The Skin as a Medium for Sensory Substitution

2014 ◽  
Vol 27 (5-6) ◽  
pp. 293-312 ◽  
Author(s):  
Charles Spence
Keyword(s):  
Cortical Plasticity ◽  
Low Vision ◽  
Skin Surface ◽  
General Purpose ◽  
Pattern Perception ◽  
Sensory Substitution ◽  
Sensory Loss ◽  
Tactile Information ◽  
Cognitive Limitations ◽  
Locomotion Pattern

The last 50 years or so has seen great optimism concerning the potential of sensory substitution and augmentation devices to enhance the lives of those with (or even those without) some form of sensory loss (in practice, this has typically meant those who are blind or suffering from low vision). One commonly discussed solution for those individuals who are blind has been to use one of a range of tactile–visual sensory substitution systems that represent objects captured by a camera as outline images on the skin surface in real-time (what Loomis, Klatzky and Giudice, 2012, term general-purpose sensory substitution devices). However, despite the fact that touch, like vision, initially codes information spatiotopically, I would like to argue that a number of fundamental perceptual, attentional, and cognitive limitations constraining the processing of tactile information mean that the skin surface is unlikely ever to provide such general-purpose sensory substitution capabilities. At present, there is little evidence to suggest that the extensive cortical plasticity that has been demonstrated in those who have lost (or never had) a sense can do much to overcome the limitations associated with trying to perceive high rates of spatiotemporally varying information presented via the skin surface (no matter whether that surface be the back, stomach, forehead, or tongue). Instead, the use of the skin will likely be restricted to various special-purpose devices that enable specific activities such as navigation, the control of locomotion, pattern perception, etc.

Sensory Substitution: Unfulfilled Promises and Fundamental Limitations

2018 ◽  
pp. 251-266
Author(s):  
Charles Spence
Keyword(s):  
Sensory Substitution ◽  
Sensory Loss ◽  
Loss Of Vision ◽  
Fundamental Limitations ◽  
Processing Information ◽  
Technological Limitations

Many of the most attention-grabbing claims concerning the uptake of sensory substitution devices in the last 50 years have, noticeably, not come to pass. I highlight a number of the fundamental limitations (some acknowledged, others not) that may have prevented the development and uptake of these devices amongst individuals suffering from sensory loss. First and foremost, it may simply be impossible to fully substitute for the loss of vision (the sense most substituted for) given the imbalance in neural cortical resources given to processing information in the various senses. Second, the inability to substitute for the hedonic attributes of a given modality constitutes an important, if currently under-acknowledged, problem. Most researchers tend to focus their efforts on the substitution of the sensory-discriminative (primarily spatial) aspects of stimulation instead. Third, I highlight the technological limitations associated with providing useful substitution devices for those who have lost their sense of taste or smell, senses which, theoretically, should be far easier to substitute for. Another factor that may have limited the uptake of these devices—aesthetic concerns about the appearance of users wearing them—is, I believe, likely to disappear, as a range of other augmented-perception technologies become more widely accepted.

scholarly journals A closed-loop hand prosthesis with simultaneous intraneural tactile and position feedback

2019 ◽  
Vol 4 (27) ◽  
pp. eaau8892 ◽  
Author(s):  
Edoardo D’Anna ◽  
Giacomo Valle ◽  
Alberto Mazzoni ◽  
Ivo Strauss ◽  
Francesco Iberite ◽  
...  
Keyword(s):  
Visual Cues ◽  
Tactile Feedback ◽  
Sensory Substitution ◽  
Tactile Information ◽  
Position Information ◽  
Implanted Electrodes ◽  
Myoelectric Prostheses ◽  
Position Feedback ◽  
The Rich ◽  
Improved Function

