Performance of blind and sighted humans on a tactile grating detection task

Biometric-Tuned E-Skin Sensor with Real Fingerprints Provides Insights on Tactile Perception: Rosa Parks Had Better Surface Vibrational Sensation than Richard Nixon

The dense mechanoreceptors in human fingertips enable texture discrimination. Recent advances in flexible electronics have created tactile sensors that effectively replicate slowly adapting (SA) and rapidly adapting (RA) mechanoreceptors. However, the influence of dermatoglyphic structures on tactile signal transmission, such as the effect of fingerprint ridge filtering on friction-induced vibration frequencies, remains unexplored. A novel multi-layer flexible sensor with an artificially synthesized skin surface capable of replicating arbitrary fingerprints is developed. This sensor simultaneously detects pressure (SA response) and vibration (RA response), enabling texture recognition. Fingerprint ridge patterns from notable historical figures - Rosa Parks, Richard Nixon, Martin Luther King Jr., and Ronald Reagan - are fabricated on the sensor surface. Vibration frequency responses to assorted fabric textures are measured and compared between fingerprint replicas. Results demonstrate that fingerprint topography substantially impacts skin-surface vibrational transmission. Specifically, Parks' fingerprint structure conveyed higher frequencies more clearly than those of Nixon, King, or Reagan. This work suggests individual fingerprint ridge morphological variation influences tactile perception and can confer adaptive advantages for fine texture discrimination. The flexible bioinspired sensor provides new insights into human vibrotactile processing by modeling fingerprint-filtered mechanical signals at the finger-object interface.

Blind individuals' enhanced ability to sense their own heartbeat is related to the thickness of their occipital cortex

Blindness is associated with heightened sensory abilities, such as improved hearing and tactile acuity. Moreover, recent evidence suggests that blind individuals are better than sighted individuals at perceiving their own heartbeat, suggesting enhanced interoceptive accuracy. Structural changes in the occipital cortex have been hypothesized as the basis of these behavioral enhancements. Indeed, several studies have shown that congenitally blind individuals have increased cortical thickness within occipital areas compared to sighted individuals, but how these structural differences relate to behavioral enhancements is unclear. This study investigated the relationship between cardiac interoceptive accuracy and cortical thickness in 23 congenitally blind individuals and 23 matched sighted controls. Our results show a significant positive correlation between performance in a heartbeat counting task and cortical thickness only in the blind group, indicating a connection between structural changes in occipital areas and blind individuals' enhanced ability to perceive heartbeats.

Biomechanical Considerations of Refreshable Braille and Tactile Graphics Toward Equitable Access: A Review

This review highlights the biomechanical foundations of braille and tactile graphic discrimination within the context of design innovations in information access for the blind and low-vision community. Braille discrimination is a complex and poorly understood process that necessitates the coordination of motor control, mechanotransduction, and cognitive-linguistic processing. Despite substantial technological advances and multiple design attempts over the last fifty years, a low-cost, high-fidelity refreshable braille and tactile graphics display has yet to be delivered. Consequently, the blind and low-vision communities are left with limited options for information access. This is amplified by the rapid adoption of graphical user interfaces for human-computer interaction, a move that the blind and low vision community were effectively excluded from. Text-to-speech screen readers lack the ability to convey the nuances necessary for science, technology, engineering, arts, and math education and offer limited privacy for the user. Printed braille and tactile graphics are effective modalities but are time and resource-intensive, difficult to access, and lack real-time rendering. Single- and multiline refreshable braille devices either lack functionality or are extremely cost-prohibitive. Early computational models of mechanotransduction through complex digital skin tissue and the kinematics of the braille reading finger are explored as insight into device design specifications. A use-centered, convergence approach for future designs is discussed in which the design space is defined by both the end-user requirements and the available technology.

Helping Blind People Grasp: Evaluating a Tactile Bracelet for Remotely Guiding Grasping Movements

The problem of supporting visually impaired and blind people in meaningful interactions with objects is often neglected. To address this issue, we adapted a tactile belt for enhanced spatial navigation into a bracelet worn on the wrist that allows visually impaired people to grasp target objects. Participants' performance in locating and grasping target items when guided using the bracelet, which provides direction commands via vibrotactile signals, was compared to their performance when receiving auditory instructions. While participants were faster with the auditory commands, they also performed well with the bracelet, encouraging future development of this system and similar systems.

Are blind individuals immune to bodily illusions? Somatic rubber hand illusion in the blind revisited

Multisensory awareness of one's own body relies on the integration of signals from various sensory modalities such as vision, touch, and proprioception. But how do blind individuals perceive their bodies without visual cues, and does the brain of a blind person integrate bodily senses differently from a sighted person? To address this question, we aimed to replicate the only two previous studies on this topic, which claimed that blind individuals do not experience the somatic rubber hand illusion, a bodily illusion triggered by the integration of correlated tactile and proprioceptive signals from the two hands. We used a larger sample size than the previous studies and added Bayesian analyses to examine statistical evidence in favor of the lack of an illusion effect. Moreover, we employed tests to investigate whether enhanced tactile acuity and cardiac interoceptive accuracy in blind individuals could also explain the weaker illusion. We tested 36 blind individuals and 36 age- and sex-matched sighted volunteers. The results show that blind individuals do not experience the somatic rubber hand illusion based on questionnaire ratings and behavioral measures that assessed changes in hand position sense toward the location of the rubber hand. This conclusion is supported by Bayesian evidence in favor of the null hypothesis. The findings confirm that blind individuals do not experience the somatic rubber hand illusion, indicating that lack of visual experience leads to permanent changes in multisensory bodily perception. In summary, our study suggests that changes in multisensory integration of tactile and proprioceptive signals may explain why blind individuals are "immune" to the nonvisual version of the rubber hand illusion.

Late Blindness and Deafness are Associated with Decreased Tactile Sensitivity, But Early Blindness is Not

Perceptual experience is shaped by a complex interaction between our sensory systems in which each sense conveys information on specific properties of our surroundings. This multisensory processing of complementary information improves the accuracy of our perceptual judgments and leads to more precise and faster reactions. Sensory impairment or loss in one modality leads to information deficiency that can impact other senses in various ways. For early auditory or visual loss, impairment and/or compensatory increase of the sensitivity of other senses are equally well described. Investigating individuals with deafness (N = 73), early (N = 51), late blindness (N = 49) and corresponding controls, we compared tactile sensitivity using the standard monofilament test on two locations, the finger and handback. Results indicate lower tactile sensitivity in people with deafness and late blindness but not in people with early blindness compared to respective controls, irrespective of stimulation location, gender, and age. Results indicate that neither sensory compensation nor simple use-dependency or a hindered development of the tactile sensory system is sufficient to explain changes in somatosensation after the sensory loss but that a complex interaction of effects is present.

