were in the 1-100 microamp range (Fernandez et al., 2019).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Fernandez et al., 2019
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- Findingreasoning
Microelectrodes become surrounded by many blood cells and plasma proteins that stick to their surface.
“Thus, the microelectrodes become surrounded by many blood cells and plasma proteins that stick to their surface. Figure 2 shows a representative example.”
Quote in the paperSubstantial claim - Premisecitation
Several retinal devices have already been approved for patients with retinal dystrophies.
“At present, retinal prostheses are the most successful approach in this field, and several retinal devices have already been approved for patients with retinal dystrophies (Da Cruz et al., 2016; Stingl et al., 2017).”
Quote in the paperSubstantial claim0 of 2 sources checked - Premisecitation
The concept of artificially producing a visual sense in the blind is based on current understanding of the structure of the mammalian visual system and the relationship between electrical stimulation of any part of the visual pathways and the resulting visual perceptions.
“The concept of artificially producing a visual sense in the blind is based on our current understanding of the structure of the mammalian visual system and the relationship between electrical stimulation of any part of the visual pathways and the resulting visual perceptions (Fernandez and Normann, 1995; Maynard, 2001).”
Quote in the paperSubstantial claim0 of 2 sources checked- cites Fernandez and Normann, 1995
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- cites Maynard, 2001 source
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- Interpretationown data
The stimulation thresholds with the penetrating array are two to three orders of magnitude smaller than the currents required to evoke phosphenes using surface electrodes.
“This is clearly two to three orders of magnitude smaller than the currents required to evoke phosphenes using surface electrodes.”
Quote in the paperSubstantial claim
- Premisereasoning
The FBR often starts with damage to blood vessels encountered during implantation, which causes small interstitial microhemorrhages.
“Often, the FBR starts with the damage to the blood vessels encountered during the implantation of the microelectrodes in the neural tissue (see Figure 1), which causes small interstitial microhemorrhages.”
Quote in the paperNot a substantial claim - Premisecitation
Mechanical micromovements between the pulsating neural tissue and static implants can induce different kinds of damage.
“In addition, we should also consider the mechanical micromovements between the pulsating neural tissue (due mainly to cardiac pulse and breathing) and the static implants, which can induce different kinds of damage (Polanco et al., 2016).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Polanco et al., 2016 source
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- Interpretationreasoning
A retinal prosthesis may not be useful in patients with advanced retinal degenerations, glaucoma, or optic atrophy.
“Consequently, a retinal prosthesis may not be useful, for example, in patients with advanced retinal degenerations, glaucoma, or optic atrophy.”
Quote in the paperSubstantial claim- Rests on an assumption: The inner layers of the retina can degenerate in many retinal diseases.
- Premisecitation
Large surface electrodes interacted with relatively large volumes of cortex (~1 cm3), resulting in very low spatial resolution of the perceived phosphenes.
“In addition, these large electrodes interacted with relatively large volumes of cortex (∼1 cm3), resulting in very low spatial resolution of the perceived phosphenes (Christie et al., 2016; Niketeghad et al., 2019).”
Quote in the paperSubstantial claim0 of 2 sources checked - Premisecitation
There are no treatments for all causes of blindness.
“unfortunately, there are not treatments for all causes of blindness (Fernandez, 2018).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Fernandez, 2018 source
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- Premisecitation
Inflammatory responses to the implantation of any neural probe into the brain involve a large network of physiological responses including edema, release of cytokines, platelet activation, complement system activation, invasion of blood-borne macrophages, and activation of neighboring astrocytes and microglial cells.
“the inflammatory responses to the implantation of any neural probe into the brain involve a large network of physiological responses including edema, release of cytokines, platelet activation, complement system activation, invasion of blood-borne macrophages, and activation of neighboring astrocytes and microglial cells”
Quote in the paperSubstantial claim0 of 3 sources checked- cites Zhong and Bellamkonda, 2008
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- cites Marin and Fernandez, 2010
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- cites Fernandez and Botella, 2017
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- Premisecitation
It is still unclear how to identify the ideal candidates for a cortical prosthesis.
“Moreover, it is still unclear how to identify the ideal candidates for a cortical prosthesis (Merabet et al., 2007).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Merabet et al., 2007 source
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- Premisecitation
Early findings by Foerster and Penfield established the anatomical and physiological basis for the development of a cortical visual prosthesis for the blind.
