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.

Environmental Information Required by Individuals with Visual Impairments Who Use Orientation and Mobility Aids to Navigate Campuses

Introduction:

This study investigated the user requirements of individuals with visual impairments regarding the information to be included in orientation and mobility (O&M) aids in order for optimally useful audio-tactile maps of campuses to be developed. In addition, this study aimed at investigating the importance (usefulness) that individuals with visual impairments attribute to environmental information of campuses.

Methods:

The researchers listed 213 pieces of environmental information concerning campuses and address them in survey by conducting a respective questionnaire. Participants were asked to evaluate the information, regarding the importance or usefulness of the information in regard to safety, location of services, and orientation and wayfinding during movement. Through convenience sampling 115 adults (aged from 18 to 64 years) with visual impairments from four countries (Greece, Cyprus, Turkey, and Germany) took part in the research.

Results:

Pieces of environmental information, sorted in descending order starting with the most useful ones, have been listed. A repeated measures analysis of variance yielded a significant main effect for the type of information (safety, location of services, and wayfinding and orientation): F(2, 228) = 70.868, p < .001.

Discussion:

This study resulted in the specification of the most significant or useful information that should be included in O&M aids of campuses for individuals with visual impairments.

Implications for practitioners:

The results of this study will hold the interest of developers of O&M aids, O&M practitioners, rehabilitation teachers, and instructors who design and construct O&M aids. Moreover, the context for appropriately designed tactile or audio-tactile maps for campuses is provided, and campuses around the world could rely on this study for the creation of a valuable accessibility aid.

Cognitive Mapping Without Vision: Comparing Wayfinding Performance After Learning From Digital Touchscreen-Based Multimodal Maps vs. Embossed Tactile Overlays

This article starts by discussing the state of the art in accessible interactive maps for use by blind and visually impaired (BVI) people. It then describes a behavioral experiment investigating the efficacy of a new type of low-cost, touchscreen-based multimodal interface, called a vibro-audio map (VAM), for supporting environmental learning, cognitive map development, and wayfinding behavior on the basis of nonvisual sensing. In the study, eight BVI participants learned two floor-maps of university buildings, one using the VAM and the other using an analogous hardcopy tactile map (HTM) overlaid on the touchscreen. They were asked to freely explore each map, with the task of learning the entire layout and finding three hidden target locations. After meeting a learning criterion, participants performed an environmental transfer test, where they were brought to the corresponding physical layout and were asked to plan/navigate routes between learned target locations from memory, i.e., without access to the map used at learning. The results using Bayesian analyses aimed at assessing equivalence showed highly similar target localization accuracy and route efficiency performance between conditions, suggesting that the VAM supports the same level of environmental learning, cognitive map development, and wayfinding performance as is possible from interactive displays using traditional tactile map overlays. These results demonstrate the efficacy of the VAM for supporting complex spatial tasks without vision using a commercially available, low-cost interface and open the door to a new era of mobile interactive maps for spatial learning and wayfinding by BVI navigators.

Enhancing general spatial skills of young visually impaired people with a programmable distance discrimination training: a case control study

BACKGROUND

The estimation of relative distance is a perceptual task used extensively in everyday life. This important skill suffers from biases that may be more pronounced when estimation is based on haptics. This is especially true for the blind and visually impaired, for which haptic estimation of distances is paramount but not systematically trained. We investigated whether a programmable tactile display, used autonomously, can improve distance discrimination ability in blind and severely visually impaired youngsters between 7 and 22 years-old.

METHODS

Training consisted of four weekly sessions in which participants were asked to haptically find, on the programmable tactile display, the pairs of squares which were separated by the shortest and longest distance in tactile images with multiple squares. A battery of haptic tests with raised-line drawings was administered before and after training, and scores were compared to those of a control group that did only the haptic battery, without doing the distance discrimination training on the tactile display.

RESULTS

Both blind and severely impaired youngsters became more accurate and faster at the task during training. In haptic battery results, blind and severely impaired youngsters who used the programmable display improved in three and two tests, respectively. In contrast, in the control groups, the blind control group improved in only one test, and the severely visually impaired in no tests.

CONCLUSIONS

Distance discrimination skills can be trained equally well in both blind and severely impaired participants. More importantly, autonomous training with the programmable tactile display had generalized effects beyond the trained task. Participants improved not only in the size discrimination test but also in memory span tests. Our study shows that tactile stimulation training that requires minimal human assistance can effectively improve generic spatial skills.

The Target-Route Map: Evaluating Its Usability for Visually Impaired Persons

Two experiments demonstrated the usability of the target-route map in locating and identifying unfamiliar routes by persons who are visually impaired. Compared to the orientation map and the mobility map of the same area, the target-route map was read faster, and more of its details were recalled correctly.

British Antidiscrimination Legislation and Wayfinding in Buildings in Scotland

This article presents the results of a study of the impact of the Disability Discrimination Act (DDA) 1995 on the provision of wayfinding aids in local authority buildings in Scotland. The study found that although the DDA has raised awareness in local authorities of the needs of disabled users of buildings, it has not necessarily led to the incorporation of wayfinding aids in new or refurbished buildings.