Role of compounding awareness in vocabulary knowledge among Chinese children with blindness and sightedness

This study aimed to examine the role of compounding awareness in vocabulary knowledge acquisition among Chinese children with blindness compared to sighted children during the early (grades 1-3) and late (grades 4-6) primary school years, through a sample of 142 children with blindness. Regression analysis was used to explore the distinctive role of compounding awareness in vocabulary knowledge among children with blindness. First, the children's age, working memory, and rapid automatized naming were entered. Phonological awareness was entered in the second step, and compounding awareness was entered in the third and final steps. The results of regression analysis indicated that compounding awareness was a unique predictor of vocabulary knowledge among both children with blindness and sightedness during the early and late primary education levels. Moreover, the results showed that compounding awareness predicted more variation at the early primary level, especially among children with blindness. In particular, the results of this study highlight the essential and unique role of compounding awareness in the acquisition of vocabulary at the primary level among both children with blindness and sightedness.

The perception of affective and discriminative touch in blind individuals

Enhanced tactile acuity in blindness is among the most widely reported results of neuroplasticity following prolonged visual deprivation. However, tactile submodalities other than discriminative touch are profoundly understudied in blind individuals. Here, we examined the influence of blindness on two tactile submodalities, affective and discriminative touch, the former being vital for social functioning and emotional processing. We tested 36 blind individuals and 36 age- and sex-matched sighted volunteers. In Experiment 1, we measured the perception of affective tactile signals by asking participants to rate the pleasantness of touch delivered on the palm (nonhairy skin, sparsely innervated with C tactile [CT] fibers) or the forearm (hairy skin, densely innervated with CT fibers) in a CT-optimal versus a CT-nonoptimal manner using a paradigm grounded in studies on tactile sensory neurophysiology. In Experiment 2, we implemented a classic task assessing discriminative touch abilities, the grating orientation task. We found that blind individuals rated the touch as more pleasant when delivered on the palm than on the forearm, while the opposite pattern was observed for sighted participants, who rated stimulation on the forearm as more pleasant than stimulation on the palm. We also replicated the previous findings showing enhanced discriminative tactile acuity in blind individuals. Altogether, our results suggest that blind individuals might experience affective touch differently than sighted individuals, with relatively greater pleasantness perceived on the palm. These results provide a broader insight into somatosensory perception in blind individuals, for the first time taking into consideration the socioemotional aspect of touch.

Cross-Modal Plasticity in Brains Deprived of Visual Input Before Vision

Unimodal sensory loss leads to structural and functional changes in both deprived and nondeprived brain circuits. This process is broadly known as cross-modal plasticity. The evidence available indicates that cross-modal changes underlie the enhanced performances of the spared sensory modalities in deprived subjects. Sensory experience is a fundamental driver of cross-modal plasticity, yet there is evidence from early-visually deprived models supporting an additional role for experience-independent factors. These experience-independent factors are expected to act early in development and constrain neuronal plasticity at later stages. Here we review the cross-modal adaptations elicited by congenital or induced visual deprivation prior to vision. In most of these studies, cross-modal adaptations have been addressed at the structural and functional levels. Here, we also appraise recent data regarding behavioral performance in early-visually deprived models. However, further research is needed to explore how circuit reorganization affects their function and what brings about enhanced behavioral performance.

Analysing the Influence of Selected Eye Dysfunctions on Palpation Abilities of Massage Therapists

Introduction: Palpation arises controversy in the field of physiotherapy. On the one hand, this method provides a lot of valuable information. On the other, issues related to its reliability still exist. Additionally, questions about factors affecting palpation and users’ dispositions should be taken into consideration. Research objectives: The main aim of the study was to determine the impact of visual impairment on the palpatory skills of massage therapists. Material and methods: The research involved 58 participants divided into 3 groups. The first group consisted of 23, visually-impaired massage therapists, the second one was made up of 22 massage therapists and the control group consisted of 13 people unrelated to massage. The subjects took the hair test, the weight test and the measurement of Static Two-Point Discrimination within the fingertips I-III, thenar and hypothenar. Results: The analysis does not show any significant differences between the first and second group. Statistics reveal differences between the group of massage practitioners (group 1 and 2) and the control group. Visual impairment was not the most influential factor in the study. Conclusions: The level of palpation skills may be modified in both visually-impaired and healthy people. However, mechanisms that allow these modifications remain unclear. On the basis of the research, visual impairment is not considered as the only factor affecting palpation skills. Experience in palpation may well be an equally important factor.

Limits of Cross-modal Plasticity? Short-term Visual Deprivation Does Not Enhance Cardiac Interoception, Thermosensation, or Tactile Spatial Acuity

In the present study, we investigated the effect of short-term visual deprivation on discriminative touch, cardiac interoception, and thermosensation by asking 64 healthy volunteers to perform four behavioral tasks. The experimental group contained 32 subjects who were blindfolded and kept in complete darkness for 110minutes, while the control group consisted of 32 volunteers who were not blindfolded but were otherwise kept under identical experimental conditions. Both groups performed the required tasks three times: before and directly after deprivation (or control) and after an additional washout period of 40minutes, in which all participants were exposed to normal light conditions. Our results showed that short-term visual deprivation had no effect on any of the senses tested. This finding suggests that short-term visual deprivation does not modulate basic bodily senses and extends this principle beyond tactile processing to the interoceptive modalities of cardiac and thermal sensations.