“These early findings, together with the studies of Wilder Penfield and co-workers in epileptic patients (Penfield and Rasmussen, 1950; Penfield and Jaspers, 1974), established the anatomical and physiological basis for the development of a cortical visual prosthesis for the blind.”
Quote in the paperNot a substantial claim0 of 3 sources checked- cites Foerster, 1929
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- cites Penfield and Rasmussen, 1950
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- cites Penfield and Jaspers, 1974
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- Interpretationcitation
Cortical artificial vision did not seem feasible until a way was found to provide much more focal stimulation of neurons in the visual cortex.
“Cortical artificial vision did not seem feasible until we could find a way to provide a much more focal stimulation of neurons in the visual cortex (Normann et al., 1996).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Normann et al., 1996 source
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- Premisecitation
When multiple surface electrodes were stimulated simultaneously in two blind individuals, phosphenes fused into larger formless perceptions, making shape recognition impossible.
“These later findings have recently been confirmed by Beauchamp et al. (2020), who implanted two different types of electrodes on the surface of the visual cortex of two blind individuals and found that when multiple electrodes were stimulated simultaneously, phosphenes fused into larger formless perceptions, making shape recognition impossible.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Beauchamp et al. (2020) source
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- Interpretationreasoning
The problems of surface stimulation were associated with the large active surface of the electrodes, which required high electrical currents of the order of milliamps to evoke phosphenes.
“These issues were associated with the large active surface of the electrodes, which required high electrical currents of the order of milliamps to evoke phosphenes.”
Quote in the paperSubstantial claim - Premisecitation
At present, retinal prostheses are the most successful approach in the field of visual prostheses.
“At present, retinal prostheses are the most successful approach in this field, and several retinal devices have already been approved for patients with retinal dystrophies (Da Cruz et al., 2016; Stingl et al., 2017).”
Quote in the paperSubstantial claim0 of 2 sources checked - Premisecitation
Electrical stimulation of the occipital area of one cerebral hemisphere in an awake patient induced the perception of small spots of light directly in front of the subject.
“He found that electrical stimulation of this region of the brain induced the perception of small spots of light directly in front of the subject.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Foerster, 1929
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- Premisecitation
Surface stimulation of the brain induced problems such as epileptic seizures and pain due to meningeal or scalp stimulation.
“However, there were also some problems, such as the induction of epileptic seizures and the appearance of pain due to meningeal or scalp stimulation.”
Quote in the paperSubstantial claim0 of 2 sources checked- cites Brindley and Lewin, 1968a, b
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- cites Dobelle and Mladejovsky, 1974 source
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- Interpretationcitation
All these factors place high demands on the long-term function of any intracortical electrode and impose unique constraints for the materials, packaging, and insulation of the electronics.
“All of these factors place high demands on the long-term function of any intracortical electrode and also impose unique constrains for the materials, packaging, and insulation of the electronics (Normann and Fernandez, 2016).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Normann and Fernandez, 2016 source
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- Rests on an assumption: The brain imposes specific conditions such as the absence of regeneration and the presence of different types of glial cells.
- Rests on an assumption: The requirements for electrical stimulation and recording in the brain are clearly different from those in the peripheral nervous system.
- Rests on an assumption: The brain hosts different types of neurons arranged in several superficial layers and in deep nuclei and various types of glial cells that interact in very intricate ways.
- Rests on an assumption: The brain is protected by the meninges, a multi-layered structure formed by connective tissue, bone, and skin.
- Interpretationreasoning
It is impossible to reach the desired cortical neurons without affecting neighboring parts of the nervous system.
“This means that it is impossible to reach the desired cortical neurons without affecting neighboring parts of the nervous system.”
Quote in the paperNot a substantial claim- Rests on an assumption: The brain is protected by the meninges, a multi-layered structure formed by connective tissue, bone, and skin.
- Interpretationreasoning
Even if only a crude representation of the surrounding physical world can be evoked, a blind individual could use this artificially encoded neural information for tasks such as orientation and mobility.
“Even if only a crude representation of the surrounding physical world can be evoked, a blind individual could use this artificially encoded neural information for tasks such as orientation and mobility.”
Quote in the paperSubstantial claim - Interpretationreasoning
The device must be wireless, since it is necessary to avoid wires to reduce post-surgical complications such as the risk of infection.
“Furthermore, the device must be wireless, since it is necessary to avoid wires to reduce post-surgical complications such as, for example, the risk of infection.”
