Blindness and Brain Plasticity in Navigation and Object Perception


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INTRODUCTION

All of these groups do research in this area but generally do not collaborate with one another. This book is an attempt to bring together the disparate threads of research into a single volume, appropriate for all three markets.

John J. Rieser , Anne L. Continue these comparisons in touch adaptation by trying stimuli of different sizes and weights and on different regions of both sides of your hand. Compare touch adaptation in both locations and notice the general phenomenon of touch adaptation. Photo by R. Link - You can see a demonstration of the rubber hand illusion on YouTube. First assemble 10 miscellaneous objects of similar sizes that you find in your room. Place them on your desk and close your eyes.

Identify an object by exploring it with active touch. Pay attention to how you move your fingers around an object to determine its identity. Next determine the hardness of your desktop and other nearby objects. Do you use your hands differently than you did when identifying objects?

Finally, use your fingers to determine the texture of your shirt and other objects. You should again notice that your fingers move in a different fashion to perform this task. Link - International Society for Haptics. Find a metal fork or spoon. Touch the bottom of the handle to your forehead, chest, stomach, shoulder, arm, foot, and calf. Notice that the handle feels cold when you touch some parts of your body, but its temperature is not noticeable on other body parts.

Now run hot water on the utensil handle, wipe it off quickly, and touch it to your forehead. Repeat this process for each body part where you tested the spoon originally. Where is the heat most noticeable? To test for temperature thresholds with cold stimuli, place a bunch of pennies in a freezer for a couple of hours.

Touch the pennies to the same body parts you have been testing. Where is the cold most noticeable? Fill one with very hot tap water but not so hot that it is painful , another with very cold tap water, and a third with a mixture of water from the other two bowls this will give you lukewarm water. Arrange the three bowls so that the cold water is on your right, the hot water is on your left, and the lukewarm water is in the middle. Place your right hand in the cold water and your left hand in the hot water. Leave your hands in these bowls for approximately 3 minutes and then quickly transfer both hands to the lukewarm middle bowl.

Notice the apparent temperature of each hand. You can also watch a documentary on children with congenital insensitivity to pain. Darling Bioledical Library. Kinesthetic and Vestibular Senses. First, set up the two chairs, one behind the other. Now, sit in the first chair, and have your friend sit in the chair right in front of you. Close your eyes and have your friend take your dominant hand and place it on their nose.

Here comes the weird part. Put your other hand on your own nose. Imitate these movements on your own nose. Try to make the movements synchronize as best as possible. Continue this for thirty seconds to a minute. 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. 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.

Blindness and Brain Plasticity in Navigation and Object Perception | Taylor & Francis Group

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.

For further resources related to this article, please visit the WIREs website. Blind individuals are faced with the challenge of finding their way through built environments that can be difficult to interpret, disorienting, and even intimidating. Despite the impressive number of technological advances for reviews, see Refs 3 , 4 , 5 , these devices are not often used by the blind population. This confusion has led to apparently contradictory results that have propagated through the field and, consequently, a lack of clarity regarding the navigation abilities of blind people.

We approach the topic from the perspective that blind and sighted people may have similar potential i. Our position is that, in order to investigate the abilities of blind individuals, researchers should study the relationship between navigation strategies i. For example, this occurs when sighted participants are asked to wear blindfolds or when blind participants are asked to complete visually guided tasks e.

In such cases, a difference in performance is inconclusive with respect to abilities alone because the strategy adopted by both blind and sighted people invariably disadvantages one of the groups. These results are also inconclusive when researchers are unable to detect a difference in performance. Indeed, a nonsignificant difference does not necessarily provide evidence for the absence of an effect. In contrast, allowing participants to adopt different strategies would provide insight into the abilities of blind and sighted people. Four possible outcomes of studying the interaction between spatial strategies and performances in spatial tasks.

In order to provide a comprehensive review on navigation and blindness, we limit ourselves to research on congenitally blind individuals. Previous research often separates the congenitally blind people from the adventitiously blind, blindfolded sighted, and sighted people.

Comparisons across these groups are appropriate but difficult to implement because of lack of agreement regarding the distinction between congenitally and adventitiously blind individuals in terms of acuity, age of onset, and the presence or absence of additional disabilities. Moreover, comparisons between blind and sighted groups can be problematic if the task inherently favors the visual modality.

This review is organized into six sections. First, we present behavioral research in human spatial navigation. Here, we discuss the concepts of locomotion and wayfinding, different frames of reference e. Second, we discuss discrete and continuous frameworks for the acquisition of spatial knowledge. Third, we contrast different theories regarding the spatial abilities of blind people i. Fourth, we discuss multimodal processing i. Sixth, we consider the future of research in navigation by blind people including a review of technological advances and heterogeneity in the blind population.