Blindness and the Reliability of Downwards Sensors to Avoid Obstacles: A Study with the EyeCane

Vision loss has dramatic repercussions on the quality of life of affected people, particularly with respect to their orientation and mobility. Many devices are available to help blind people to navigate in their environment. The EyeCane is a recently developed electronic travel aid (ETA) that is inexpensive and easy to use, allowing for the detection of obstacles lying ahead within a 2 m range. The goal of this study was to investigate the potential of the EyeCane as a primary aid for spatial navigation. Three groups of participants were recruited: early blind, late blind, and sighted. They were first trained with the EyeCane and then tested in a life-size obstacle course with four obstacles types: cube, door, post, and step. Subjects were requested to cross the corridor while detecting, identifying, and avoiding the obstacles. Each participant had to perform 12 runs with 12 different obstacles configurations. All participants were able to learn quickly to use the EyeCane and successfully complete all trials. Amongst the various obstacles, the step appeared to prove the hardest to detect and resulted in more collisions. Although the EyeCane was effective for detecting obstacles lying ahead, its downward sensor did not reliably detect those on the ground, rendering downward obstacles more hazardous for navigation.

Detection of Simulated Tactile Gratings by Electro-Static Friction Show a Dependency on Bar Width for Blind and Sighted Observers, and Preliminary Neural Correlates in Sighted Observers

The three-dimensional micro-structure of physical surfaces produces frictional forces that provide sensory cues about properties of felt surfaces such as roughness. This tactile information activates somatosensory cortices, and frontal and temporal brain regions. Recent advances in haptic-feedback technologies allow the simulation of surface micro-structures via electro-static friction to produce touch sensations on otherwise flat screens. These sensations may benefit those with visual impairment or blindness. The primary aim of the current study was to test blind and sighted participants' perceptual sensitivity to simulated tactile gratings. A secondary aim was to explore which brain regions were involved in simulated touch to further understand the somatosensory brain network for touch. We used a haptic-feedback touchscreen which simulated tactile gratings using digitally manipulated electro-static friction. In Experiment 1, we compared blind and sighted participants' ability to detect the gratings by touch alone as a function of their spatial frequency (bar width) and intensity. Both blind and sighted participants showed high sensitivity to detect simulated tactile gratings, and their tactile sensitivity functions showed both linear and quadratic dependency on spatial frequency. In Experiment 2, using functional magnetic resonance imaging, we conducted a preliminary investigation to explore whether brain activation to physical vibrations correlated with blindfolded (but sighted) participants' performance with simulated tactile gratings outside the scanner. At the neural level, blindfolded (but sighted) participants' detection performance correlated with brain activation in bi-lateral supplementary motor cortex, left frontal cortex and right occipital cortex. Taken together with previous studies, these results suggest that there are similar perceptual and neural mechanisms for real and simulated touch sensations.

The association between tactile, motor and cognitive capacities and braille reading performance: a scoping review of primary evidence to advance research on braille and aging

PURPOSE

As the prevalence of age-related visual impairment increases, a greater understanding of the physiological and cognitive capacities that are recruited during braille reading and the potential implications of age-related declines is required.

METHODS

This scoping review aimed to identify and describe primary studies exploring the relationship between tactile, motor and cognitive capacities and braille reading performance, the instruments used to measure these capacities, and the extent to which age is considered within these investigations. English peer-reviewed articles exploring the relationship between these capacities and braille reading performance were included. Articles were screened by two researchers, and 91% agreement was achieved (kappa = 0.84 [0.81, 0.87], p < 0.01).

RESULTS

2405 articles were considered of which 36 met the inclusion criteria. Fifteen investigated the relationship between tactile capacities and braille reading performance, 25 explored motor capacities, and 5 considered cognitive capacities. Nineteen instruments were used to measure tactile capacity, 4 for motor dexterity, and 7 for cognitive capacity. These studies focus on younger participants and on those who learned braille early in life.

CONCLUSIONS

Although this overview underscores the importance of tactile perception and bimanual reading, future research is needed to explore the unique needs of older adults who learn braille later in life.IMPLICATIONS FOR REHABILITATIONThe studies in this review underscore the importance of developing both haptic tactile perception and efficient hand reading patterns early in the braille learning process.Practitioners should consider whether specific pre-braille readiness activities can be used to address the unique needs of older adults who may experience tactile, motor or cognitive declines.Most of the studies in this review require replication before they should serve as reliable clinical guidelines; however, braille reading (like print) is a complex process that draws on multiple capacities that should be developed in unison.The studies in this review focus heavily on younger participants and on those who learned braille early in life, and highlight the need for future research on braille and aging.

Enablers and barriers encountered by working-age and older adults with vision impairment who pursue braille training

PURPOSE

We explored the experiences of working-age and older adults with acquired vision impairment who pursued braille rehabilitation training, and the facilitators and barriers they encountered throughout this process.

METHODS

Semi-structured interviews of up to 90 min in length were conducted with 14 participants from across Canada who learned braille between the ages of 33 and 67 (Mdn = 46). Transcripts were analyzed by two researchers using interpretive phenomenological analysis.

RESULTS

A variety of personal, social and institutional factors characterize the adult braille learning experience. Among these, participants highlight the role of prior identity and experience, the impact of access to resources and the cost of materials and devices needed to maintain braille skills. Findings also emphasize invisible barriers, including the role of societal perceptions towards braille, the level of support provided by family and friends, and the influence of unconscious biases towards braille and aging held by both adult learners and those around them.

CONCLUSIONS

These findings provide important context to improve policies and practice in adult braille rehabilitation. As the prevalence of age-related vision impairment continues to increase, it will become imperative to understand the unique needs of working-age and older adults with acquired vision impairment who pursue braille.Implications for REHABILITATIONThis study is one of the first to explore the experiences of working-age and older adults with acquired visual impairment who pursue braille rehabilitation training.Rehabilitation professionals must take into account prior learning and reading experiences which may shape the braille learning process.Family members require greater access to resources and support during the training process.There is a significant need for public education to address societal misconceptions about braille and blindness that can lead to a reluctance to use braille.Interactions with other braille users foster more empowering definitions of braille that align with the social model understanding of disability.

Effects of environmental explanation using three-dimensional tactile maps for orientation and mobility training

We developed a new kit to assemble three-dimensional (3D) tactile maps for orientation and mobility (O&M) training provided to persons with visual impairments. This study evaluated the effects of verbal explanations combined with 3D tactile map kits in improving understanding, recall, and walking along an unfamiliar route in comparison with the effects of only verbal explanation. The 3D tactile maps provided participants having severe visual impairments and little experience with tactile maps with a better understanding and recall of the environmental information concerning the route and landmarks. Participants who used the 3D tactile maps could find specific landmarks set as tasks more accurately and arrive at the destination alone getting lost less frequently. Tactile maps composed of 3D points, lines, and areal parts are useful as a support aid for O&M training because they have high tactile readability and can provide the environmental information that individuals with visual impairment require.