Current myoelectric prostheses allow transradial amputees to regain voluntary motor control of their artificial limb by exploiting residual muscle function in the forearm. However, the overreliance on visual cues resulting from a lack of sensory feedback is a common complaint. Recently, several groups have provided tactile feedback in upper limb amputees using implanted electrodes, surface nerve stimulation, or sensory substitution. These approaches have led to improved function and prosthesis embodiment. Nevertheless, the provided information remains limited to a subset of the rich sensory cues available to healthy individuals. More specifically, proprioception, the sense of limb position and movement, is predominantly absent from current systems. Here, we show that sensory substitution based on intraneural stimulation can deliver position feedback in real time and in conjunction with somatotopic tactile feedback. This approach allowed two transradial amputees to regain high and close-to-natural remapped proprioceptive acuity, with a median joint angle reproduction precision of 9.1° and a median threshold to detection of passive movements of 9.5°, which was comparable with results obtained in healthy participants. The simultaneous delivery of position information and somatotopic tactile feedback allowed both amputees to discriminate the size and compliance of four objects with high levels of performance (75.5%). These results demonstrate that tactile information delivered via somatotopic neural stimulation and position information delivered via sensory substitution can be exploited simultaneously and efficiently by transradial amputees. This study paves a way to more sophisticated bidirectional bionic limbs conveying richer, multimodal sensations.

scholarly journals Human first-order tactile neurons can resolve spatial details on the scale of single fingerprint ridges

2020 ◽  
Author(s):  
Ewa Jarocka ◽  
J Andrew Pruszynski ◽  
Roland S Johansson
Keyword(s):  
Receptive Fields ◽  
Scanning Speed ◽  
Skin Surface ◽  
Spatial Period ◽  
Tactile Information ◽  
Spatial Selectivity ◽  
First Order ◽  
Highly Sensitive ◽  
Receptor Organ

AbstractFast-adapting type 1 (FA-1) and slow-adapting type 1 (SA-1) first-order tactile neurons provide detailed spatiotemporal tactile information when we touch objects with fingertips. The distal axon of these neuron types branches in the skin and innervates many receptor organs associated with fingerprint ridges (Meissner corpuscles and Merkel cell neurite complexes, respectively), resulting in heterogeneous receptive fields that include many highly sensitive zones or ‘subfields’. Using raised dots that tangentially scanned a neuron’s receptive field, here we examined the spatial resolution capacity of FA-1 and SA-1 neurons afforded by their heterogeneous receptive fields and its constancy across scanning speed and direction. We report that the resolution of both neuron types on average corresponds to a spatial period of ∼0.4 mm and provide evidence that a subfield’s spatial selectivity arises because its associated receptor organ measures mechanical events limited to a single fingerprint ridge. Accordingly, the sensitivity topography of a neuron’s receptive fields is quite stable over repeated mappings and over scanning speeds representative of real-world hand use. The sensitivity topography is substantially conserved also for different scanning directions, but the subfields can be relatively displaced by direction-dependent shear deformations of the skin surface.Significance StatementThe branching of the distal axon of first-order tactile neurons with receptor-organs associated with fingerprint ridges (Meissner and Merkel end-organs) results in cutaneous receptive fields composed of several distinct subfields spread across multiple ridges. We show that the spatial selectivity of the subfields typically corresponds to the dimension of the ridges (∼0.4 mm) and that neurons’ subfield layout is well preserved across tangential movement speeds and directions representative of natural use of the fingertips. We submit that the receptor-organ underlying a subfield essentially measures mechanical events at an individual ridge. That neurons receive convergent input from multiple subfields does not preclude the possibility that spatial details can be resolved on the scale of single fingerprint ridges by a population code.

scholarly journals Rewired Animals and Sensory Substitution: The Cause Is Not Cortical Plasticity

2018 ◽  
pp. 167-173
Author(s):  
J. Kevin O’regan
Keyword(s):  
Tool Use ◽  
Quality Of Experience ◽  
Cortical Plasticity ◽  
The Body ◽  
Sensory Substitution ◽  
Rubber Hand Illusion ◽  
Rubber Hand ◽  
Cortical Areas ◽  
Modes Of Interaction

Cortical plasticity is often invoked to explain changes in the quality or location of experience observed in rewired animals, in sensory substitution, in extension of the body through tool use, and in the rubber hand illusion. However this appeal to cortical plasticity may be misleading, because it suggests that the cortical areas that are plastic are themselves the loci of generation of experience. This would be an error, I claim, since cortical areas do not generate experience. Cortical areas participate in enabling the interaction of an agent with its environment, and the quality of this interaction constitutes the quality of experience. Thus it is not plasticity in itself, but the change in modes of interaction which plasticity allows, which gives rise to the change of experience observed in these studies.

