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

Child development and the role of visual experience in the use of spatial and non-spatial features in haptic object perception

Previous work has suggested a different developmental timeline and role of visual experience for the use of spatial and non-spatial features in haptic object recognition. To investigate this conjecture, we used a haptic ambiguous odd-one-out task in which one object needed to be selected as being different from two other objects. The odd-one-out could be selected based on four characteristics: size, shape (spatial), texture, and weight (non-spatial). We tested sighted children from 4 to 12 years of age; congenitally blind, late blind, and adult participants with low vision; and normally sighted adults. Given the protracted developmental time course for spatial perception, we expected a shift from a preference for non-spatial features toward spatial features during typical development. Due to the dominant influence of vision for spatial perception, we expected congenitally blind adults to show a similar preference for non-spatial features as the youngest children. The results confirmed our first hypothesis; the 4-year-olds demonstrated a lower dominance for spatial features for object classification compared with older children and sighted adults. In contrast, our second hypothesis was not confirmed; congenitally blind adults' preferred categorization criteria were indistinguishable from those of sighted controls. These findings suggest an early development, but late maturation, of spatial processing in haptic object recognition independent of visual experience.

Adults' spatial scaling of tactile maps: Insights from studying sighted, early and late blind individuals

The current study investigated spatial scaling of tactile maps among blind adults and blindfolded sighted controls. We were specifically interested in identifying spatial scaling strategies as well as effects of different scaling directions (up versus down) on participants' performance. To this aim, we asked late blind participants (with visual memory, Experiment 1) and early blind participants (without visual memory, Experiment 2) as well as sighted blindfolded controls to encode a map including a target and to place a response disc at the same spot on an empty, constant-sized referent space. Maps had five different sizes resulting in five scaling factors (1:3, 1:2, 1:1, 2:1, 3:1), allowing to investigate different scaling directions (up and down) in a single, comprehensive design. Accuracy and speed of learning about the target location as well as responding served as dependent variables. We hypothesized that participants who can use visual mental representations (i.e., late blind and blindfolded sighted participants) may adopt mental transformation scaling strategies. However, our results did not support this hypothesis. At the same time, we predicted the usage of relative distance scaling strategies in early blind participants, which was supported by our findings. Moreover, our results suggested that tactile maps can be scaled as accurately and even faster by blind participants than by sighted participants. Furthermore, irrespective of the visual status, participants of each visual status group gravitated their responses towards the center of the space. Overall, it seems that a lack of visual imagery does not impair early blind adults' spatial scaling ability but causes them to use a different strategy than sighted and late blind individuals.

Altered grid-like coding in early blind people

Cognitive maps in the hippocampal-entorhinal system are central for the representation of both spatial and non-spatial relationships. Although this system, especially in humans, heavily relies on vision, the role of visual experience in shaping the development of cognitive maps remains largely unknown. Here, we test sighted and early blind individuals in both imagined navigation in fMRI and real-world navigation. During imagined navigation, the Human Navigation Network, constituted by frontal, medial temporal, and parietal cortices, is reliably activated in both groups, showing resilience to visual deprivation. However, neural geometry analyses highlight crucial differences between groups. A 60° rotational symmetry, characteristic of a hexagonal grid-like coding, emerges in the entorhinal cortex of sighted but not blind people, who instead show a 90° (4-fold) symmetry, indicative of a square grid. Moreover, higher parietal cortex activity during navigation in blind people correlates with the magnitude of 4-fold symmetry. In sum, early blindness can alter the geometry of entorhinal cognitive maps, possibly as a consequence of higher reliance on parietal egocentric coding during navigation.

Learning and navigating digitally rendered haptic spatial layouts

Learning spatial layouts and navigating through them rely not simply on sight but rather on multisensory processes, including touch. Digital haptics based on ultrasounds are effective for creating and manipulating mental images of individual objects in sighted and visually impaired participants. Here, we tested if this extends to scenes and navigation within them. Using only tactile stimuli conveyed via ultrasonic feedback on a digital touchscreen (i.e., a digital interactive map), 25 sighted, blindfolded participants first learned the basic layout of an apartment based on digital haptics only and then one of two trajectories through it. While still blindfolded, participants successfully reconstructed the haptically learned 2D spaces and navigated these spaces. Digital haptics were thus an effective means to learn and translate, on the one hand, 2D images into 3D reconstructions of layouts and, on the other hand, navigate actions within real spaces. Digital haptics based on ultrasounds represent an alternative learning tool for complex scenes as well as for successful navigation in previously unfamiliar layouts, which can likely be further applied in the rehabilitation of spatial functions and mitigation of visual impairments.

Drawing as a tool for investigating the nature of imagery representations of blind people: The case of the canonical size phenomenon

Several studies have shown that blind people, including those with congenital blindness, can use raised-line drawings, both for "reading" tactile graphics and for drawing unassisted. However, research on drawings produced by blind people has mainly been qualitative. The current experimental study was designed to investigate the under-researched issue of the size of drawings created by people with blindness. Participants (N = 59) varied in their visual status. Adventitiously blind people had previous visual experience and might use visual representations (e.g., when visualising objects in imagery/working memory). Congenitally blind people did not have any visual experience. The participant's task was to draw from memory common objects that vary in size in the real world. The findings revealed that both groups of participants produced larger drawings of objects that have larger actual sizes. This means that the size of familiar objects is a property of blind people's mental representations, regardless of their visual status. Our research also sheds light on the nature of the phenomenon of canonical size. Since we have found the canonical size effect in a group of people who are blind from birth, the assumption of the visual nature of this phenomenon - caused by the ocular-centric biases present in studies on drawing performance - should be revised.

Physical activity and sport practice to improve balance control of visually impaired individuals: a narrative review with future perspectives

Visual disability negatively impacts balance, everyday self-efficacy, and mobility and often leads affected subjects to perceive physical exercise as a burdensome challenge thus discouraging them from practicing. Despite the well-proven benefits of regular physical activity in visually impaired people, especially addressing postural control, there are no specific guidelines and most of the available literature seems to be flawed by critical issues. Given the wide heterogeneity and the multidimensional needs of this population, a more realistic and target-specific perspective is needed in order to properly investigate and promote exercise practice and adherence for balance improvement. On this basis, through a critical overview of the recent literature, the present article aimed to enrich the current knowledge about this topic by providing innovative suggestions, both practical and methodological, and specifically deepening the disability-related deficits and peculiarities of different age ranges. Moreover, since a multidisciplinary approach is advisable when designing and leading exercise protocols tailored to visually impaired individuals, such innovative hints also highlighted the central role of the adapted physical activity specialist, hence contributing to foster its official professional recognition and involvement in this field.