Quote in the paperSubstantial claim - Premisecitation
Activated macrophages surround the microelectrodes and fuse into multi-nucleated giant cells that form a barrier that shields brain tissue from damage.
“Subsequently, activated macrophages surround the microelectrodes and fuse into multi-nucleated giant cells that form a barrier, similar to a thin protective membrane, that shields brain tissue from damage (Polikov et al., 2005).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Polikov et al., 2005 source
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- Premisecitation
Modification of the chemical composition of the surface of the electrodes by using different polymers and nanomaterials is a relatively simple way to control biological responses and improve long-term biotolerability of neural electrodes.
“Another relatively simple way to control the biological responses and improve the long-term biotolerability of neural electrodes is the modification of the chemical composition of the surface of the electrodes by using different polymers and nanomaterials (Hara et al., 2016; Fernandez and Botella, 2017; Gulino et al., 2019).”
Quote in the paperNot a substantial claim0 of 3 sources checked - Interpretationcitation
Providing some degree of functional vision to facilitate activities of daily living with only around 600-700 electrodes is possible.
“In this framework, the possibility of providing some degree of functional vision to facilitate the activities of daily living with only around 600–700 electrodes is very encouraging (Dagnelie et al., 2006).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Dagnelie et al., 2006 source
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- Premisecitation
Part of the success of cochlear implants seems to be related to the development of sophisticated signal-processing techniques and bioinspired coding strategies developed over the years.
“Part of the success of cochlear implants seems to be related to the development of sophisticated signal-processing techniques and bioinspired coding strategies developed over the years (Clark, 2015; Boulet et al., 2016; Jain and Vipin Ghosh, 2018).”
Quote in the paperNot a substantial claim0 of 3 sources checked - Premisecitation
Multiple microelectrode arrays have already been implanted in monkey visual cortex.
“multiple microelectrode arrays have already been implanted in monkey visual cortex (Chen et al., 2017; Roelfsema and Holtmaat, 2018; Van Vugt et al., 2018; Self et al., 2019)”
Quote in the paperNot a substantial claim0 of 3 sources checked - Premisecitation
Humans can extract complex information, such as identifying human faces, from relatively poor-quality images by using specific cues and multiple visual features.
“Thus, we can extract complex information, such as identifying human faces, from relatively poor-quality images by using specific cues and multiple visual features (Sinha, 2002).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Sinha, 2002 source
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- Premisenone given
There is clear clinical evidence showing adaptive neurophysiological changes in the brain, specifically at the occipital lobe.
“however, there is clear clinical evidence showing adaptive neurophysiological changes in the brain, specifically at the occipital lobe.”
Quote in the paperNot a substantial claim - Interpretationnone given
A low number of electrodes (around 600-700) usually implies a "tunnel vision": a restricted visual field that can be a serious problem for orientation and mobility.
“However, this low number of electrodes also usually implies a “tunnel vision”: a restricted visual field that can be a serious problem for orientation and mobility.”
Quote in the paperSubstantial claim - Premisecitation
These implants in monkey visual cortex are providing a better understanding of how the brain enhances the representations of visual objects in different visual regions.
“these implants are providing a better understanding of how the brain enhances the representations of visual objects in different visual regions (Klink et al., 2017; Self et al., 2019).”
Quote in the paperNot a substantial claim0 of 2 sources checked - Premisecitation
Reduction of the cross-sectional area of electrodes and use of more flexible and soft materials that better match surrounding tissue have been investigated as strategies for minimizing trauma and inflammatory responses.
“several strategies for minimizing trauma and the inflammatory responses have been investigated, for example, the reduction of the cross-sectional area of the electrodes (Seymour and Kipke, 2007) and the use of more flexible and soft materials that better match the properties of the surrounding tissue”
Quote in the paperNot a substantial claim0 of 3 sources checked - Premisecitation
The functional vision that could be restored with an array of intracortical microelectrodes implanted into the brain is in part related to the number of implanted electrodes, the interelectrode spacing, and the specific location of each microelectrode in the brain.
“The functional vision that could be restored with an array of intracortical microelectrodes implanted into the brain is a function of many parameters, but it is in part related to the number of implanted electrodes, the interelectrode spacing, and the specific location of each microelectrode in the brain (Cha et al., 1992; Dagnelie et al., 2006).”