The Stiffness Comparison Test: A pilot study to determine inter-individual differences in palpatory skill related to gender, age, and occupation-related experience

BACKGROUND

Manual palpation is a core skill in physical examination. Assessing elastic properties such as tissue stiffness has the potential for being an important diagnostics tool in the detection of cancer and other diseases.

OBJECTIVE

The study describes the newly developed Stiffness Comparison Test (SCT). The aim of our study was to test the SCT as a tool to detect interindividual differences in palpation skill related to gender, age and occupational experience.

METHODS

We used eight pairs of polyuterhane gel pads with the stiffness difference decreasing from the first to the last pair. Test subjects were asked to palpate each pair and determine stiffness differences.

PARTICIPANTS

We recruited 25 osteopaths, 48 other manual therapists and 50 participants from other non-manual professions.

RESULTS

As hypothesized there was no significant difference in SCT performance between the sexes (t(121) = 0.288, p = .774). To investigate if an age-related decline would have an effect on palpation skill, we carried out a linear regression. As hypothesized, the model did not predict any significant associations (F(1, 121) = 2.733, b = -0.149, p = .101, R² = 0.022). To compare the effect of occupational groups on SCT performance a one-way ANOVA was conducted. There were no statistically significant differences between group means (F(2, 120) = 0.598, p = .552).

CONCLUSIONS

The SCT can be used as simple and affordable tool for assessment, teaching and training in all disciplines of manual medicine. Further refinements of the tool are suggested to advance its discrimination power.

The effectiveness of an interactive audio-tactile map for the process of cognitive mapping and recall among people with visual impairments

BACKGROUND

People with visual impairments can experience numerous challenges navigating unfamiliar environments. Systems that operate as prenavigation tools can assist such individuals. This mixed-methods study examined the effectiveness of an interactive audio-tactile map tool on the process of cognitive mapping and recall, among people who were blind or had visual impairments. The tool was developed with the involvement of visually impaired individuals who additionally provided further feedback throughout this research.

METHODS

A mixed-methods experimental design was employed. Fourteen participants were allocated to either an experimental group who were exposed to an audio-tactile map, or a control group exposed to a verbally annotated tactile map. After five minutes' exposure, multiple-choice questions examined participants' recall of the spatial and navigational content. Subsequent semi-structured interviews were conducted to examine their views surrounding the study and the product.

RESULTS

The experimental condition had significantly better overall recall than the control group and higher average scores in all four areas examined by the questions. The interviews suggested that the interactive component offered individuals the freedom to learn the map in several ways and did not restrict them to a sequential and linear approach to learning.

CONCLUSION

Assistive technology can reduce challenges faced by people with visual impairments, and the flexible learning approach offered by the audio-tactile map may be of particular value. Future researchers and assistive technology developers may wish to explore this further.

Discriminable Height Differences of Raised Lines

Introduction:

The purpose of this study was to determine the discriminable height differences of raised lines printed on paper, as assessed by people who are blind, with or without years of tactile experience.

Methods:

Ten younger and 10 older tactile readers with blindness and with rich tactile experience; and 10 blindfolded, older, sighted participants with little tactile experience discriminated paired raised-line stimuli of different heights using the fingers of their preferred hand by active touch in a psychophysical experiment.

Results:

There was a significant main effect of the height of the stimulus, F(2, 54) = 56.446, MS = .060, p < .001, [Formula: see text] = .676, [Formula: see text] = .341, and participant group, F(2, 27) = 13.717, MS = .064, p < .001, [Formula: see text] = .504, [Formula: see text] = .357; however, there was no significant main effect of the width of the lines, or any interactions. The younger and older tactile readers had virtually similar thresholds and Weber fractions, and they could discriminate paired stimuli more accurately and efficiently than the older, sighted participants. We provided the discriminable height data of the raised lines based on the mean and 95th percentile values of the Weber fractions.

Discussion:

The results indicate the importance of tactile experiences for height discrimination in active touch. For older persons with recently developed blindness, raised lines with larger height differences should be used.

Information for practitioners:

These data will be helpful for developing new braille embossers that can print raised-line graphics for people with visual impairments, with or without years of tactile experience.

Emotion Measurements Through the Touch of Materials Surfaces

The emotion generated by the touch of materials is studied via a protocol based on blind assessment of various stimuli. The human emotional reaction felt toward a material is estimated through (i) explicit measurements, using a questionnaire collecting valence and intensity, and (ii) implicit measurements of the activity of the autonomic nervous system, via a pupillometry equipment. A panel of 25 university students (13 women, 12 men), aged from 18 to 27, tested blind twelve materials such as polymers, sandpapers, wood, velvet and fur, randomly ordered. After measuring the initial pupil diameter, taken as a reference, its variation during the tactile exploration was recorded. After each touch, the participants were asked to quantify the emotional value of the material. The results show that the pupil size variation follows the emotional intensity. It is significantly larger during the touch of materials considered as pleasant or unpleasant, than with the touch of neutral materials. Moreover, after a time period of about 0.5 s following the stimulus, the results reveal significant differences between pleasant and unpleasant stimuli, as well as differences according to gender, i.e., higher pupil dilatation of women than men. These results suggest (i) that the autonomic nervous system is initially sensitive to high arousing stimulation, and (ii) that, after a certain period, the pupil size changes according to the cognitive interest induced and the emotional regulation adopted. This research shows the interest of the emotional characterization of materials for product design.

Preserved tactile acuity in older pianists

A previous study from our lab demonstrated retention of high tactile acuity throughout the lifespan in blind subjects in contrast to the typical decline found for sighted subjects (Legge, Madison, Vaughn, Cheong & Miller, Percept Psychophys, 70 (8), 1471-1488, 2008). We hypothesize that preserved tactile acuity in old age is due to lifelong experience with focused attention to touch and not to blindness per se. Proficient pianists devote attention to touch - fingerings and dynamics - over years of practice. To test our hypothesis, we measured tactile acuity in groups of ten young (mean age 24.5 years) and 11 old (mean age 64.7 years) normally sighted pianists and compared their results to the blind and sighted subjects in our 2008 study. The pianists, like the subjects in 2008, were tested on two tactile-acuity charts requiring active touch, one composed of embossed Landolt rings and the other composed of dot patterns similar to braille. For both tests, the pianists performed more like the blind subjects than the sighted subjects from our 2008 study. For the ring chart, there was no significant difference in tactile acuity between the young and old pianists and no significant difference between the pianists and the blind subjects. For the dot chart, the pianists showed an age-related decline in tactile acuity, but not as severe as the sighted subjects from 2008. Our results are consistent with the hypothesis that lifelong experience with focused attention to touch acts to preserve tactile acuity into old age for both blind and sighted subjects.