Reactive Agility and Pitching Performance Improvement in Visually Impaired Competitive Italian Baseball Players: An Innovative Training and Evaluation Proposal

Visual input significantly affects kinesthesis skills and, hence, visually impaired individuals show less developed sensorimotor control, especially in an unfamiliar outdoor environment. Regular blind baseball practice can counteract such a deficit but, given the complex kinetic chain model required, a targeted workout proposal is needed to improve the main athletic gesture performance. On these premises, we investigated, for the first time, the running and pitching performance of a competitive Italian blind baseball team through quantitative tools and parameters such as Libra Easytech sensorized proprioceptive board, goniometric active range of motion, chronometric speed, and pitching linear length. Moreover, the perceived physical exertion was assessed by the Borg CR10 scale. Consequently, an adapted athletic training protocol was designed and tested on the field during the competitive season, with the aim to strengthen sport specific-gesture coordination and efficacy as well as to prevent injuries. Quantitative assessments showed an improvement in ankle stability index, bilateral upper limb and hip mobility, reactive agility, running braking phase control during second base approaching, and auditory target-related pitching accuracy along with a decrease in perceived physical exertion. This protocol might therefore represent an effective and easily reproducible training and evaluation approach to tailor management of visually impaired baseball players, and safely improve their athletic performance under the supervision of an adapted exercise specialist.

Cognitive map formation in the blind is enhanced by three-dimensional tactile information

For blind individuals, tactile maps are useful tools to form cognitive maps through touch. However, they still experience challenges in cognitive map formation and independent navigation. Three-dimensional (3D) tactile information is thus increasingly being considered to convey enriched spatial information, but it remains unclear if it can facilitate cognitive map formation compared to traditional two-dimensional (2D) tactile information. Consequently, the present study investigated the impact of the type of sensory input (tactile 2D vs. tactile 3D vs. a visual control condition) on cognitive map formation. To do so, early blind (EB, n = 13), late blind (LB, n = 12), and sighted control (SC, n = 14) participants were tasked to learn the layouts of mazes produced with different sensory information (tactile 2D vs. tactile 3D vs. visual control) and to infer routes from memory. Results show that EB manifested stronger cognitive map formation with 3D mazes, LB performed equally well with 2D and 3D tactile mazes, and SC manifested equivalent cognitive map formation with visual and 3D tactile mazes but were negatively impacted by 2D tactile mazes. 3D tactile maps therefore have the potential to improve spatial learning for EB and newly blind individuals through a reduction of cognitive overload. Installation of 3D tactile maps in public spaces should be considered to promote universal accessibility and reduce blind individuals' wayfinding deficits related to the inaccessibility of spatial information through non-visual means.

Clinical assessment of the TechArm system on visually impaired and blind children during uni- and multi-sensory perception tasks

We developed the TechArm system as a novel technological tool intended for visual rehabilitation settings. The system is designed to provide a quantitative assessment of the stage of development of perceptual and functional skills that are normally vision-dependent, and to be integrated in customized training protocols. Indeed, the system can provide uni- and multisensory stimulation, allowing visually impaired people to train their capability of correctly interpreting non-visual cues from the environment. Importantly, the TechArm is suitable to be used by very young children, when the rehabilitative potential is maximal. In the present work, we validated the TechArm system on a pediatric population of low-vision, blind, and sighted children. In particular, four TechArm units were used to deliver uni- (audio or tactile) or multi-sensory stimulation (audio-tactile) on the participant's arm, and subject was asked to evaluate the number of active units. Results showed no significant difference among groups (normal or impaired vision). Overall, we observed the best performance in tactile condition, while auditory accuracy was around chance level. Also, we found that the audio-tactile condition is better than the audio condition alone, suggesting that multisensory stimulation is beneficial when perceptual accuracy and precision are low. Interestingly, we observed that for low-vision children the accuracy in audio condition improved proportionally to the severity of the visual impairment. Our findings confirmed the TechArm system's effectiveness in assessing perceptual competencies in sighted and visually impaired children, and its potential to be used to develop personalized rehabilitation programs for people with visual and sensory impairments.

Activation of human visual area V6 during egocentric navigation with and without visual experience

V6 is a retinotopic area located in the dorsal visual stream that integrates eye movements with retinal and visuo-motor signals. Despite the known role of V6 in visual motion, it is unknown whether it is involved in navigation and how sensory experiences shape its functional properties. We explored the involvement of V6 in egocentric navigation in sighted and in congenitally blind (CB) participants navigating via an in-house distance-to-sound sensory substitution device (SSD), the EyeCane. We performed two fMRI experiments on two independent datasets. In the first experiment, CB and sighted participants navigated the same mazes. The sighted performed the mazes via vision, while the CB performed them via audition. The CB performed the mazes before and after a training session, using the EyeCane SSD. In the second experiment, a group of sighted participants performed a motor topography task. Our results show that right V6 (rhV6) is selectively involved in egocentric navigation independently of the sensory modality used. Indeed, after training, rhV6 of CB is selectively recruited for auditory navigation, similarly to rhV6 in the sighted. Moreover, we found activation for body movement in area V6, which can putatively contribute to its involvement in egocentric navigation. Taken together, our findings suggest that area rhV6 is a unique hub that transforms spatially relevant sensory information into an egocentric representation for navigation. While vision is clearly the dominant modality, rhV6 is in fact a supramodal area that can develop its selectivity for navigation in the absence of visual experience.

Lack of Visual Experience Affects Multimodal Language Production: Evidence From Congenitally Blind and Sighted People

The human experience is shaped by information from different perceptual channels, but it is still debated whether and how differential experience influences language use. To address this, we compared congenitally blind, blindfolded, and sighted people's descriptions of the same motion events experienced auditorily by all participants (i.e., via sound alone) and conveyed in speech and gesture. Comparison of blind and sighted participants to blindfolded participants helped us disentangle the effects of a lifetime experience of being blind versus the task-specific effects of experiencing a motion event by sound alone. Compared to sighted people, blind people's speech focused more on path and less on manner of motion, and encoded paths in a more segmented fashion using more landmarks and path verbs. Gestures followed the speech, such that blind people pointed to landmarks more and depicted manner less than sighted people. This suggests that visual experience affects how people express spatial events in the multimodal language and that blindness may enhance sensitivity to paths of motion due to changes in event construal. These findings have implications for the claims that language processes are deeply rooted in our sensory experiences.