Quote in the paperSubstantial claim0 of 2 sources checked - Premisenone given
Electrical stimulation via multiple electrodes may give rise to useful vision.
“Although ongoing studies suggest that electrical stimulation via multiple electrodes may give rise to useful vision, extensive efforts are still needed to address the engineering challenges of realizing an intracortical device containing hundreds of electrodes.”
Quote in the paperSubstantial claim - Premisecitation
In a series of psychophysical experiments, it has been estimated that 625 electrodes implanted at the primary visual cortex could be enough for reading (although to lower speeds) and to navigate through complex visual environments.
“In a series of psychophysical experiments, it has been estimated that 625 electrodes implanted at the primary visual cortex could be enough for reading (although to lower speeds) and to navigate through complex visual environments (Cha et al., 1992).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Cha et al., 1992 source
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- Interpretationreasoning
The assumption that visual perception will improve by increasing only the number of electrodes may be incorrect.
“However, the assumption that visual perception will improve by increasing only the number of electrodes may be incorrect.”
Quote in the paperSubstantial claim - Premisecitation
The adult visual cortex does not completely lose its functional capacity after years of deprivation of visual input.
“The adult visual cortex does not completely lose its functional capacity after years of deprivation of visual input (Brindley and Lewin, 1968a);”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Brindley and Lewin, 1968a
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- Premisecitation
Results of several simulation studies suggest that the amount of visual input required to perform basic visually guided tasks is not as great as one might expect.
“Fortunately, despite the above-mentioned figures, the results of several simulation studies suggest that the amount of visual input required to perform basic visually guided tasks is not as great as one might expect.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Cha et al., 1992 source
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- Interpretationreasoning
These changes are related to the capability of blind subjects to extract greater information from other senses such as touch and hearing.
“These changes are related to the capability of blind subjects to extract greater information from other senses such as touch and hearing.”
Quote in the paperNot a substantial claim - Premisecitation
In response to the loss of vision, brain areas normally devoted to the processing of visual information are recruited to process tactile and auditory information and even cognitive functions such as verbal memory and speech processing.
“In response to the loss of vision, brain areas normally devoted to the processing of visual information are recruited to process tactile and auditory information and even cognitive functions such as verbal memory and speech processing (Fernandez et al., 2005; Gilbert et al., 2009; Legge and Chung, 2016; Beyeler et al., 2017; Singh et al., 2018; Castaldi et al., 2020).”
Quote in the paperSubstantial claim0 of 3 sources checked - Interpretationreasoning
It is unlikely that the re-introduction of the lost sensory input alone will be able to promptly restore sight.
“On the other hand, it is unlikely that the re-introduction of the lost sensory input alone will be able to promptly restore sight.”
Quote in the paperSubstantial claim - Interpretationcitation
Neuroplasticity implies that the brain undergoes important remodeling and adaptive changes after the onset of blindness that could directly impact the success of any cortical prosthesis.
“This neuroplasticity implies that the brain undergoes important remodeling and adaptive changes after the onset of the blindness that could directly impact the success of any cortical prosthesis (Glennon et al., 2019).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Glennon et al., 2019 source
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- May combine two claims. 16
- Classified as probably not a substantial claim. 4
May combine two claims.
Premisenone givenImplantation of any intracortical microelectrode into the brain is a traumatic procedure, and all neural electrodes to date, even those considered highly biocompatible, induce biological responses characterized by small microhemorrhages and local tissue damage around the electrodes that may impact the stability, performance, and viability of the microelectrodes.
“The implantation of any intracortical microelectrode into the brain is a traumatic procedure, and all neural electrodes to date, even those considered to be highly biocompatible, induce biological responses characterized by small microhemorrhages and a certain amount of local tissue damage around the electrodes that may impact the stability, performance, and viability of the microelectrodes.”
Quote in the paperNot a substantial claimMay combine two claims.
PremisereasoningMicrohemorrhages stop spontaneously, but increased blood flow to the damaged region and increased permeability of local microvasculature induce extravasation of fluids, blood cells, and proteins toward the interstitial space.
“These microhemorrhages stop spontaneously, but there is also increased blood flow to the damaged region, together with increased permeability of local microvasculature, which induces extravasation of fluids, blood cells, and proteins toward the interstitial space.”
Quote in the paperSubstantial claimMay combine two claims.
PremisecitationAuditory prostheses have already allowed many deaf patients to hear sounds and acquire language capabilities.