Hand-Feel Touch Cues and Their Influences on Consumer Perception and Behavior with Respect to Food Products: A Review

There has been a great deal of research investigating intrinsic/extrinsic cues and their influences on consumer perception and purchasing decisions at points of sale, product usage, and consumption. Consumers create expectations toward a food product through sensory information extracted from its surface (intrinsic cues) or packaging (extrinsic cues) at retail stores. Packaging is one of the important extrinsic cues that can modulate consumer perception, liking, and decision making of a product. For example, handling a product packaging during consumption, even just touching the packaging while opening or holding it during consumption, may result in a consumer expectation of the package content. Although hand-feel touch cues are an integral part of the food consumption experience, as can be observed in such an instance, little has been known about their influences on consumer perception, acceptability, and purchase behavior of food products. This review therefore provided a better understanding about hand-feel touch cues and their influences in the context of food and beverage experience with a focus on (1) an overview of touch as a sensory modality, (2) factors influencing hand-feel perception, (3) influences of hand-feel touch cues on the perception of other sensory modalities, and (4) the effects of hand-feel touch cues on emotional responses and purchase behavior.

Diagnostic Accuracy of Breast Medical Tactile Examiners (MTEs): A Prospective Pilot Study

Background

The usefulness of clinical breast examination (CBE) in general and in breast cancer screening programs has been a matter of debate. This study investigated whether adding vision-impaired medical tactile examiners (MTEs) improves the predictiveness of CBE for suspicious lesions and analyzed the feasibility and acceptability of this approach.

Methods

The prospective study included 104 patients. Physicians and MTEs performed CBEs, and mammography and ultrasound results were used as the gold standard. Sensitivity and specificity were calculated and logistic regression models were used to compare the predictive value of CBE by physicians alone, MTEs alone, and physicians and MTEs combined.

Results

For CBEs by physicians alone, MTEs alone, and both combined, sensitivity was 71, 82, and 89% and specificity was 55, 45, and 35%, respectively. Using adjusted logistic regression models, the validated areas under the curve were 0.685, 0.692, and 0.710 (median bootstrapped p value (DeLong) = 0.381).

Conclusion

The predictive value for a suspicious breast lesion in CBEs performed by MTEs in patients without prior surgery was similar to that of physician-conducted CBEs. Including MTEs in the CBE procedure in breast units thus appears feasible and could be a way of utilizing their skills.

Improved balance performance accompanied by structural plasticity in blind adults after training

Postural control requires the sensory integration of visual, vestibular, and proprioceptive signals. In the absence of vision, either by blindfolding or in blind individuals, balance performance is typically poorer than with sight. Previous research has suggested that despite showing compensatory vestibular and proprioceptive processing during upright standing, balance performance in blind individuals is overall lower than in sighted controls with eyes open. The present study tested whether balance training, which places demands on vestibular and proprioceptive self-motion perception, improves balance performance in blind adults, and whether we find similar structural correlates in cortical and subcortical brain areas as have been reported in sighted individuals. Fourteen congenitally or late blind adults were randomly assigned to either a balance or a relaxation group and exercised twice a week for 12 weeks. Assessments prior to and after training included balance tests and the acquisition of T1-weighted MRI images. The blind balance group significantly improved in dynamic, static, and functional balance performance compared to the blind relaxation group. The balance performance improvement did not differ from that of age- and gender matched sighted adults after balance training. Cortical thickness increased in the left parahippocampus and decreased in the inferior insula bilaterally in the blind balance group compared to the blind relaxation group. Thickness decreases in the insula were related to improved static and functional balance. Gray matter volume was reduced in the left hippocampus proper and increased in the right subiculum in the blind balance group. The present data suggest that impaired balance performance in blind adults can be significantly improved by a training inducing plasticity in brain regions associated with vestibular and proprioceptive self-motion processing.

Do People who Became Blind Early in Life Develop a Better Sense of Smell? A Psychophysical Study

Using a set of psychophysical tests, we compared the olfactory abilities of 8 persons who became blind early in life and 16 sighted persons in a control group who were matched for age, sex, and handedness. The results indicated that those who became blind early in life developed compensatory perceptual mechanisms in the olfactory domain that involve basic sensory processes, such as the detection of odors.

Edge orientation perception during active touch

Previous studies investigating the perceptual attributes of tactile edge orientation processing have applied their stimuli to an immobilized fingertip. Here we tested the perceptual attributes of edge orientation processing when participants actively touched the stimulus. Our participants moved their finger over two pairs of edges, one pair parallel and the other nonparallel to varying degrees, and were asked to identify which of the two pairs was nonparallel. In addition to the psychophysical estimates of edge orientation acuity, we measured the speed at which participants moved their finger and the forces they exerted when moving their finger over the stimulus. We report four main findings. First, edge orientation acuity during active touch averaged 12.4°, similar to that previously reported during passive touch. Second, on average, participants moved their finger over the stimuli at ~20 mm/s and exerted contact forces of ~0.3 N. Third, there was no clear relationship between how people moved their finger or how they pressed on the stimulus and their edge orientation acuity. Fourth, consistent with previous work testing tactile spatial acuity, we found a significant correlation between fingertip size and orientation acuity such that people with smaller fingertips tended to have better orientation acuity. NEW & NOTEWORTHY Edge orientation acuity expressed by the motor system during manipulation is many times better than edge orientation acuity assessed in psychophysical studies where stimuli are applied to a passive fingertip. Here we show that this advantage is not because of movement per se because edge orientation acuity assessed in a psychophysical task, where participants actively move their finger over the stimuli, yields results similar to previous passive psychophysical studies.