Early visual deprivation disrupts the mental representation of numbers in visually impaired children

Several shreds of evidence indicate that visual deprivation does not alter numerical competence neither in adults nor in children. However, studies reporting non-impaired numerical abilities in the visually impaired population present some limitations: (a) they mainly assessed the ability to process numbers (e.g. mathematical competence) rather than represent numbers (e.g. mental number line); (b) they principally focused on positive rather than negative number estimates; (c) they investigated numerical abilities in adult individuals except one focusing on children (Crollen et al. in Cognition 210:104586, 2021). Overall, this could limit a comprehensive explanation of the role exerted by vision on numerical processing when vision is compromised. Here we investigated how congenital visual deprivation affects the ability to represent positive and negative numbers in horizontal and sagittal planes in visually impaired children (thirteen children with low vision, eight children with complete blindness, age range 6-15 years old). We adapted the number-to-position paradigm adopted by Crollen et al. (Cognition 210:104586, 2021), asking children to indicate the spatial position of positive and negative numbers on a graduated rule positioned horizontally or sagittally in the frontal plane. Results suggest that long-term visual deprivation alters the ability to identify the spatial position of numbers independently of the spatial plane and the number polarity. Moreover, results indicate that relying on poor visual acuity is detrimental for low vision children when asked to localize both positive and negative numbers in space, suggesting that visual experience might have a differential role in numerical processing depending on number polarity. Such findings add knowledge related to the impact of visual experience on numerical processing. Since both positive and negative numbers are fundamental aspects of learning mathematical principles, the outcomes of the present study inform about the need to implement early rehabilitation strategies to prevent the risk of numerical difficulties in visually impaired children.

Neural substrates of spatial processing and navigation in blindness: An activation likelihood estimation meta-analysis

Even though vision is considered the best suited sensory modality to acquire spatial information, blind individuals can form spatial representations to navigate and orient themselves efficiently in space. Consequently, many studies support the amodality hypothesis of spatial representations since sensory modalities other than vision contribute to the formation of spatial representations, independently of visual experience and imagery. However, given the high variability in abilities and deficits observed in blind populations, a clear consensus about the neural representations of space has yet to be established. To this end, we performed a meta-analysis of the literature on the neural correlates of spatial processing and navigation via sensory modalities other than vision, like touch and audition, in individuals with early and late onset blindness. An activation likelihood estimation (ALE) analysis of the neuroimaging literature revealed that early blind individuals and sighted controls activate the same neural networks in the processing of non-visual spatial information and navigation, including the posterior parietal cortex, frontal eye fields, insula, and the hippocampal complex. Furthermore, blind individuals also recruit primary and associative occipital areas involved in visuo-spatial processing via cross-modal plasticity mechanisms. The scarcity of studies involving late blind individuals did not allow us to establish a clear consensus about the neural substrates of spatial representations in this specific population. In conclusion, the results of our analysis on neuroimaging studies involving early blind individuals support the amodality hypothesis of spatial representations.

Flexible cue anchoring strategies enable stable head direction coding in both sighted and blind animals

Vision plays a crucial role in instructing the brain’s spatial navigation systems. However, little is known about how vision loss affects the neuronal encoding of spatial information. Here, recording from head direction (HD) cells in the anterior dorsal nucleus of the thalamus in mice, we find stable and robust HD tuning in rd1 mice, a model of photoreceptor degeneration, that go blind by approximately one month of age. In contrast, placing sighted animals in darkness significantly impairs HD cell tuning. We find that blind mice use olfactory cues to maintain stable HD tuning and that prior visual experience leads to refined HD cell tuning in blind rd1 adult mice compared to congenitally blind animals. Finally, in the absence of both visual and olfactory cues, the HD attractor network remains intact but the preferred firing direction of HD cells drifts over time. These findings demonstrate flexibility in how the brain uses diverse sensory information to generate a stable directional representation of space.

Vision plays an important role in the head direction cell system in animals. Here the authors recorded from head direction cells in rd1 mice that show retinal degeneration at 1 month, and find that they use smell cues to maintain stable HD tuning.

Chinese Children with Congenital and Acquired Blindness Represent Concrete Concepts in Vertical Space through Tactile Perception

Many studies have tested perceptual symbols in conceptual processing and found that perceptual symbols contain experiences from multisensory channels. However, whether the disability of one sensory channel affects the processing of the perceptual symbols and then affects conceptual processing is still unknown. This line of research would extend the perceptual symbol theory and have implications for language rehabilitation and mental health for people with disabilities. Therefore, the present study filled in this gap and tested whether Chinese children with congenital and acquired blindness have difficulty in recruiting perceptual symbols in the processing of concrete concepts. Experiment 1 used the word-pair-matching paradigm to test whether blind children used vertical space information in understanding concrete word pairs. Experiment 2 used the word-card-pairing paradigm to test the role of tactile experiences in the processing of concrete concepts for blind children. Results found that blind children automatically activated the spatial information of referents in the processing of concepts through the tactile sensory channel even when the visual sensory channel was disabled. This finding supported the compensatory phenomenon of other sensory channels in conceptual representation. In addition, the difference between elementary school blind children and middle school blind children in judging the spatial position of concrete words also indicated the vital influence of perceptual experiences on perceptual symbols in conceptual representation. Interestingly, there were no significant differences between children with congenital or acquired blindness. This might suggest that the compensatory of other sensory channels did not have a sensitive period. This study not only provided new evidence for the perceptual symbol theory but also found that perceptual symbols could be developed by a compensatory mechanism. This compensatory mechanism can be used to develop a rehabilitation program for improving language learning in blind children. Improved language ability in blind children will also improve their mental health problems caused by difficulties in social interaction (e.g., social anxiety).

Cognitive map formation supported by auditory, haptic, and multimodal information in persons with blindness

For efficient navigation, the brain needs to adequately represent the environment in a cognitive map. In this review, we sought to give an overview of literature about cognitive map formation based on non-visual modalities in persons with blindness (PWBs) and sighted persons. The review is focused on the auditory and haptic modalities, including research that combines multiple modalities and real-world navigation. Furthermore, we addressed implications of route and survey representations. Taking together, PWBs as well as sighted persons can build up cognitive maps based on non-visual modalities, although the accuracy sometime somewhat differs between PWBs and sighted persons. We provide some speculations on how to deploy information from different modalities to support cognitive map formation. Furthermore, PWBs and sighted persons seem to be able to construct route as well as survey representations. PWBs can experience difficulties building up a survey representation, but this is not always the case, and research suggests that they can acquire this ability with sufficient spatial information or training. We discuss possible explanations of these inconsistencies.