At the end of this review, we intend to provide a framework for the interpretation of prior work and the facilitation of future work. Everyday, blind individuals navigate indoor and outdoor environments that favor the visual sense. In order to reach a destination, they must plan and execute a series of decisions through these environments.

These immediate responses are invariably egocentric because environmental information is acquired with reference to the observer's body. In wayfinding, egocentric and allocentric reference frames always involve at least one observer, two environmental features, and the spatial relations among them. There is a tendency to associate blindness with egocentrism, 30 especially at larger scales, 31 but researchers have yet to disentangle whether or not egocentrism in the blind has resulted from aspects of experimental design. Both egocentric and allocentric references frames can be used to represent spaces of different scales.

While several frameworks have been proposed, 22 , 32 we will use the typology described by Schinazi 16 specifically developed for the classification of experiments with blind and visually impaired individuals. Similarly, scale of space influences choice of navigation strategy. Many experiments in the visual impairment and navigation literature involve either learning or testing in a microscale space.

In some cases, participants are asked to learn a microscale environment from which macroscale behaviors can be inferred. On the other hand, microscale investigations provide a new level of explanation for macroscale behavior using neuroscientific evidence. For example, activation of the occipital lobe during tactile tasks have revealed similarities in the neural processes of blind people doing a tactile task and sighted people doing the same task visually. Indeed, the systematic variation afforded by virtual reality may allow researchers to decompose different stages of navigation at the macroscale.

Together, these considerations suggest that learning and testing at the microscale is necessary for navigation research with blind people, but researchers should be cautious when interpreting their results. At the macroscale, researchers have proposed two frameworks for describing the acquisition of spatial knowledge. Along with Golledge 59 and Shemyakin, 60 Siegel and White's 7 framework was influenced by Piaget and Inhelder's 61 stage theory of cognitive development. First, the strict separation of landmark, route, and survey stages is criticized because people are capable of acquiring different types of spatial information in parallel.

Similarly, Ishikawa and Montello 65 found large individual differences with respect to the timing of survey knowledge acquisition. Second, Euclidean spatial knowledge is formed earlier in spatial learning than the discrete framework would suggest.

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These theories posit that the reliability of spatial cues in the environment help determine the extent to which the corresponding information is acquired. Similarly, the Convergent Active Processing in Interrelated Networks CAPIN theory has described the relative weighting of spatial information obtained through different perceptual modalities. Developed from studies with blind and sighted children, this model posits that, in the absence of vision, other modalities receive greater weight than they otherwise would have. Redundancy in the information received through the different specialized modalities allows individuals to compensate for lack of vision.

During wayfinding, some of the information provided by vision, audition, and proprioception is redundant. Compared to the other modalities, vision provides relatively precise information regarding the location of specific features for allocentric encoding. As such, sighted individuals may attribute more weight to vision than to the other modalities.

When sighted individuals are blindfolded, these weights will remain the same. Consequently, blindfolded sighted people may underperform relative to blind people, even for tasks that require allocentric encoding. The effectiveness of auditory information is limited because not all meaningful features emit sounds, and the effectiveness of proprioceptive information may be limited because of physical barriers. However, the combination of audition and proprioception may facilitate the formation of an allocentric reference frame but at a different time scale e.

Assuming redundancy in the spatial information provided by different modalities, the CAPIN theory would predict the amount of spatial knowledge acquired by blind and sighted individuals to eventually converge with experience.


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These models represent extensions of the difference, deficiency, and inefficiency theories proposed by Fletcher 17 that characterizes the history of research on the spatial abilities of blind people. Note that these models assume that vision provides sighted individuals with an initial advantage relative to blind individuals, but there have been a few cases in which the blind outperformed the sighted. For a review of differences in memory and inferential tasks, see Ref 75 , and for a review of methods in spatial cognition and blindness, see Ref Three models of differences in spatial knowledge acquisition between blind and sighted individuals.

Here, experience may refer to exposure to a particular environment, the repeated performance of a particular task, or the general development of spatial ability with age. This model is supported by several lines of research on tactile discrimination, 77 tactile matching, 78 assembly, 73 rotation tasks, 73 and distance estimation 73 , 79 at the microscale. Hollins and Kelley 80 also found that blind and sighted participants performed similarly in a spatial memory task i. In addition, Corazzini and colleagues. However, these results are difficult to interpret because performance in egocentric and allocentric conditions differed on the first trial before learning could have occurred.