Cortical Plasticity and Olfactory Function in Early Blindness

Over the last decade, functional brain imaging has provided insight to the maturation processes and has helped elucidate the pathophysiological mechanisms involved in brain plasticity in the absence of vision. In case of congenital blindness, drastic changes occur within the deafferented “visual” cortex that starts receiving and processing non visual inputs, including olfactory stimuli. This functional reorganization of the occipital cortex gives rise to compensatory perceptual and cognitive mechanisms that help blind persons achieve perceptual tasks, leading to superior olfactory abilities in these subjects. This view receives support from psychophysical testing, volumetric measurements and functional brain imaging studies in humans, which are presented here.

A Performance Comparison of On-Hand versus On-Phone Nonvisual Input by Blind and Sighted Users

On-body interaction, in which the user employs one's own body as an input surface, has the potential to provide efficient mobile computing access for blind users. It offers increased tactile and proprioceptive feedback compared to a phone and, because it is always available, it should allow for quick audio output control without having to retrieve the phone from a pocket or bag. Despite this potential, there has been little investigation of on-body input for users with visual impairments. To assess blind users’ performance with on-body input versus touchscreen input, we conducted a controlled lab study with 12 sighted and 11 blind participants. Study tasks included basic pointing and drawing more complex shape gestures. Our findings confirm past work with sighted users showing that the hand results in faster pointing than the phone. Most important, we also show that: (1) the performance gain of the hand applies to blind users as well, (2) the accuracy of where the pointing finger first lands is higher with the hand than the phone, (3) on-hand pointing performance is affected by the location of targets, and (4) shape gestures drawn on the hand result in higher gesture recognition rates than those on the phone. Our findings highlight the potential of on-body input to support accessible nonvisual mobile computing.

Designing Media for Visually-Impaired Users of Refreshable Touch Displays: Possibilities and Pitfalls

This paper discusses issues of importance to designers of media for visually impaired users. The paper considers the influence of human factors on the effectiveness of presentation as well as the strengths and weaknesses of tactile, vibrotactile, haptic, and multimodal methods of rendering maps, graphs, and models. The authors, all of whom are visually impaired researchers in this domain, present findings from their own work and work of many others who have contributed to the current understanding of how to prepare and render images for both hard-copy and technology-mediated presentation of Braille and tangible graphics.

Differences in two-point discrimination and sensory threshold in the blind between braille and text reading: a pilot study

[Purpose] This study investigated two-point discrimination (TPD) and the electrical sensory threshold of the blind to define the effect of using Braille on the tactile and electrical senses. [Subjects and Methods] Twenty-eight blind participants were divided equally into a text-reading and a Braille-reading group. We measured tactile sensory and electrical thresholds using the TPD method and a transcutaneous electrical nerve stimulator. [Results] The left palm TPD values were significantly different between the groups. The values of the electrical sensory threshold in the left hand, the electrical pain threshold in the left hand, and the electrical pain threshold in the right hand were significantly lower in the Braille group than in the text group. [Conclusion] These findings make it difficult to explain the difference in tactility between groups, excluding both palms. However, our data show that using Braille can enhance development of the sensory median nerve in the blind, particularly in terms of the electrical sensory and pain thresholds.

Olfactory Function Assessment of Blind Subjects Using the Sniffin' Sticks Test

OBJECTIVE

In recent years, a growing number of studies have focused on the olfactory abilities of blind individuals as well as their tactile and auditory senses. In this study, we aimed to investigate possible alterations in the sense of smell in early- and late-blind subjects as compared with sighted controls, using a Sniffin' Sticks test battery.

STUDY DESIGN

Prospective clinical study.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

A total of 66 subjects were included in the study. The subjects were divided into 2 groups: blind subjects-who were then subgrouped as subjects with congenital blindness (n = 17) and those with acquired blindness (n = 16)-and sighted subjects (n = 33). We compared both congenitally and acquired blind subjects with sighted counterparts using the Sniffin' Sticks test for odor threshold, odor discrimination, odor identification, and total odor scores.

RESULTS

The blind subjects were more successful than their sighted counterparts in odor discrimination and odor threshold tasks. There was no statistically significant difference between the blind participants and the sighted individuals in terms of odor identification value. Another important finding was that the difference between individuals with congenital blindness and those with acquired blindness was not significant in any of the parameters.

CONCLUSION

This finding may suggest that odor discrimination and odor threshold in blind people were superior to those of controls. There was no difference in any of the results of tasks among congenital and acquired blind subjects.

Correlation of vision loss with tactile-evoked V1 responses in retinitis pigmentosa

Neuroimaging studies have shown that the visual cortex of visually impaired humans is active during tactile tasks. We sought to determine if this cross-modal activation in the primary visual cortex is correlated with vision loss in individuals with retinitis pigmentosa (RP), an inherited degenerative photoreceptor disease that progressively diminishes vision later in life. RP and sighted subjects completed three tactile tasks: a symmetry discrimination task, a Braille-dot counting task, and a sandpaper roughness discrimination task. We measured tactile-evoked blood oxygenation level dependent (BOLD) responses using functional magnetic resonance imaging (fMRI). For each subject, we quantified the cortical extent of the tactile-evoked response by the proportion of modulated voxels within the primary visual cortex (V1) and its strength by the mean absolute modulation amplitude of the modulated voxels. We characterized vision loss in terms of visual acuity and the areal proportion of V1 that corresponds to the preserved visual field. Visual acuity and proportion of the preserved visual field both had a highly significant effect on the cortical extent of the V1 BOLD response to tactile stimulation, while visual acuity also had a significant effect on the strength of the V1 response. These effects of vision loss on cross-modal responses were reliable despite high inter-subject variability. Controlling for task-evoked responses in the primary somatosensory cortex (S1) across subjects further strengthened the effects of vision loss on cross-model responses in V1. We propose that such cross-modal responses in V1 and other visual areas may be used as a cortically localized biomarker to account for individual differences in visual performance following sight recovery treatments.

The science of spinal motion palpation: a review and update with implications for assessment and intervention

Spinal motion palpation (SMP) is a standard component of a manual therapy examination despite questionable reliability. The present research is inconclusive as to the relevance of the findings from SMP, with respect to the patient's pain complaints. Differences in the testing methods and interpretation of spinal mobility testing are problematic. If SMP is to be a meaningful component of a spinal examination, the methods for testing and interpretation must be carefully scrutinized. The intent of this narrative review is to facilitate a better understanding of how SMP should provide the examiner with relevant information for assessment and treatment of patients with spinal pain disorders. The concept of just noticeable difference is presented and applied to SMP as a suggestion for determining the neutral zone behavior of a spinal segment. In addition, the use of a lighter, or more passive receptive palpation technique, is considered as a means for increasing tactile discrimination of spinal movement behavior. Further understanding of the scientific basis of testing SMP may improve intra- and inter-examiner reliability. The significance of the findings from SMP should be considered in context of the patient's functional problem. Methodological changes may be indicated for the performance of SMP techniques, such as central posterior-anterior (PA) pressure and passive intervertebral motion tests, in order to improve reliability. Instructors of manual therapy involved in teaching SMP should be knowledgeable of the neurophysiological processes of touch sensation so as to best advise students in the application of the various testing techniques.