Motor Influence in Developing Auditory Spatial Cognition in Hemiplegic Children with and without Visual Field Disorder

Spatial representation is a crucial skill for everyday interaction with the environment. Different factors seem to influence spatial perception, such as body movements and vision. However, it is still unknown if motor impairment affects the building of simple spatial perception. To investigate this point, we tested hemiplegic children with (HV) and without visual field (H) disorders in an auditory and visual-spatial localization and pitch discrimination task. Fifteen hemiplegic children (nine H and six HV) and twenty with typical development took part in the experiment. The tasks consisted in listening to a sound coming from a series of speakers positioned at the front or back of the subject. In one condition, subjects were asked to discriminate the pitch, while in the other, subjects had to localize the position of the sound. We also replicated the spatial task in a visual modality. Both groups of hemiplegic children performed worse in the auditory spatial localization task compared with the control, while no difference was found in the pitch discrimination task. For the visual-spatial localization task, only HV children differed from the two other groups. These results suggest that movement is important for the development of auditory spatial representation.

Cognitive map formation through tactile map navigation in visually impaired and sighted persons

The human brain can form cognitive maps of a spatial environment, which can support wayfinding. In this study, we investigated cognitive map formation of an environment presented in the tactile modality, in visually impaired and sighted persons. In addition, we assessed the acquisition of route and survey knowledge. Ten persons with a visual impairment (PVIs) and ten sighted control participants learned a tactile map of a city-like environment. The map included five marked locations associated with different items. Participants subsequently estimated distances between item pairs, performed a direction pointing task, reproduced routes between items and recalled item locations. In addition, we conducted questionnaires to assess general navigational abilities and the use of route or survey strategies. Overall, participants in both groups performed well on the spatial tasks. Our results did not show differences in performance between PVIs and sighted persons, indicating that both groups formed an equally accurate cognitive map. Furthermore, we found that the groups generally used similar navigational strategies, which correlated with performance on some of the tasks, and acquired similar and accurate route and survey knowledge. We therefore suggest that PVIs are able to employ a route as well as survey strategy if they have the opportunity to access route-like as well as map-like information such as on a tactile map.

Navigable Space and Traversable Edges Differentially Influence Reorientation in Sighted and Blind Mice

Reorientation enables navigators to regain their bearings after becoming lost. Disoriented individuals primarily reorient themselves using the geometry of a layout, even when other informative cues, such as landmarks, are present. Yet the specific strategies that animals use to determine geometry are unclear. Moreover, because vision allows subjects to rapidly form precise representations of objects and background, it is unknown whether it has a deterministic role in the use of geometry. In this study, we tested sighted and congenitally blind mice (Ns = 8-11) in various settings in which global shape parameters were manipulated. Results indicated that the navigational affordances of the context-the traversable space-promote sampling of boundaries, which determines the effective use of geometric strategies in both sighted and blind mice. However, blind animals can also effectively reorient themselves using 3D edges by extensively patrolling the borders, even when the traversable space is not limited by these boundaries.

Survey on Psychological Well-Being and Quality of Life in Visually Impaired Individuals: Dancesport vs. Other Sound Input-Based Sports

Sport practice has the widely demonstrated potential of promoting well-being and physical/mental health, especially in disabled individuals. Nowadays, visually impaired people can participate in several sports commonly adapted and played substituting visual input with auditory or tactile ones. By integrating movement and music, dance can simultaneously promote physical and emotional involvement and enhances vicarious sense recruitment. On these premises, we performed a survey to assess the psychological well-being (PWB) and quality of life (QoL) in visually impaired athletes, comparing dancesport vs other sound input-based sports. Twenty-one visually impaired dancers and twenty-seven visually impaired athletes practicing adapted baseball, showdown, blind futsal, or blind tennis completed a structured self-report survey including the Italian version of PWB-18 scale and the Short Form-12 (SF-12) questionnaire. Dancers reported significantly higher scores in PWB-18 autonomy, environmental mastery, and self-acceptance along with a higher PWB total score than the other athlete group. Similarly, the SF-12 questionnaire results demonstrated significantly higher scores in both physical and mental QoL of visually impaired dancers compared with other athletes. In conclusion, our findings suggest that, given its peculiarities, the practice of dancesport may have a stronger positive impact on PWB and QoL of visually impaired individuals than other sound input-based sports.

Deprivation of Auditory Experience Influences Numerosity Discrimination, but Not Numerosity Estimation

Number sense is the ability to estimate the number of items, and it is common to many species. Despite the numerous studies dedicated to unveiling how numerosity is processed in the human brain, to date, it is not clear whether the representation of numerosity is supported by a single general mechanism or by multiple mechanisms. Since it is known that deafness entails a selective impairment in the processing of temporal information, we assessed the approximate numerical abilities of deaf individuals to disentangle these two hypotheses. We used a numerosity discrimination task (2AFC) and an estimation task, in both cases using sequential (temporal) or simultaneous (spatial) stimuli. The results showed a selective impairment of the deaf participants compared with the controls (hearing) in the temporal numerosity discrimination task, while no difference was found to discriminate spatial numerosity. Interestingly, the deaf and hearing participants did not differ in spatial or temporal numerosity estimation. Overall, our results suggest that the deficit in temporal processing induced by deafness also impacts perception in other domains such as numerosity, where sensory information is conveyed in a temporal format, which further suggests the existence of separate mechanisms subserving the processing of temporal and spatial numerosity.

Spatial perspective-taking: insights from sensory impairments

Information can be perceived from a multiplicity of spatial perspectives, which is central to effectively understanding and interacting with our environment and other people. Sensory impairments such as blindness are known to impact spatial representations and perspective-taking is often thought of as a visual process. However, disturbed functioning of other sensory systems (e.g., vestibular, proprioceptive and auditory) can also influence spatial perspective-taking. These lines of research remain largely separate, yet together they may shed new light on the role that each sensory modality plays in this core cognitive ability. The findings to date reveal that spatial cognitive processes may be differently affected by various types of sensory loss. The visual system may be crucial for the development of efficient allocentric (object-to-object) representation; however, the role of vision in adopting another's spatial perspective remains unclear. On the other hand, the vestibular and the proprioceptive systems likely play an important role in anchoring the perceived self to the physical body, thus facilitating imagined self-rotations required to adopt another's spatial perspective. Findings regarding the influence of disturbed auditory functioning on perspective-taking are so far inconclusive and thus await further data. This review highlights that spatial perspective-taking is a highly plastic cognitive ability, as the brain is often able to compensate in the face of different sensory loss.