“These devices have already allowed many deaf patients to hear sounds and acquire language capabilities (Merkus et al., 2014; Glennon et al., 2019), and the same hope exists in the field of neuroprosthetic devices designed for electrical stimulation of the visual cortex.”
Quote in the paperNot a substantial claim0 of 2 sources checkedMay combine two claims.
PremisereasoningNew microelectrodes can be located very close to the neurons they intend to stimulate, which are situated generally at 1-1.5 mm from the cortical surface, avoiding the relatively high electrical currents required by surface electrodes.
“These new microelectrodes can be located very close to the neurons they intend to stimulate, which are situated generally at 1–1.5 mm from the cortical surface, avoiding the relatively high electrical currents required by surface electrodes.”
Quote in the paperSubstantial claimMay combine two claims.
PremisecitationMost materials used currently for the fabrication of intracortical electrodes remain relatively inert in the brain, but they still induce a foreign-body reaction (FBR) characterized by a neuroinflammatory response of the tissue around the electrodes that may hinder the recording and stimulation of the neurons over time.
“While most materials used currently for the fabrication of intracortical electrodes remain relatively inert in the brain, they still induce a foreign-body reaction (FBR) characterized by a neuroinflammatory response of the tissue around the electrodes that may hinder the recording and stimulation of the neurons over time (Marin and Fernandez, 2010; Fernandez and Botella, 2017).”
Quote in the paperSubstantial claim0 of 2 sources checked- cites Marin and Fernandez, 2010
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- cites Fernandez and Botella, 2017
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Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).
Premisenone givenBrain tissue includes a complex network of blood vessels that are likely to be injured by the introduction of any external device.
“Likewise, the brain tissue includes a complex network of blood vessels that are likely to be injured by the introduction of any external device (Figure 1).”
Quote in the paperNot a substantial claimProbably not a substantial claim: may not pass S3 (load-bearing).
PremisecitationSeveral research groups are focusing on developing artificial vision approaches based on electric stimulation of the retina.
“several research groups are focusing their efforts on the development of new approaches for artificial vision based on electric stimulation of the retina”
Quote in the paperNot a substantial claim0 of 3 sources checkedMay combine two claims.
InterpretationreasoningIn order to encode all features of objects in the visual space and their change in time in the same way that the human retina does, at least 1 million parallel channels would be needed, which is well beyond the state-of-the-art of current prosthetic technologies.
“This means that, in order to encode all the features of objects in the visual space (for example, their form, localization, contour, intensity, color, etc.) and the change of these features in time in the same way that the human retina does, we would need at least 1 million parallel channels, which is clearly well beyond the state-of-the-art of current prosthetic technologies.”
Quote in the paperSubstantial claimMay combine two claims.
PremisecitationThe output neurons of the retina are ganglion cells, which send their axons (approximately 1-1.5 million per eye) through the optic nerve to the brain.
“The output neurons of the retina are the ganglion cells, which send their axons (approximately 1–1.5 million per eye) through the optic nerve to the brain (Watson, 2014).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Watson, 2014 source
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May combine two claims.
PremisecitationCrosstalk or interference between stimulating electrode sites and the multiplexing of stimulation channels are relevant issues.
“Other relevant issues in this framework are the so-called “crosstalk” or interference between stimulating electrode sites and the multiplexing of stimulation channels (Barriga-Rivera et al., 2017).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Barriga-Rivera et al., 2017 source
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May combine two claims.
Premisenone givenPatients with retinal implants have to undergo long fitting procedures to measure thresholds and fine-tune the stimulation parameters on each individual electrode, but these procedures are not viable if hundreds or thousands of electrode sites need to be tested.
“On the other hand, patients with retinal implants have to undergo long fitting procedures to measure thresholds and fine-tune the stimulation parameters on each individual electrode, but these procedures are not viable if hundreds or thousands of electrode sites need to be tested.”
Quote in the paperSubstantial claimMay combine two claims.
InterpretationreasoningA chronic inflammation reaction persists over time and can induce the development of a dense sheath around the microelectrodes, making it difficult to record and stimulate nearby neurons.
“This suggests the existence of a chronic inflammation reaction that persists over time and can induce the development of a dense sheath around the microelectrodes, making it difficult to record and stimulate nearby neurons.”
Quote in the paperSubstantial claimMay combine two claims.