Characteristics of Physical Training of Persons with Visual Impairment - From Instruction and Workout to Training and Competition

2018 ◽  
Vol 5 (1) ◽  
pp. 67-83
Author(s):  
Marko Aleksandrović
Keyword(s):  
Visual Impairment ◽  
Motor Development ◽  
Visual Information ◽  
Brain Injuries ◽  
Early Stage ◽  
Low Vision ◽  
Functional Health ◽  
Verbal Description ◽  
Tactile Information ◽  
Stage Of Development

SummaryVisual impairment as a congenital condition or acquired state is due to: eye diseases, physical injuries, falls, brain injuries, infections, etc. In relation to the degree of visual impairment, there are blind and low vision persons.Due to insufficient or non-existent visual information at an early stage of development, children with visual impairment are not aware of their own body and space, therefore they have problems with their own motion. The motor development of children with visual impairment is slow, which manifests through delayed walking, inaptitude, clumsiness, frequent fall and bad coordination. On the other hand, it is possible that the ultimate level of motor abilities of people with visual impairment can be approximate or the same as people without visual impairment.For an appropriate approach to physical exercise it is necessary to consider the following in a person with visual impairment: the amount and type of vision, physical, functional, health and mental state. The basic characteristics of implementing physical exercises with this population include: adaptation of teaching methods, adaptation of the exercise space and selection of appropriate requisites and equipment.The way of acquiring knowledge of the low vision children is visual information (regardless of the poor quality of their reception), and for blind children there are audible and tactile information. A constant, detailed verbal description of motions and movements is necessary in order to explain incomplete visual information and associate it with successive tactile information. An individual-led activity ensures understanding of the person with VI on the required movement. The analytical method is the dominant method during instructions and training.Sports in which people with visual impairment can participate are: athletics, chess, judo, ninepin bowling, tenpin bowling, shooting, swimming, torball, football 5, golf, showdown, golf, powerlifting, skiing, riding ... IBSA (International Blind Sport Federation) is an international sports organization that takes care of sports of persons with VI and is a member of the IPC (International Paralympic Committee). Competitions involving people with VI include: Paralympic Games, IBSA Games, world, continental, regional and national championships, as well as many international and national tournaments.

scholarly journals The Current Status of Somatostatin-Interneurons in Inhibitory Control of Brain Function and Plasticity

2016 ◽  
Vol 2016 ◽  
pp. 1-20 ◽  
Author(s):  
Isabelle Scheyltjens ◽  
Lutgarde Arckens
Keyword(s):  
Cortical Plasticity ◽  
Brain Plasticity ◽  
Ocular Dominance ◽  
Sensory Information ◽  
Sensory Function ◽  
Sensory Loss ◽  
Current Status ◽  
Normal Brain ◽  
Ocular Dominance Plasticity ◽  
Dependent Plasticity

The mammalian neocortex contains many distinct inhibitory neuronal populations to balance excitatory neurotransmission. A correct excitation/inhibition equilibrium is crucial for normal brain development, functioning, and controlling lifelong cortical plasticity. Knowledge about how the inhibitory network contributes to brain plasticity however remains incomplete. Somatostatin- (SST-) interneurons constitute a large neocortical subpopulation of interneurons, next to parvalbumin- (PV-) and vasoactive intestinal peptide- (VIP-) interneurons. Unlike the extensively studied PV-interneurons, acknowledged as key components in guiding ocular dominance plasticity, the contribution of SST-interneurons is less understood. Nevertheless, SST-interneurons are ideally situated within cortical networks to integrate unimodal or cross-modal sensory information processing and therefore likely to be important mediators of experience-dependent plasticity. The lack of knowledge on SST-interneurons partially relates to the wide variety of distinct subpopulations present in the sensory neocortex. This review informs on those SST-subpopulations hitherto described based on anatomical, molecular, or electrophysiological characteristics and whose functional roles can be attributed based on specific cortical wiring patterns. A possible role for these subpopulations in experience-dependent plasticity will be discussed, emphasizing on learning-induced plasticity and on unimodal and cross-modal plasticity upon sensory loss. This knowledge will ultimately contribute to guide brain plasticity into well-defined directions to restore sensory function and promote lifelong learning.