How ageing and blindness affect egocentric and allocentric spatial memory

Egocentric (subject-to-object) and allocentric (object-to-object) spatial reference frames are fundamental for representing the position of objects or places around us. The literature on spatial cognition in blind people has shown that lack of vision may limit the ability to represent spatial information in an allocentric rather than egocentric way. Furthermore, much research with sighted individuals has reported that ageing has a negative impact on spatial memory. However, as far as we know, no study has assessed how ageing may affect the processing of spatial reference frames in individuals with different degrees of visual experience. To fill this gap, here we report data from a cross-sectional study in which a large sample of young and elderly participants (160 participants in total) who were congenitally blind (long-term visual deprivation), adventitiously blind (late onset of blindness), blindfolded sighted (short-term visual deprivation) and sighted (full visual availability) performed a spatial memory task that required egocentric/allocentric distance judgements with regard to memorised stimuli. The results showed that egocentric judgements were better than allocentric ones and above all that the ability to process allocentric information was influenced by both age and visual status. Specifically, the allocentric judgements of congenitally blind elderly participants were worse than those of all other groups. These findings suggest that ageing and congenital blindness can contribute to the worsening of the ability to represent spatial relationships between external, non-body-centred anchor points.

Using your nose to find your way: Ethological comparisons between human and non-human species

Olfaction is arguably the least valued among our sensory systems, and its significance for human behavior is often neglected. Spatial navigation represents no exception to the rule: humans are often characterized as purely visual navigators, a view that undermines the contribution of olfactory cues. Accordingly, research investigating whether and how humans use olfaction to navigate space is rare. In comparison, research on olfactory navigation in non-human species is abundant, and identifies behavioral strategies along with neural mechanisms characterizing the use of olfactory cues during spatial tasks. Using an ethological approach, our review draws from studies on olfactory navigation across species to describe the adaptation of strategies under the influence of selective pressure. Mammals interact with spatial environments by abstracting multisensory information into cognitive maps. We thus argue that olfactory cues, alongside inputs from other sensory modalities, play a crucial role in spatial navigation for mammalian species, including humans; that is, odors constitute one of the many building blocks in the formation of cognitive maps.

Allocentric spatial perception through vision and touch in sighted and blind children

Vision and touch play a critical role in spatial development, facilitating the acquisition of allocentric and egocentric frames of reference, respectively. Previous works have shown that children's ability to adopt an allocentric frame of reference might be impaired by the absence of visual experience during growth. In the current work, we investigated whether visual deprivation also impairs the ability to shift from egocentric to allocentric frames of reference in a switching-perspective task performed in the visual and haptic domains. Children with and without visual impairments from 6 to 13 years of age were asked to visually (only sighted children) or haptically (blindfolded sighted children and blind children) explore and reproduce a spatial configuration of coins by assuming either an egocentric perspective or an allocentric perspective. Results indicated that temporary visual deprivation impaired the ability of blindfolded sighted children to switch from egocentric to allocentric perspective more in the haptic domain than in the visual domain. Moreover, results on visually impaired children indicated that blindness did not impair allocentric spatial coding in the haptic domain but rather affected the ability to rely on haptic egocentric cues in the switching-perspective task. Finally, our findings suggested that the total absence of vision might impair the development of an egocentric perspective in case of body midline-crossing targets.

Core knowledge of geometry can develop independently of visual experience

Geometrical intuitions spontaneously drive visuo-spatial reasoning in human adults, children and animals. Is their emergence intrinsically linked to visual experience, or does it reflect a core property of cognition shared across sensory modalities? To address this question, we tested the sensitivity of blind-from-birth adults to geometrical-invariants using a haptic deviant-figure detection task. Blind participants spontaneously used many geometric concepts such as parallelism, right angles and geometrical shapes to detect intruders in haptic displays, but experienced difficulties with symmetry and complex spatial transformations. Across items, their performance was highly correlated with that of sighted adults performing the same task in touch (blindfolded) and in vision, as well as with the performances of uneducated preschoolers and Amazonian adults. Our results support the existence of an amodal core-system of geometry that arises independently of visual experience. However, performance at selecting geometric intruders was generally higher in the visual compared to the haptic modality, suggesting that sensory-specific spatial experience may play a role in refining the properties of this core-system of geometry.

Effects of Increasing Stimulated Area in Spatiotemporally Congruent Unisensory and Multisensory Conditions

Research has shown that the ability to integrate complementary sensory inputs into a unique and coherent percept based on spatiotemporal coincidence can improve perceptual precision, namely multisensory integration. Despite the extensive research on multisensory integration, very little is known about the principal mechanisms responsible for the spatial interaction of multiple sensory stimuli. Furthermore, it is not clear whether the size of spatialized stimulation can affect unisensory and multisensory perception. The present study aims to unravel whether the stimulated area’s increase has a detrimental or beneficial effect on sensory threshold. Sixteen typical adults were asked to discriminate unimodal (visual, auditory, tactile), bimodal (audio-visual, audio-tactile, visuo-tactile) and trimodal (audio-visual-tactile) stimulation produced by one, two, three or four devices positioned on the forearm. Results related to unisensory conditions indicate that the increase of the stimulated area has a detrimental effect on auditory and tactile accuracy and visual reaction times, suggesting that the size of stimulated areas affects these perceptual stimulations. Concerning multisensory stimulation, our findings indicate that integrating auditory and tactile information improves sensory precision only when the stimulation area is augmented to four devices, suggesting that multisensory interaction is occurring for expanded spatial areas.

The effects of visual impairment on motor imagery in children and adolescents

BACKGROUND

While the development of motor imagery (MI) has been extensively studied in sighted children, it is not clear how children with different severities of visual impairment (VI) represent motor actions by using the motor representations constructed through the remaining intact senses, especially touch.

AIMS

Mental chronometry and generation/manipulation of MI were examined in children with and without VI.

METHODS AND PROCEDURES

Participants included 64 youth with and without VI (33 without visual impairments, 14 moderate-to-severe, and 17 blind). Mental chronometry was assessed with the imagined Timed-Up-and-Go-Test (iTUG), and generation/manipulation of MI with the Controllability-of-Motor-Imagery-Test (CMI). In addition, the effect of working memory performance (Letter-Number-Sequencing) and physical activity upon MI were evaluated.

RESULTS

Mental duration for the iTUG was significantly shorter than the active durations. Results also provided evidence of better haptic representation than motor representation in all participants; however, only for the CMI-regeneration condition controls outperformed children with visual impairments and blindness (CVIB). Exercise and working memory performance showed a significant contribution only on a few MI tests.