At the macroscale, research has shown that, although blind participants tend to plan routes in more detail compared to sighted participants 88 , the accuracy with which models of environments were reconstructed was similar for blind and sighted groups. At its extreme, this model holds that, in the absence of vision, individuals are incapable of forming spatial representations.

There is little evidence to support this view. For example, Cleaves and Royal 91 found that, for both memory and inferential tasks at the microscale, the disparity in performance between blind and sighted individuals increased with task complexity i. This disparity between blind and sighted children increased with the size of the environment under consideration. Worchel 93 provided initial support for this theory using tasks that involves the reproduction and mental matching of geometric forms at the microscale and is often cited as evidence for inefficiency theory because the tasks favored the visual modality.

However, upon careful examination, the results are more in line with the cumulative model given the superior performance of sighted participants and the significant relationship between age of onset and accuracy on spatial tasks. Consequently, this approach cannot distinguish between the three aforementioned longitudinal models. As a result, the number of studies supporting this theory may be overestimated.

For the most part, these patterns in performance are also present at the macroscale. Here, blind participants exhibited difficulties in terms of inferential direction tasks, direction estimation from memory, distance estimation, model construction, 44 , and sketch maps. Interestingly, there is less support for the persistent model than the convergent or cumulative models in the developmental literature for a review, see Refs 14 , Others have suggested that the natural course of development may eliminate performance gaps in terms of sensorimotor understanding and exploration of the environment.

The spatial representations underlying navigation performance can be abstracted from different perceptual modalities. Disadvantages of the blind during navigation have been attributed to this distinction between vision and the other modalities. However, the extent to which the information acquired by any modality is sequential or simultaneous depends on the spatial and temporal scales under consideration. As such, all of the perceptual modalities are sequential and simultaneous to some extent. Visual information, for example is distributed along time as well as space.

The eyes tend to fixate one object at a time as they survey a scene, and larger scenes require the integration of visual information over a longer period of time. The advantage of vision is thus the speed with which the eyes can move compared to head or body movements. While sensory substitution devices SSDs have improved the spatial and temporal resolution of available spatial information e.

Amodality posits that spatial representations can be abstracted from the perceptual modality through which the information was originally acquired. First, several researchers have attributed similarities in the performance of blind and sighted individuals i. Here, functional equivalence refers to similarities in performance resulting from information gained through two or more perceptual modalities or language , Despite these efforts, amodality remains an open issue in the literature because of the difficulty in disentangling representation and process using behavioral data.

These two sets of parameters can be used in order to calculate the optimal localization response according to the Bayesian model from trial to trial. On the one hand, significant deviations from this optimal response would indicate evidence against amodality. Such deviations may result from either a failure to integrate the two cues or a disparity between the objective cues and the perceived cues. This disparity may be used in order to match cues from different modalities e. At the same time, this possibility can be eliminated by also obtaining responses to the two cues individually as recommended by Cheng et al.

On the other hand, the extent to which the Bayesian model can predict localization responses would indicate evidence towards amodality. In the introduction to The Hippocampus as a Cognitive Map , O'Keefe and Nadel later revised this reference to Tolman by acknowledging that the original definition of cognitive map was too vague for their purposes. According to their new definition, cognitive maps were psychological spaces with absolute reference frames. The current challenge with cognitive maps stems from the vague definitions of the term, its constant reformulation, , and inaccurate citations of Tolman's and O'Keefe's previous work.

At its most extreme, cognitive maps are considered structurally analogous to a cartographic map in that they represent Euclidean spatial relations in a global format, from a top—down view, and with an allocentric frame of reference.

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Cognitive maps may be defined with respect to level of abstraction e. Consequently, different researchers have employed different tasks in order to investigate cognitive maps. For example, reference frames can include a perspective, but a perspective does not necessarily assume a particular reference frame. With respect to research on the blind population, the term cognitive map continues to be loosely applied.

There are many important findings regarding the content i. However, separate aspects of the term are conflated in discussions of whether blind people have cognitive maps. For example, researchers may use both route knowledge techniques e. However, this inconsistency in the operationalization of the term may also represent a variety of specific spatial abilities.

In order to further investigate the process of cognitive mapping, researchers have also employed neuroscientific methods. Research with animals has found that the medial temporal lobe is critical for the allocentric spatial representations often referred to as cognitive maps that underlie navigation. The PPA is particularly responsive to landmarks at decisions points i. In particular, the RSC integrates egocentric spatial information and may have a role in translating that information into an allocentric code.