InterpretationreasoningModifications to reduce cross-sectional area or use softer materials also affect the mechanical properties of the electrodes and could result in a lack of mechanical strength needed to withstand insertion without buckling and breaking.
“However, these modifications also affect the mechanical properties of the electrodes and could result in a lack of the mechanical strength needed to withstand insertion without buckling and breaking.”
Quote in the paperSubstantial claimProbably not a substantial claim: may not pass S4 (based).
Premisenone givenAll visual prostheses developed to date provide very poor vision, with relatively low spatial resolution.
“All visual prostheses developed to date provide very poor vision, with relatively low spatial resolution; therefore, great efforts are still needed to design and develop new systems that can have results similarly successful as those achieved with cochlear implants.”
Quote in the paperNot a substantial claimMay combine two claims.
PremisecitationElectronics and connecting pathways to individual microelectrodes must be completely insulated and remain perfectly functional over time, imposing unique constraints on hermetic packaging.
“Moreover, we should also consider that the electronics and the connecting pathways to individual microelectrodes must be completely insulated and have to remain perfectly functional over time, which also imposes unique constraints on hermetic packaging (Jiang and Zhou, 2009; Vanhoestenberghe and Donaldson, 2013).”
Quote in the paperSubstantial claim0 of 2 sources checked- cites Jiang and Zhou, 2009
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- cites Vanhoestenberghe and Donaldson, 2013
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May combine two claims.
PremisecitationPower and communication constraints, as well as power dissipation in the brain, could pose significant challenges.
“In this context, power and communication constraints, as well as power dissipation in the brain, could pose significant challenges (Sahin and Pikov, 2011; Lewis et al., 2015).”
Quote in the paperSubstantial claim0 of 2 sources checked- cites Sahin and Pikov, 2011
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- cites Lewis et al., 2015 source
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May combine two claims.
Premisenone givenMost visual prosthesis devices only try to emulate the phototransducer aspects of the retina and do not consider the complex processes that are found in the mammalian visual system.
“Despite these encouraging results, most visual prosthesis devices only try to emulate the phototransducer aspects of the retina and do not consider the complex processes that are found in the mammalian visual system.”
Quote in the paperNot a substantial claimMay combine two claims.
PremisecitationMost of these processes are spontaneously resolved; however, glial scarring and giant cells can be found around many microelectrodes implanted chronically in the brain.
“Most of these processes are spontaneously resolved; however, glial scarring and giant cells can be found around many microelectrodes implanted chronically in the brain (Polikov et al., 2005).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Polikov et al., 2005 source
Not checked in the free run.
Probably not a substantial claim: may not pass S4 (based). May combine two claims.
InterpretationreasoningOver time, these adaptive changes may lead to the establishment of new connections and functional roles of different brain areas, which is probably influenced by factors such as the cause of the visual loss and the duration of visual deprivation.
“Over time, these adaptive changes may lead to the establishment of new connections and functional roles of different brain areas, which is probably influenced by factors such as the cause of the visual loss and the duration of visual deprivation.”
Quote in the paperNot a substantial claim
The paper relies on this without support.
The inner layers of the retina can degenerate in many retinal diseases.
“However, the inner layers of the retina can degenerate in many retinal diseases.”
The paper relies on this without support.
Neurons in the higher visual regions of the brain are usually spared from the damage to the retina and optic nerve.
“since the neurons in the higher visual regions of the brain are usually spared from the damage to the retina and optic nerve”
The paper relies on this without support.
The brain imposes specific conditions such as the absence of regeneration and the presence of different types of glial cells.
“the brain imposes some specific conditions such as the absence of regeneration and the presence of different types of glial cells.”
The paper relies on this without support.
The requirements for electrical stimulation and recording in the brain are clearly different from those in the peripheral nervous system.
“Moreover, the requirements for electrical stimulation and recording in the brain are clearly different from those in the peripheral nervous system.”
The paper relies on this without support.
The brain hosts different types of neurons arranged in several superficial layers and in deep nuclei and various types of glial cells that interact in very intricate ways.
“Thus, the brain hosts different types of neurons arranged in several superficial layers and in deep nuclei and various types of glial cells that interact in very intricate ways.”
The paper relies on this without support.
The brain is protected by the meninges, a multi-layered structure formed by connective tissue, bone, and skin.
“Furthermore, the brain is protected by the meninges, a multi-layered structure formed by connective tissue, bone, and skin.”