CONCLUSION AND IMPLICATIONS

Our results suggest a possible relationship between motor performance, body representation deficits and visual impairment which needs to be addressed in the evaluation and treatment of CVIB. The design of new rehabilitation interventions that focus on strengthening adequate body perception and representation should be proposed and tested to promote motor development in CVIB.

Learning My Way: A Pilot Study of Navigation Skills in Cerebral Palsy in Immersive Virtual Reality

Purpose: Human navigation skills are essential for everyday life and rely on several cognitive abilities, among which visual-spatial competences that are impaired in subjects with cerebral palsy (CP). In this work, we proposed navigation tasks in immersive virtual reality (IVR) to 15 children with CP and 13 typically developing (TD) peers in order to assess the individual navigation strategies and their modifiability in a situation resembling real life. Methods: We developed and adapted to IVR an application based on a 5-way maze in a playground that was to be navigated to find a reward. The learning process, navigation strategies, and adaptation to changes were compared between participants with CP and their TD peers and correlated with visual-spatial abilities and cognitive competences. Results: Most participants with CP needed more attempts than TD participants to become proficient in navigation. Furthermore, the learning phase was correlated to visual-spatial memory but not with cognitive competences. Interestingly, navigation skills were comparable between groups after stabilization. While TD participants mainly relied on allocentric strategies based on environmental cues, egocentric (self-centered) strategies based on body motion prevailed in participants with CP. Furthermore, participants with CP had more difficulties in modifying their navigation strategies, caused by difficulties in executive processes beyond the visual-perceptual impairment, with an inefficient shift between implicit and explicit competences. Conclusions: The navigation abilities in participants with CP seem to be different from their TD peers in terms of learning and adaptation to new conditions; this could deeply affect their everyday life and ultimately participation and inclusion. A regular assessing and focused rehabilitative plans could help to better navigate the environment and affect self-perception.

Standardized and Experimental Tools to Assess Spatial Cognition in Visually Impaired Children: A Mini-Review

The acquisition of spatial cognition is essential for both everyday functioning (e.g., navigation) and more specific goals (e.g., mathematics), therefore being able to assess and monitor spatial cognition from the first years of life would be essential to predict developmental outcomes and timely intervene whenever spatial development is compromised. Several shreds of evidence have indicated that spatial development can be compromised in the case of development with atypical sensory experience such as blindness. Despite the massive importance of spatial abilities for the development of psychomotor competencies across childhood, only a few standardized and experimental methods have been developed to assess them in visually impaired children. In this review, we will give a short overview of current formal (standardized) and informal (experimental) methods to assess spatial cognition in visually impaired children, demonstrating that very few validated tools have been proposed to date. The main contribution of this current work is to highlight the need of ad hoc studies to create and validate clinical measures to assess spatial cognition in visually impaired individuals and address potential future developments in this area of research.

Multisystemic Increment of Cortical Thickness in Congenital Blind Children

It has been shown that the total or partial lack of visual experience is associated with a plastic reorganization at the brain level, more prominent in congenital blind. Cortical thickness (CT) studies, to date involving only adult subjects, showed that only congenital blind have a thicker cortex than age-matched sighted population while late blind do not. This was explained as a deviation from the physiological mechanism of initial neural growth followed by a pruning mechanism that, in congenital blind children, might be reduced by their visual deprivation, thus determining a thicker cortex. Since those studies involved only adults, it is unknown when these changes may appear and whether they are related to impairment degree. To address this question, we compared the CT among 28 children, from 2 to 12 years, with congenital visual impairments of different degree and an age-matched sighted population. Vertex-wise analysis showed that blind children, but not low vision one, had a thicker cortical surface in few clusters located in occipital, superior parietal, anterior-cingular, orbito-frontal, and mesial precentral regions. Our data suggest that the effect of visual impairment on determining thicker cortex is an early phenomenon, is multisystemic, and occurs only when blindness is almost complete.

Navigation aid for blind persons by visual-to-auditory sensory substitution: A pilot study

PURPOSE

In this study, we investigate to what degree augmented reality technology can be used to create and evaluate a visual-to-auditory sensory substitution device to improve the performance of blind persons in navigation and recognition tasks.

METHODS

A sensory substitution algorithm that translates 3D visual information into audio feedback was designed. This algorithm was integrated in an augmented reality based mobile phone application. Using the mobile device as sensory substitution device, a study with blind participants (n = 7) was performed. The participants navigated through pseudo-randomized obstacle courses using either the sensory substitution device, a white cane or a combination of both. In a second task, virtual 3D objects and structures had to be identified by the participants using the same sensory substitution device.

RESULTS

The realized application for mobile devices enabled participants to complete the navigation and object recognition tasks in an experimental environment already within the first trials without previous training. This demonstrates the general feasibility and low entry barrier of the designed sensory substitution algorithm. In direct comparison to the white cane, within the study duration of ten hours the sensory substitution device did not offer a statistically significant improvement in navigation.

A Multidimensional, Multisensory and Comprehensive Rehabilitation Intervention to Improve Spatial Functioning in the Visually Impaired Child: A Community Case Study

Congenital visual impairment may have a negative impact on spatial abilities and result in severe delays in perceptual, social, motor, and cognitive skills across life span. Despite several evidences have highlighted the need for an early introduction of re-habilitation interventions, such interventions are rarely adapted to children’s visual capabilities and very few studies have been conducted to assess their long-term efficacy. In this work, we present a case study of a visually impaired child enrolled in a newly developed re-habilitation intervention aimed at improving the overall development through the diversification of re-habilitation activities based on visual potential and developmental profile, with a focus on spatial functioning. We argue that intervention for visually impaired children should be (a) adapted to their visual capabilities, in order to increase re-habilitation outcomes, (b) multi-interdisciplinary and multidimensional, to improve adaptive abilities across development, (c) multisensory, to promote the integration of different perceptual information coming from the environment.

Spatial Competence and Brain Plasticity in Congenital Blindness via Sensory Substitution Devices

In congenital blindness (CB), tactile, and auditory information can be reinterpreted by the brain to compensate for visual information through mechanisms of brain plasticity triggered by training. Visual deprivation does not cause a cognitive spatial deficit since blind people are able to acquire spatial knowledge about the environment. However, this spatial competence takes longer to achieve but is eventually reached through training-induced plasticity. Congenitally blind individuals can further improve their spatial skills with the extensive use of sensory substitution devices (SSDs), either visual-to-tactile or visual-to-auditory. Using a combination of functional and anatomical neuroimaging techniques, our recent work has demonstrated the impact of spatial training with both visual to tactile and visual to auditory SSDs on brain plasticity, cortical processing, and the achievement of certain forms of spatial competence. The comparison of performances between CB and sighted people using several different sensory substitution devices in perceptual and sensory-motor tasks uncovered the striking ability of the brain to rewire itself during perceptual learning and to interpret novel sensory information even during adulthood. We discuss here the implications of these findings for helping blind people in navigation tasks and to increase their accessibility to both real and virtual environments.