Sensory deprivation after focal ischemia in mice accelerates brain remapping and improves functional recovery through Arc-dependent synaptic plasticity

2018 ◽  
Vol 10 (426) ◽  
pp. eaag1328 ◽  
Author(s):  
Andrew W. Kraft ◽  
Adam Q. Bauer ◽  
Joseph P. Culver ◽  
Jin-Moo Lee
Keyword(s):  
Ischemic Stroke ◽  
Synaptic Plasticity ◽  
Molecular Mechanisms ◽  
Barrel Cortex ◽  
Cortical Plasticity ◽  
Sensory Deprivation ◽  
Sensory Loss ◽  
Behavioral Recovery ◽  
Functional Reorganization ◽  
Sensorimotor Recovery

Recovery after stroke, a major cause of adult disability, is often unpredictable and incomplete. Behavioral recovery is associated with functional reorganization (remapping) in perilesional regions, suggesting that promoting this process might be an effective strategy to enhance recovery. However, the molecular mechanisms underlying remapping after brain injury and the consequences of its modulation are poorly understood. Focal sensory loss or deprivation has been shown to induce remapping in the corresponding brain areas through activity-regulated cytoskeleton-associated protein (Arc)–mediated synaptic plasticity. We show that targeted sensory deprivation via whisker trimming in mice after induction of ischemic stroke in the somatosensory cortex representing forepaw accelerates remapping into the whisker barrel cortex and improves sensorimotor recovery. These improvements persisted even after focal sensory deprivation ended (whiskers allowed to regrow). Mice deficient in Arc, a gene critical for activity-dependent synaptic plasticity, failed to remap or recover sensorimotor function. These results indicate that post-stroke remapping occurs through Arc-mediated synaptic plasticity and is required for behavioral recovery. Furthermore, our findings suggest that enhancing perilesional cortical plasticity via focal sensory deprivation improves recovery after ischemic stroke in mice.

scholarly journals Learning to Integrate an Artificial Sensory Device: From Decision Fusion to Sensory Integration

2020 ◽  
Author(s):  
Mohammad-Ali Nikouei Mahani ◽  
Karin Maria Bausenhart ◽  
Rolf Ulrich ◽  
Majid Nili Ahmadabadi
Keyword(s):  
Formal Analysis ◽  
Sensory System ◽  
Sensory Information ◽  
Discrimination Performance ◽  
Decision Fusion ◽  
Sensory Substitution ◽  
Visual Direction ◽  
High Signal ◽  
Integration Policy ◽  
Tactile Information

AbstractThe present study examines how artificial tactile stimulation from a novel non-invasive sensory device is learned and integrated with information from another sensory system. Participants were trained to identify the direction of visual dot motion stimuli with a low, medium, and high signal-to-noise ratio. In bimodal trials, this visual direction information was paired with reliable symbolic tactile information. Over several blocks of training, discrimination performance in unimodal tactile test trials improved, indicating that participants were able to associate the visual and tactile information and thus learned the meaning of the symbolic tactile cues. Formal analysis of the results in bimodal trials showed that the information from both modalities was integrated according to two different integration policies. Initially, participants seemed to rely on a linear decision integration policy based on the metacognitive experience of confidence. In later learning phases, however, our results are consistent with a Bayesian integration policy, that is, optimal integration of sensory information. Thus, the present study demonstrates that humans are capable of learning and integrating an artificial sensory device delivering symbolic tactile information. This finding connects the field of multisensory integration research to the development of sensory substitution systems.

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