Some researchers have opted to conduct the experimental task outside the MRI scanner and analyze the relationship between the structural image and task performance. In addition, researchers have rarely allowed both blind and sighted participants to use their dominant modality in learning or testing within the same experiment see discussion of the relationship between strategy, performance, and ability in the Introduction. In addition, structural imaging studies have found reduced volume in the occipital cortex for blind participants relative to sighted participants , for a review, see Ref With respect to the allocentric network centered in the hippocampus, volumetric studies found that blind people have smaller right posterior hippocampi , and larger right anterior hippocampi , relative to sighted people.

Fortin and colleagues also found that the size of the right hippocampus was correlated with performance on a wayfinding task in a maze. The hippocampus has also been implicated for navigation through a tactile finger maze 46 and an Euclidean distance task comparable to Morgan using auditory cues. However, it should be noted that two of these studies , did not associate hippocampal volume with a navigation task 64 or expertise.

Furthermore, the imaging data from Gagnon and colleagues 46 contrasted maze navigation with rest instead of a control task that could have disentangled the effect of navigation from that of general task completion. A schematic depiction of the neural correlates i.


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Indicators are organized by study and task. The color of each indicator represents study, and the shape represents type of task. Indicators are placed over the approximate regions corresponding to each study. Previous research has also identified a variety of other brain regions e. Specifically, the right inferior parietal cortex was active during an Euclidean distance task using auditory cues, and the posterior parietal cortex was active during navigation through a virtual environment using a SSD.

Other areas may be related to navigation by blind people, but more research is needed before these can be tied to specific spatial knowledge constructs precuneus and fusiform gyrus 47 ; temporal parietal junction ; and superior temporal gyrus The recruitment of these areas by different modalities e. There are three different technological approaches to navigation assistance for blind people.

First, noninvasive technologies including SSDs exploit the brain's natural ability to adapt in response to the environment. Unlike SSDs and invasive technologies, these general aids can potentially be used by people with or without vision. Despite the large number of conceptual papers on this topic, , , , , , , , , , we will focus our discussion on the few examples of SSDs that have been empirically tested in the context of navigation. For more comprehensive reviews of technological navigation aids and SSDs, see Refs 4 , 5 , and SSDs translate visual information into tactile information, auditory information, or both in a noninvasive manner.

Recently, researchers have investigated the potential of these technologies for navigation by blind people. Indeed, congenitally blind participants using SSDs recruit visual areas to recognize sounds, shapes, and movement , see Neural Correlates of Navigation by Blind People section. Since , many researchers have investigated the use of SSDs for locomotion and wayfinding assistance in indoor and outdoor, real and virtual, environments using auditory and tactile feedback.

Some of these SSDs have been tested in the context of locomotion with varying success. For example, the Tongue Display Unit TDU transforms visual information into electrotactile stimulation that conveys the position of obstacles in the surrounding environment. In addition, the EyeCane is a device for transforming distance information into both sounds and vibrations. SSDs have also been developed for wayfinding assistance. For example, Marston and colleagues successfully directed blind participants along real world paths using different auditory displays.

Similarly, Kalia and colleagues conveyed distance information to blind and blindfolded sighted participants with the aid of a digital map and synthetic speech. In addition, some researchers have shown that auditory and tactile virtual reality training can facilitate wayfinding in a corresponding real environment. Before SSDs can be widely applied, we need to gain a better understanding of the navigation abilities of the blind population. Any intervention intended to support navigation by blind people requires an understanding of their needs as a group and as individuals.

Many studies have reported findings regarding the navigation performance of blind people using small sample sizes e. Type of impairment and age of onset can also lead to challenges with the assignment of participants to experimental groups. For example, people with only light perception are often classified as totally blind. The study of navigation strategies provides an innovative way of addressing challenges associated with the heterogeneous nature of the blind population. Previous research has required blind and sighted participants to adopt similar strategies in order to complete a particular task.

However, this approach has led to difficulties in extracting consistent patterns in spatial knowledge acquisition during navigation. While the number of studies on navigation strategies in blind people is limited, 8 , 16 , they suggest that performances on spatial tasks are strongly associated with strategy choice for both blind and sighted individuals.

Such investigations were also limited in the past given methodological challenges such as collecting path information and the manual classification of strategies but see Ref Originally, search strategies were classified by Hill and Ponder as part of orientation and mobility training.

The perimeter e. After initial learning, Tellevik found that blindfolded sighted participants all mobility instructors tended to shift from the perimeter or gridline strategies to a reference point strategy i.