Efficiency of Sensory Substitution Devices Alone and in Combination With Self-Motion for Spatial Navigation in Sighted and Visually Impaired

Human adults can optimally combine vision with self-motion to facilitate navigation. In the absence of visual input (e.g., dark environments and visual impairments), sensory substitution devices (SSDs), such as The vOICe or BrainPort, which translate visual information into auditory or tactile information, could be used to increase navigation precision when integrated together or with self-motion. In Experiment 1, we compared and assessed together The vOICe and BrainPort in aerial maps task performed by a group of sighted participants. In Experiment 2, we examined whether sighted individuals and a group of visually impaired (VI) individuals could benefit from using The vOICe, with and without self-motion, to accurately navigate a three-dimensional (3D) environment. In both studies, 3D motion tracking data were used to determine the level of precision with which participants performed two different tasks (an egocentric and an allocentric task) and three different conditions (two unisensory conditions and one multisensory condition). In Experiment 1, we found no benefit of using the devices together. In Experiment 2, the sighted performance during The vOICe was almost as good as that for self-motion despite a short training period, although we found no benefit (reduction in variability) of using The vOICe and self-motion in combination compared to the two in isolation. In contrast, the group of VI participants did benefit from combining The vOICe and self-motion despite the low number of trials. Finally, while both groups became more accurate in their use of The vOICe with increased trials, only the VI group showed an increased level of accuracy in the combined condition. Our findings highlight how exploiting non-visual multisensory integration to develop new assistive technologies could be key to help blind and VI persons, especially due to their difficulty in attaining allocentric information.

The Impact of Vision Loss on Allocentric Spatial Coding

Several works have demonstrated that visual experience plays a critical role in the development of allocentric spatial coding. Indeed, while children with a typical development start to code space by relying on allocentric landmarks from the first year of life, blind children remain anchored to an egocentric perspective until late adolescence. Nonetheless, little is known about when and how visually impaired children acquire the ability to switch from an egocentric to an allocentric frame of reference across childhood. This work aims to investigate whether visual experience is necessary to shift from bodily to external frames of reference. Children with visual impairment and normally sighted controls between 4 and 9 years of age were asked to solve a visual switching-perspective task requiring them to assume an egocentric or an allocentric perspective depending on the task condition. We hypothesize that, if visual experience is necessary for allocentric spatial coding, then visually impaired children would have been impaired to switch from egocentric to allocentric perspectives. Results support this hypothesis, confirming a developmental delay in the ability to update spatial coordinates in visually impaired children. It suggests a pivotal role of vision in shaping allocentric spatial coding across development.

Spotlights and Soundscapes

For persons with visual impairment, forming cognitive maps of unfamiliar interior spaces can be challenging. Various technical developments have converged to make it feasible, without specialized equipment, to represent a variety of useful landmark objects via spatial audio, rather than solely dispensing route information. Although such systems could be key to facilitating cognitive map formation, high-density auditory environments must be crafted carefully to avoid overloading the listener. This article recounts a set of research exercises with potential users, in which the optimization of such systems was explored. In Experiment 1, a virtual reality environment was used to rapidly prototype and adjust the auditory environment in response to participant comments. In Experiment 2, three variants of the system were evaluated in terms of their effectiveness in a real-world building. This methodology revealed a variety of optimization approaches and recommendations for designing dense mixed-reality auditory environments aimed at supporting cognitive map formation by visually impaired persons.

Objective and Perceived Neighborhood Greenness of Students Differ in their Agreement in Home and Study Environments

Research has reported the associations between objective or subjective neighborhood greenness and health, with low agreement between the greenness scores. College students are prone to poor health, and data are lacking on home and university environments. We studied the agreement between greenness parameters and the associations of objective greenness with health in different locations. Three hundred and seventy-seven college students were recruited, with a mean age of 24 years, in the city of Graz, Austria. Objective and perceived greenness was assessed at home and at university. Health measures included the WHO-5 questionnaire for mental health, the IPAQ questionnaire (short) for physical activity and sedentariness, and body mass index. Per location, quintile pairs of objective and perceived greenness were classified into underestimates, correct estimates or overestimates. Interrater reliability and correlation analyses revealed agreement between greenness scores at home but not at university. ANOVA models only showed poorer mental health for students underestimating greenness at university (M = 51.38, SD = 2.84) compared to those with correct estimates (M = 61.03, SD = 1.85). Agreement between greenness scores at home but not at university was obtained, and mental health was related to the perception of greenness at university. We conclude that reliable and corresponding methods for greenness scores need to be developed.

Audio-Motor Training Enhances Auditory and Proprioceptive Functions in the Blind Adult

Several reports indicate that spatial perception in blind individuals can be impaired as the lack of visual experience severely affects the development of multisensory spatial correspondences. Despite the growing interest in the development of technological devices to support blind people in their daily lives, very few studies have assessed the benefit of interventions that help to refine sensorimotor perception. In the present study, we directly investigated the impact of a short audio-motor training on auditory and proprioceptive spatial perception in blind individuals. Our findings indicate that auditory and proprioceptive spatial capabilities can be enhanced through interventions designed to foster sensorimotor perception in the form of audio-motor correspondences, demonstrating the importance of the early introduction of sensorimotor training in therapeutic intervention for blind individuals.

Adults' spatial scaling: evidence from the haptic domain

The current study investigated adults' spatial-scaling abilities using a haptic localization task. As a first aim, we examined the strategies used to solve this haptic task. Secondly, we explored whether irrelevant visual information influenced adults' spatial-scaling performance. Thirty-two adults were asked to locate targets as presented in maps on a larger or same-sized referent space. Maps varied in size in accordance with different scaling factors (1:4, 1:2, 1:1), whereas the referent space was constant in size throughout the experimental session. The availability of irrelevant, non-informative vision was manipulated by blindfolding half of the participants prior to the experiment (condition without non-informative vision), whereas the other half were able to see their surroundings with the stimuli being hidden behind a curtain (condition with non-informative vision). Analyses with absolute errors (after correcting for reversal errors) as the dependent variable revealed a significant interaction of the scaling factor and non-informative vision condition. Adults in the blindfolded condition showed constant errors and response times irrespective of scaling factor. Such a response pattern indicates the usage of relative strategies. Adults in the curtain condition showed a linear increase in errors with higher scaling factors, whereas their response times remained constant. This pattern of results supports the usage of absolute strategies or mental transformation strategies. Overall, our results indicate different scaling strategies depending on the availability of non-informative vision, highlighting the strong influence of (even irrelevant) vision on adults' haptic processing.