Interventions to improve functioning, participation, and quality of life in children with visual impairment: a systematic review

Visual impairment in childhood often has life-long implications. To aim for the highest levels of functioning, participation, and quality of life and to ensure children's well-being, children should be entitled to the most effective rehabilitation programs. We review evidence for the effectiveness of rehabilitation interventions for children with visual impairment to improve skills and behavior, thereby improving participation and quality of life as an ultimate goal. Of the 441 potentially relevant articles identified, 66 studies met our inclusion criteria (i.e., 28 randomized controlled trials, 18 nonrandomized controlled trials, and 20 before-after comparisons). The results suggest that sports camps, prescription and training in the use of low vision devices, and oral hygiene programs might be effective in improving functioning and elements of participation and quality of life in children with visual impairment. Other interventions showed mixed or negative results. The results should be interpreted with caution because of moderate to high risk of bias and suboptimal reporting. Heterogeneity of results and the use of over 50 different outcome measures prevented a meta-analysis. Future studies should focus on promising interventions for which effectiveness is still unclear (e.g., mobility, social skills), with adequately designed methodology.

Updated Tactile Feedback with a Pin Array Matrix Helps Blind People to Reduce Self-Location Errors

Autonomous navigation in novel environments still represents a challenge for people with visual impairment (VI). Pin array matrices (PAM) are an effective way to display spatial information to VI people in educative/rehabilitative contexts, as they provide high flexibility and versatility. Here, we tested the effectiveness of a PAM in VI participants in an orientation and mobility task. They haptically explored a map showing a scaled representation of a real room on the PAM. The map further included a symbol indicating a virtual target position. Then, participants entered the room and attempted to reach the target three times. While a control group only reviewed the same, unchanged map on the PAM between trials, an experimental group also received an updated map representing, in addition, the position they previously reached in the room. The experimental group significantly improved across trials by having both reduced self-location errors and reduced completion time, unlike the control group. We found that learning spatial layouts through updated tactile feedback on programmable displays outperforms conventional procedures on static tactile maps. This could represent a powerful tool for navigation, both in rehabilitation and everyday life contexts, improving spatial abilities and promoting independent living for VI people.

How do people remember spatial information from tactile maps?

This study investigates the strategies people use spontaneously to remember spatial information from touch and movement to understand why tactile maps are often found difficult. We compared task-filled with unfilled delays in location and distance tasks. Locations showed highly significant effects of the longer, more complex positioning movements used here in location recall, but no interference from the interpolated tasks, except marginally from counting backwards. By contrast, recall by the same participants of a repeated small distance showed highly significant interference from interpolated spatial rotation and movements. Speech suppression had no effects. The findings suggest that spontaneous spatial heuristics vary with the ease and consistency of positioning movements in recall, and cannot be inferred from type (location or distance) of spatial task. The discussion considers the practical implications of the findings.

Spatial navigation by congenitally blind individuals

Spatial navigation in the absence of vision has been investigated from a variety of perspectives and disciplines. These different approaches have progressed our understanding of spatial knowledge acquisition by blind individuals, including their abilities, strategies, and corresponding mental representations. In this review, we propose a framework for investigating differences in spatial knowledge acquisition by blind and sighted people consisting of three longitudinal models (i.e., convergent, cumulative, and persistent). Recent advances in neuroscience and technological devices have provided novel insights into the different neural mechanisms underlying spatial navigation by blind and sighted people and the potential for functional reorganization. Despite these advances, there is still a lack of consensus regarding the extent to which locomotion and wayfinding depend on amodal spatial representations. This challenge largely stems from methodological limitations such as heterogeneity in the blind population and terminological ambiguity related to the concept of cognitive maps. Coupled with an over‐reliance on potential technological solutions, the field has diffused into theoretical and applied branches that do not always communicate. Here, we review research on navigation by congenitally blind individuals with an emphasis on behavioral and neuroscientific evidence, as well as the potential of technological assistance. Throughout the article, we emphasize the need to disentangle strategy choice and performance when discussing the navigation abilities of the blind population. WIREs Cogn Sci 2016, 7:37–58. doi: 10.1002/wcs.1375

For further resources related to this article, please visit the WIREs website.

Self-motion direction discrimination in the visually impaired

Despite the close interrelation between vestibular and visual processing (e.g., vestibulo-ocular reflex), surprisingly little is known about vestibular function in visually impaired people. In this study, we investigated thresholds of passive whole-body motion discrimination (leftward vs. rightward) in nine visually impaired participants and nine age-matched sighted controls. Participants were rotated in yaw, tilted in roll, and translated along the interaural axis at two different frequencies (0.33 and 2 Hz) by means of a motion platform. Superior performance of visually impaired participants was found in the 0.33 Hz roll tilt condition. No differences were observed in the other motion conditions. Roll tilts stimulate the semicircular canals and otoliths simultaneously. The results could thus reflect a specific improvement in canal-otolith integration in the visually impaired and are consistent with the compensatory hypothesis, which implies that the visually impaired are able to compensate the absence of visual input.

Encoding modality and spatial memory retrieval

This study examined the temporal characteristics of event-related brain electrical activity associated with the processing of spatial memories derived from linguistic and tactile information. Participants learned a map by (1) reading a text description of the map, (2) touching a wooden topological representation of the map (hidden from view), or (3) both. Subsequently, the participants' ability to use their spatial knowledge was tested in a spatial orientation task. Differential patterns of brain activity as a function of encoding modality were found at the very early (preconscious) stages of processing. In contrast, an analysis of behavioral performance revealed no differences between the encoding groups. A model of spatial memory retrieval is presented to account for the findings.