Tactile spatial acuity in childhood: effects of age and fingertip size

Tactile acuity is known to decline with age in adults, possibly as the result of receptor loss, but less is understood about how tactile acuity changes during childhood. Previous research from our laboratory has shown that fingertip size influences tactile spatial acuity in young adults: those with larger fingers tend to have poorer acuity, possibly because mechanoreceptors are more sparsely distributed in larger fingers. We hypothesized that a similar relationship would hold among children. If so, children’s tactile spatial acuity might be expected to worsen as their fingertips grow. However, concomitant CNS maturation might result in more efficient perceptual processing, counteracting the effect of fingertip growth on tactile acuity. To investigate, we conducted a cross-sectional study, testing 116 participants ranging in age from 6 to 16 years on a precision-controlled tactile grating orientation task. We measured each participant's grating orientation threshold on the dominant index finger, along with physical properties of the fingertip: surface area, volume, sweat pore spacing, and temperature. We found that, as in adults, children with larger fingertips (at a given age) had significantly poorer acuity, yet paradoxically acuity did not worsen significantly with age. We propose that finger growth during development results in a gradual decline in innervation density as receptive fields reposition to cover an expanding skin surface. At the same time, central maturation presumably enhances perceptual processing.

A physical constraint on perceptual learning: tactile spatial acuity improves with training to a limit set by finger size

In touch as in vision, perceptual acuity improves with training to an extent that differs greatly across people; even individuals with similar initial acuity may undergo markedly different improvement with training. What accounts for this variability in perceptual learning? We hypothesized that a simple physical characteristic, fingertip surface area, might constrain tactile learning, because previous research suggests that larger fingers have more widely spaced mechanoreceptors. To test our hypothesis, we trained 10 human participants intensively on a tactile spatial acuity task. During 4 d, participants completed 1900 training trials (38 50-trial blocks) in which they discriminated the orientation of square-wave gratings pressed onto the stationary index or ring finger, with auditory feedback provided to signal correct and incorrect responses. We progressively increased task difficulty by shifting to thinner groove widths whenever participants achieved ≥90% correct block performance. We took optical scans to measure surface area from the distal interphalangeal crease to the tip of the finger. Participants' acuity improved markedly on the trained finger and to a lesser extent on the untrained finger. Crucially, we found that participants' tactile spatial acuity improved toward a theoretical optimum set by their finger size; participants with worse initial performance relative to their finger size improved more with training, and posttraining performance was better correlated than pretraining performance with finger size. These results strongly support the hypothesis that tactile perceptual learning is limited by finger size. We suspect that analogous physical constraints on perceptual learning will be found in other sensory modalities.

Crossmodal recruitment of the ventral visual stream in congenital blindness

We used functional MRI (fMRI) to test the hypothesis that blind subjects recruit the ventral visual stream during nonhaptic tactile-form recognition. Congenitally blind and blindfolded sighted control subjects were scanned after they had been trained during four consecutive days to perform a tactile-form recognition task with the tongue display unit (TDU). Both groups learned the task at the same rate. In line with our hypothesis, the fMRI data showed that during nonhaptic shape recognition, blind subjects activated large portions of the ventral visual stream, including the cuneus, precuneus, inferotemporal (IT), cortex, lateral occipital tactile vision area (LOtv), and fusiform gyrus. Control subjects activated area LOtv and precuneus but not cuneus, IT and fusiform gyrus. These results indicate that congenitally blind subjects recruit key regions in the ventral visual pathway during nonhaptic tactile shape discrimination. The activation of LOtv by nonhaptic tactile shape processing in blind and sighted subjects adds further support to the notion that this area subserves an abstract or supramodal representation of shape. Together with our previous findings, our data suggest that the segregation of the efferent projections of the primary visual cortex into a dorsal and ventral visual stream is preserved in individuals blind from birth.

A genetic basis for mechanosensory traits in humans

Hearing and touch are genetically related, and people with excellent hearing are more likely to have a fine sense of touch and vice versa.

In all vertebrates hearing and touch represent two distinct sensory systems that both rely on the transformation of mechanical force into electrical signals. There is an extensive literature describing single gene mutations in humans that cause hearing impairment, but there are essentially none for touch. Here we first asked if touch sensitivity is a heritable trait and second whether there are common genes that influence different mechanosensory senses like hearing and touch in humans. Using a classical twin study design we demonstrate that touch sensitivity and touch acuity are highly heritable traits. Quantitative phenotypic measures of different mechanosensory systems revealed significant correlations between touch and hearing acuity in a healthy human population. Thus mutations in genes causing deafness genes could conceivably negatively influence touch sensitivity. In agreement with this hypothesis we found that a proportion of a cohort of congenitally deaf young adults display significantly impaired measures of touch sensitivity compared to controls. In contrast, blind individuals showed enhanced, not diminished touch acuity. Finally, by examining a cohort of patients with Usher syndrome, a genetically well-characterized deaf-blindness syndrome, we could show that recessive pathogenic mutations in the USH2A gene influence touch acuity. Control Usher syndrome cohorts lacking demonstrable pathogenic USH2A mutations showed no impairment in touch acuity. Our study thus provides comprehensive evidence that there are common genetic elements that contribute to touch and hearing and has identified one of these genes as USH2A.

In humans many genes have been identified that cause deafness when mutated, but no equivalent genes have been identified that are required for touch. Here, we asked whether genes that influence hearing can also influence touch. Using identical and non-identical human twins it was possible to show that touch performance is substantially influenced by genes. Furthermore, people who have excellent hearing are more likely to have a fine sense of touch and vice versa. Interestingly, people who suffer from congenital deafness have a higher chance of having poor touch performance. In a genetically defined form of human deafness, Usher syndrome type II, a single mutated gene was identified that also impairs touch. Touch and hearing are thus intricately intertwined and there may be other touch/hearing genes waiting to be discovered.