Blindness, Psychosis, and the Visual Construction of the World

The relationship between visual loss and psychosis is complex: congenital visual loss appears to be protective against the development of a psychotic disorder, particularly schizophrenia. In later life, however, visual deprivation or visual loss can give rise to hallucinosis, disorders of visual insight such as blindsight or Anton syndrome, or, in the context of neurodegenerative disorders, more complex psychotic presentations. We draw on a computational psychiatric approach to consider the foundational role of vision in the construction of representations of the world and the effects of visual loss at different developmental stages. Using a Bayesian prediction error minimization model, we describe how congenital visual loss may be protective against the development of the kind of computational deficits postulated to underlie schizophrenia, by increasing the precision (and consequent stability) of higher-level (including supramodal) priors, focusing on visual loss-induced changes in NMDA receptor structure and function as a possible mechanistic substrate. In simple terms, we argue that when people cannot see from birth, they rely more heavily on the context they extract from the other senses, and the resulting model of the world is more impervious to the false inferences, made in the face of inevitably noisy perceptual input, that characterize schizophrenia. We show how a Bayesian prediction error minimization framework can also explain the relationship between later visual loss and other psychotic symptoms, as well as the effects of visual deprivation and hallucinogenic drugs, and outline experimentally testable hypotheses generated by this approach.

How Much Spatial Information Is Lost in the Sensory Substitution Process? Comparing Visual, Tactile, and Auditory Approaches

Sensory substitution devices (SSDs) can convey visuospatial information through spatialised auditory or tactile stimulation using wearable technology. However, the level of information loss associated with this transformation is unknown. In this study, novice users discriminated the location of two objects at 1.2 m using devices that transformed a 16 × 8-depth map into spatially distributed patterns of light, sound, or touch on the abdomen. Results showed that through active sensing, participants could discriminate the vertical position of objects to a visual angle of 1°, 14°, and 21°, and their distance to 2 cm, 8 cm, and 29 cm using these visual, auditory, and haptic SSDs, respectively. Visual SSDs significantly outperformed auditory and tactile SSDs on vertical localisation, whereas for depth perception, all devices significantly differed from one another (visual > auditory > haptic). Our findings highlight the high level of acuity possible for SSDs even with low spatial resolutions (e.g., 16 × 8) and quantify the level of information loss attributable to this transformation for the SSD user. Finally, we discuss ways of closing this “modality gap” found in SSDs and conclude that this process is best benchmarked against performance with SSDs that return to their primary modality (e.g., visuospatial into visual).

The Role of Visual Experience in Auditory Space Perception around the Legs

It is widely accepted that vision plays a key role in the development of spatial skills of the other senses. Recent works have shown that blindness is often associated with auditory spatial deficits. The majority of previous studies have focused on understanding the representation of the upper frontal body space where vision and actions have a central role in mapping the space, however less research has investigated the back space and the space around the legs. Here we investigate space perception around the legs and the role of previous visual experience, by studying sighted and blind participants in an audio localization task (front-back discrimination). Participants judged if a sound was delivered in their frontal or back space. The results showed that blindfolded sighted participants were more accurate than blind participants in the frontal space. However, both groups were similarly accurate when auditory information was delivered in the back space. Blind individuals performed the task with similar accuracy for sounds delivered in the frontal and back space, while sighted people performed better in the frontal space. These results suggest that visual experience influences auditory spatial representations around the legs. Moreover, these results suggest that hearing and vision play different roles in different spaces.

Test-retest reliability of BSP, a battery of tests for assessing spatial cognition in visually impaired children

Blind individuals are particularly dependent on their hearing for defining space. It has been found that both children and adults with visual impairments can struggle with complex spatial tasks that require a metric representation of space. Nonetheless the variability of methods employed to assess spatial abilities in absence of vision is wide, especially in the case of visually impaired children. For this reason, it would be necessary to define a battery of tests that appropriately assess different aspects of spatial perception and to investigate its reliability in order to provide a standard assessment of spatial abilities not only in experimental but also in clinical settings. The aim of this study is to determine the test–retest reliability of a battery of six spatial tasks (BSP, Blind Spatial Perception) and provide the first gold standard for assessing spatial cognition deficits in visually impaired children. Thirty visually impaired children aged 6–17 participated in two identical sessions, at a distance of 10 weeks, in which they performed six spatial tasks: auditory bisection, auditory localization, auditory distance discrimination, auditory reaching, proprioceptive reaching, and general mobility. Test–retest reliability was assessed using the test-retest scatter plots, intra-class correlation coefficient (ICC), and coefficient of variation (CV). The results showed good-to-excellent reliability for all six tests, with average ICC values ranging from 0.77 to 0.89 and average CV values ranging from 3.44% to 15.27%. In conclusion, the newly proposed battery (BSP) results as a reliable tool to identify spatial impairments in visually impaired children.

Improving spatial working memory in blind and sighted youngsters using programmable tactile displays

OBJECTIVE

To investigate whether training with tactile matrices displayed with a programmable tactile display improves recalling performance of spatial images in blind, low-vision and sighted youngsters. To code and understand the behavioral underpinnings of learning two-dimensional tactile dispositions, in terms of spontaneous exploration strategies.

METHODS

Three groups of blind, low-vision and sighted youngsters between 6 and 18 years old performed four training sessions with a weekly schedule in which they were asked to memorize single or double spatial layouts, featured as two-dimensional matrices.

RESULTS

Results showed that all groups of participants significantly improved their recall performance compared to the first session baseline in the single-matrix task. No statistical difference in performance between groups emerged in this task. Instead, the learning effect in visually impaired participants is reduced in the double-matrix task, whereas it is still robust in blindfolded sighted controls. We also coded tactile exploration strategies in both tasks and their correlation with performance. Sighted youngsters, in particular, favored a proprioceptive exploration strategy. Finally, performance in the double-matrix task negatively correlated with using one hand and positively correlated with a proprioceptive strategy.

CONCLUSION

The results of our study indicate that blind persons do not easily process two separate spatial layouts. However, rehabilitation programs promoting bi-manual and proprioceptive approaches to tactile exploration might help improve spatial abilities. Finally, programmable tactile displays are an effective way to make spatial and graphical configurations accessible to visually impaired youngsters and they can be profitably exploited in rehabilitation.