Spatial navigation by congenitally blind individuals

They found that participants who chose one of these three strategies also provided the most accurate direction estimates irrespective of level of visual impairment. In this case, the cyclic strategy was associated with worse performance than the reference point strategy. However, when visual information is available, the cyclic strategy was also related to better performance. The systematic testing of scientific models sometimes requires the adaptation of existing frameworks in order to incorporate findings from disparate fields.

In this review, we have attempted to bridge spatial cognition and visual impairment literatures, including recent advances in neuroscience and technology, in order to gain a better understanding of the navigation abilities in blind people. Towards this end, we proposed that future research should allow for blind and sighted individuals to adopt different strategies that do not artificially limit their potential. We also proposed three models of spatial knowledge acquisition by blind and sighted people and attempted to characterize previous research in these terms.

This procedure highlighted the importance of measuring spatial learning over time in order to assess learning potential in the absence of vision. This longitudinal approach also allows for the investigation of hypotheses regarding amodal spatial representation. Along with existing studies on the functional equivalence of different perceptual modalities, we proposed a line of research on the Bayesian integration of spatial cues from multiple modalities used by blind people.

This is complemented by a review of the neural correlates of navigation by blind people within the context of functional reorganization. The topic of functional reorganization was also considered in light of new developments for SSDs that were specifically designed to aid navigation by blind individuals. Future considerations also included methodological issues resulting from heterogeneity in the blind population and the ways in which they may be addressed with research on navigation strategies.

Conflict of interest: The authors have declared no conflicts of interest for this article. This paper is dedicated to Roger Schinazi. National Center for Biotechnology Information , U. Wiley Interdisciplinary Reviews. Cognitive Science. Wiley Interdiscip Rev Cogn Sci. Published online Dec Victor R. Author information Article notes Copyright and License information Disclaimer. Corresponding author. This article has been cited by other articles in PMC.

Abstract Spatial navigation in the absence of vision has been investigated from a variety of perspectives and disciplines. Open in a separate window. Figure 1. Reference Frames and Scales of Space In wayfinding, egocentric and allocentric reference frames always involve at least one observer, two environmental features, and the spatial relations among them.

Spatial Knowledge Acquisition At the macroscale, researchers have proposed two frameworks for describing the acquisition of spatial knowledge. Figure 2. Multimodal Processing and Amodal Representations Amodality posits that spatial representations can be abstracted from the perceptual modality through which the information was originally acquired. Figure 3. Heterogeneity in the Blind Population Any intervention intended to support navigation by blind people requires an understanding of their needs as a group and as individuals.

Navigation Strategies The study of navigation strategies provides an innovative way of addressing challenges associated with the heterogeneous nature of the blind population. Notes Conflict of interest: The authors have declared no conflicts of interest for this article. Golledge GR. Geography and the disabled: a survey with special reference to vision impaired and blind populations. Trans Inst Br Geogr , 18 — Imrie R, Hall P. London: Spon Press; Sensory substitution: closing the gap between basic research and widespread practical visual rehabilitation.

Neurosci Biobehav Rev , 41 :3— London: Springer; Sensory substitution of vision: importance of perceptual and cognitive processing In: Manduchi R, editor; , Kurniawan S, editor. Assistive Technology for Blindness and Low Vision. Adv Child Dev Behav , 10 :9— Perception , 25 — J Environ Psychol , 26 — Millar S. Int J Behav Dev , 11 — Comparison of nine methods of indicating the direction of objects: data from blind subjects.

Perception , 22 — Warren DH. Childhood visual impairment: perspectives on research design and methodology.

J Vis Impair Blind , 72 — Blindness and Early Childhood Development. New York: American Foundation for the Blind; Chess S, Gordon SG. Psychosocial development and human variance. Rev Res Educ , 11 :3— Schinazi VR. Representing space: the development, content and accuracy of mental representations by the blind and visually impaired.

Blindness and Brain Plasticity in Navigation and Object Perception Blindness and Brain Plasticity in Navigation and Object Perception
Blindness and Brain Plasticity in Navigation and Object Perception Blindness and Brain Plasticity in Navigation and Object Perception
Blindness and Brain Plasticity in Navigation and Object Perception Blindness and Brain Plasticity in Navigation and Object Perception
Blindness and Brain Plasticity in Navigation and Object Perception Blindness and Brain Plasticity in Navigation and Object Perception
Blindness and Brain Plasticity in Navigation and Object Perception Blindness and Brain Plasticity in Navigation and Object Perception
Blindness and Brain Plasticity in Navigation and Object Perception Blindness and Brain Plasticity in Navigation and Object Perception
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