The role of visual experience for the neural basis of spatial cognition

Blindness often results in the adaptive neural reorganization of the remaining modalities, producing sharper auditory and haptic behavioral performance. Yet, non-visual modalities might not be able to fully compensate for the lack of visual experience as in the case of congenital blindness. For example, developmental visual experience seems to be necessary for the maturation of multisensory neurons for spatial tasks. Additionally, the ability of vision to convey information in parallel might be taken into account as the main attribute that cannot be fully compensated by the spared modalities. Therefore, the lack of visual experience might impair all spatial tasks that require the integration of inputs from different modalities, such as having to represent a set of objects on the basis of the spatial relationships among the objects, rather than the spatial relationship that each object has with oneself. Here we integrate behavioral and neural evidence to conclude that visual experience is necessary for the neural development of normal spatial cognition.

Sequential vs simultaneous encoding of spatial information: a comparison between the blind and the sighted

The aim of this research is to assess whether the crucial factor in determining the characteristics of blind people's spatial mental images is concerned with the visual impairment per se or the processing style that the dominant perceptual modalities used to acquire spatial information impose, i.e. simultaneous (vision) vs sequential (kinaesthesis). Participants were asked to learn six positions in a large parking area via movement alone (congenitally blind, adventitiously blind, blindfolded sighted) or with vision plus movement (simultaneous sighted, sequential sighted), and then to mentally scan between positions in the path. The crucial manipulation concerned the sequential sighted group. Their visual exploration was made sequential by putting visual obstacles within the pathway in such a way that they could not see simultaneously the positions along the pathway. The results revealed a significant time/distance linear relation in all tested groups. However, the linear component was lower in sequential sighted and blind participants, especially congenital. Sequential sighted and congenitally blind participants showed an almost overlapping performance. Differences between groups became evident when mentally scanning farther distances (more than 5m). This threshold effect could be revealing of processing limitations due to the need of integrating and updating spatial information. Overall, the results suggest that the characteristics of the processing style rather than the visual impairment per se affect blind people's spatial mental images.

Short-term visual deprivation does not enhance passive tactile spatial acuity

An important unresolved question in sensory neuroscience is whether, and if so with what time course, tactile perception is enhanced by visual deprivation. In three experiments involving 158 normally sighted human participants, we assessed whether tactile spatial acuity improves with short-term visual deprivation over periods ranging from under 10 to over 110 minutes. We used an automated, precisely controlled two-interval forced-choice grating orientation task to assess each participant's ability to discern the orientation of square-wave gratings pressed against the stationary index finger pad of the dominant hand. A two-down one-up staircase (Experiment 1) or a Bayesian adaptive procedure (Experiments 2 and 3) was used to determine the groove width of the grating whose orientation each participant could reliably discriminate. The experiments consistently showed that tactile grating orientation discrimination does not improve with short-term visual deprivation. In fact, we found that tactile performance degraded slightly but significantly upon a brief period of visual deprivation (Experiment 1) and did not improve over periods of up to 110 minutes of deprivation (Experiments 2 and 3). The results additionally showed that grating orientation discrimination tends to improve upon repeated testing, and confirmed that women significantly outperform men on the grating orientation task. We conclude that, contrary to two recent reports but consistent with an earlier literature, passive tactile spatial acuity is not enhanced by short-term visual deprivation. Our findings have important theoretical and practical implications. On the theoretical side, the findings set limits on the time course over which neural mechanisms such as crossmodal plasticity may operate to drive sensory changes; on the practical side, the findings suggest that researchers who compare tactile acuity of blind and sighted participants should not blindfold the sighted participants.

Tactile spatial acuity enhancement in blindness: evidence for experience-dependent mechanisms

Tactile spatial acuity is enhanced in blindness, according to several studies, but the cause of this enhancement has been controversial. Two competing hypotheses are the tactile experience hypothesis (reliance on the sense of touch drives tactile-acuity enhancement) and the visual deprivation hypothesis (the absence of vision itself drives tactile-acuity enhancement). Here, we performed experiments to distinguish between these two hypotheses. We used force-controlled grating orientation tasks to compare the passive (finger stationary) tactile spatial acuity of 28 profoundly blind and 55 normally sighted humans on the index, middle, and ring fingers of each hand, and on the lips. The tactile experience hypothesis predicted that blind participants would outperform the sighted on the fingers, and that Braille reading would correlate with tactile acuity. The visual deprivation hypothesis predicted that blind participants would outperform the sighted on fingers and lips. Consistent with the tactile experience hypothesis, the blind significantly outperformed the sighted on all fingers, but not on the lips. Additionally, among blind participants, proficient Braille readers on their preferred reading index finger outperformed nonreaders. Finally, proficient Braille readers performed better with their preferred reading index finger than with the opposite index finger, and their acuity on the preferred reading finger correlated with their weekly reading time. These results clearly implicate reliance on the sense of touch as the trigger for tactile spatial acuity enhancement in the blind, and suggest the action of underlying experience-dependent neural mechanisms such as somatosensory and/or cross-modal cortical plasticity.

Characterization of human tactile pattern recognition performance at different ages

This study examined tactile pattern recognition performance in human observers (N = 44) in the context of a letter recognition task at the fingertip. Participants were recruited from three different age groups (youth, n = 17; young adults, n = 14; seniors, n = 13) to examine age-related differences in performance. The influence of gender (males vs females) and hand (right vs left) was also examined. Performance was characterized in terms of both response accuracy and associated response times (RTs). Patterns of confusion between letters were also examined. Results showed that age was the most important factor in determining the capacity of our participants to perform fast and accurate pattern recognition. In this respect, younger participants (i.e., youth and young adults) clearly outperformed seniors by showing not only better accuracy and less confusion but also 2-3 times faster RT. By comparison, the combined influence of "hand" and "gender" on recognition performance was only marginal. These results indicate that the ability to perform complex tactile pattern recognition is already well established in youth 10-14 years of age with only minor refinements occurring later in early adulthood. With advancing age, such ability becomes far less efficient, as judged by the drastic increase in RT observed in seniors, in spite of a relatively good accuracy. This suggests that alterations not only at the peripheral receptor level but also at the central processing level might play an important role in limiting the ability of seniors to perform fast and efficient pattern recognition at the fingertip.