The paper relies on this without support.
The human retina is approximately 0.5 mm thick and contains photoreceptors and intricate neural circuits that perform the first stages of imaging processing.
“The human retina is approximately 0.5 mm thick and contains both the photoreceptors or sensory neurons that respond to light and intricate neural circuits that perform the first stages of imaging processing.”
The paper relies on this without support.
Most current coding strategies for visual prostheses address only spatial details, despite many relevant aspects in a visual scene such as form, color, and motion.
“whereas there are many relevant aspects in a visual scene (for example, form, color, and motion), most current coding strategies are only aimed at addressing the spatial details.”
The paper relies on this without support.
The ability to recognize patterns in a scene, or the perceived receptive field size, is critical for many visual tasks.
“the ability to recognize patterns in a scene, or the perceived receptive field size, is critical for many visual tasks.”
The paper relies on this without support.
There may be subtle differences among subjects in the perceived visual field or in coding.
“In addition, it is possible that there are subtle differences in the perceived visual field or in coding among subjects.”
The paper relies on this without support.
Some people may place more demands on object- or person-identification, whereas others could prefer to focus on orientation and mobility.
“For example, some people may place more demands on object- or person-identification, whereas others could prefer to focus on orientation and mobility.”
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
There is no treatment for all causes of blindness.
“unfortunately, there is no treatment for all causes of blindness (Fernandez, 2018; Fernandez et al., 2020).”
From Toward a personalized closed-loop stimulation of the visual cortex: Advances and challenges (2022) · cites this paper as Fernandez et al., 2020
The biological and engineering problems for the success of cortical implants are much more complex than originally believed and involve long-term biocompatibility issues and challenges related to encoding of visual information and delivery of information to implants.
“However, the biological and engineering problems for the success of cortical implants are much more complex than originally believed and involve, for example, long-term biocompatibility issues and challenges related to the encoding of visual information and the delivery of information to implants (Fernandez et al., 2020).”
From Toward a personalized closed-loop stimulation of the visual cortex: Advances and challenges (2022) · cites this paper as Fernandez et al., 2020
The inflammatory response of brain tissue is a major concern that limits the long-term viability of cortical electrode implants.
“For instance, the inflammatory response of brain tissue is a major concern that limits the long-term viability of cortical electrode implants (Fernández, Alfaro, & González-López, 2020; Polikov, Trresco, & Reichert, 2005)”
From End-to-end optimization of prosthetic vision (2022) · cites this paper as Fernández, Alfaro, & González-López, 2020
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Two purportedly distinct references have the same publication identifiers
MinorThe references list the same authors, journal, volume, pages, and PubMed ID as two differently titled 1968 publications. A single PubMed ID cannot identify both distinct articles.
“11. Brindley G. S. Lewin W. S. (1968a). The sensations produced by electrical stimulation of the visual cortex. J. Physiol. 196 479– 493. 10.1113/jphysiol.1968.sp008519 4871047 PMC1351724”
“12. Brindley G. S. Lewin W. S. (1968b). Short and long-term stability of cortical electrical phosphenes. J. Physiol. 196 479– 493. 4871047 PMC1351724”
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- Authors
- Fernández, E., Alfaro, A., & González-López, P.
- Affiliations
- Universitat de Miguel Hernández d'Elx (ES)
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (ES)
- Corresponding author
- Fernández, Eduardo
- Venue
- Frontiers in Neuroscience
- Publisher
- Frontiers Media SA
- Published
- 2020-08-11
- Volume
- 14
- Pages
- 681-681
- ISSN
- 1662-453X (ISSN-L)
- PMC
- PMC7431631
- OpenAlex
- W3048737326
- Cited by
- 35
- References
- 89
- Citations by year
- 2026: 6 · 2025: 3 · 2024: 4 · 2023: 6 · 2022: 12 · 2021: 4
- FWCI
- 2.50
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- Locations
- Frontiers in Neuroscience (publishedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Funders
- Generalitat Valenciana (PROMETEO/2019/119)
- Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina
- Topics
- Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuroscience and Neural Engineering
- Life Sciences › Neuroscience › Cognitive Neuroscience › Tactile and Sensory Interactions
- Life Sciences › Neuroscience › Cognitive Neuroscience › EEG and Brain-Computer Interfaces
- Keywords
- intracortical stimulation, visual prosthesis, blindness, visual cortex, electrode number, brain-computer interface
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