"...the geographer Graham (1982, "Maps, Metaphors and Muddles", The Professional Geographer, 34, 241-260) has said that the term "mental map" (often used as a synonym for "cognitive map") is perhaps one of the most unfortunate in the literature, having been applied to everything from an individual freehand street map of a neighborhood, to textbook illustrations expressing the environmental preferences of whole groups of people..." (from Spencer, Blades, and Morsley, 1989).
One way to define the profession of orientation and mobility is to relate the field to the science of navigation, getting vehicles like ships and trucks to their destinations. Navigation, from this perspective, is about finding the way, avoiding collision, conserving energy, and meeting schedules. Orientation and mobility is about human navigation: teaching blind individuals to find their way, to move about safely, efficiently, comfortably, and accurately. Like the science of vehicular navigation, different professional perspectives provide helpful ways to think about navigation. Below is a sketch of different perspectives offered by other professions.
I often tell stories about the navigational skills of the first student I worked with as a public school mobility specialist. I can see Scott, a teenager when we met, walking down the dead center of the middle school hallway, books under one arm, no cane, head up, weaving through vibrating, noisy crowds, passing door after door, and then magically turning at his classroom doorway, strolling into class, walking directly to his desk and sitting down, all this without running into walls or other students. After watching this performance over a period of weeks, I asked Scott how it was that he could travel so well. Specifically, I wanted to know how he could walk down the dead center of a hallway.
"Well," he said, "It's because I hear the walls. I balance the sound in each ear, so I stay exactly in the center of the hallway. When I was a kid, I woke up one night feeling peculiar. Then I realized it was the walls, I could hear them. I've been listening to walls ever since. Actually, it's more subconscious. I don't listen to the walls, I just sense where they are."
A large part of the human brain is given over to a subconscious navigational system that controls and monitors movement. During human evolution it became necessary for the alert, conscious part of the brain to look out for danger, to hunt for resources, to communicate with others, and to solve problems. Conscious movement, however, is slow and labored. Animals that had to think about each foot step quickly became extinct. Navigation became an unconscious skill for the survival of the species. The goal of the mobility teacher is to help blind students become so proficient (through practice) that navigation becomes (as it is for sighted peers) an unconscious activity.
Human beings effortlessly move through space primarily because the vision system is superbly adapted for navigation. The peripheral processing area of the vision system continually monitors optical flow (movement). It sends data to the parietal lobe on the right side of the brain where spatial relationships are mapped and remembered. At a glance, the vision system can register the position of objects in a spatial area, and map routes to or around the objects. Human beings have the ability to quickly determine the position of an object in space, and to point to it. We also have the ability to estimate how far an object is from us, and we have the ability to estimate how far two objects are from each other. Vision lets us instantly calculate whether objects are nearer or farther, higher or lower, more to one side or the other. A more conscious, central processing vision system quickly determines the size, length, and color of an object, and does so in three dimensions.
Blindness, the absence of this sophisticated vision system, is a state where there is a relative paucity of information about the world. Blind students must spend more time exploring space and examining objects to arrive at the same spatial understanding as a sighted person. To interact with the environment (to reach for objects, walk around objects, pass through open doors) the sighted individual uses a viewpoint-dependent representation of the world. From any position, and after each change in position, the sighted person instantly sees how the world has been repositioned, how objects have changed in relationship to movement (the sighted persons movements or the objects movements). Blind individuals do not have an instantaneous viewpoint-dependent representation of the world. Blind students must build mental maps of layouts and of routes, and make future projections along the route based on non-visual memories. Blind students have to learn how to explore, and they have to spend more time actively researching their environment. Even with the loss of vision however, blind individuals can become amazingly capable travelers.
After graduating from high school, Scott took a job with the Internal Revenue Service in Washington D.C. Two years passed, and I had a chance to go to Washington for a conference. I gave Scott a call and we agreed to spend a day together. When I got to the big city and settled in my hotel, I spread the subway map out on the bed and tried to figure how to get to Scott's apartment in Virginia, at the very end of a subway line. I finally gave up and called him. I still remember the ironic smile that crossed my face as he patiently explained the layout of Washington, all the changes on the subway, timetables and fares. Saginaw, Michigan, where I taught Scott mobility, has no subway system, no massive rush hour, no crushing swarm of humanity, no impatient gridlock of cars, buses, trucks, bikes, motorcycles, and no beggars pulling on your sleeves. Somehow Scott took what he learned from experience and from our small town lessons together and managed to become a competent big city commuter.
Everyday on his way to work he followed the same complex and challenging route. He walked three blocks from his apartment to the subway station, rode the train to the middle of Washington, changed underground levels, transferred to a second train, and exited near Pennsylvania Avenue. Then he walked six more blocks to the I.R.S. building, took the elevator to the top floor, found his office, his desk, and went to work. Now that's a story I love to tell. It's the answer to the question: "How well can blind individuals learn to travel?"
Whether sighted or blind, human beings need references landmarks. Imagine a world in which everything is random, a world with no edges, no patterns, just a swirling, churning morass. This would be a world with no faces, no objects, no form. Navigation would not be possible (neither would identification).
If we now grant the world one form that drifts ainlessly in the random swirl, we can have identification, but still no navigation. Only when we anchor the object to a position in space, with Euclidean (geometric) coordinates, can we move our bodies in relation to the object. We can orient ourselves, put our body facing the object or to the left or right. We can approach or move further from the object.
Frames of reference are necessary for orientation and navigation. For the blind individual these reference points are simply non visual, but they are used in the same manner to anchor the body to spatial coordinates. These reference points are called landmarks (or clues, if they are intermittent), and the significance of these landmarks is a critical understanding that blind children must be taught.
Navigational impairments arise in a number of ways, from poor collecting and neural coding of visual information, to impaired long term memory of spatial scenes. Most navigational impairments appear to be due to right parietal lobe damage, or to occipital/ temporal cortical involvement. It is interesting to make the association that these tracts, the parietal and the temporal correspond to the split in the visual processing streams. The duplicity theory of vision (roughly, that there is "what is it" temporal processing system, and a "where is it" parietal processing system) would seem to suggest that (at least) two fundamentally different kinds of spatial disability could exist. It is also tempting to make the over-generalization that there might be a right brain, holistic, scene driven knowledge of space that could be impaired with brain damage, and a left brain sequential route following knowledge od space that could be specifically impaired.
Damage to the hippocampal region results in a failure to remember spatial layouts or landmarks. Parietal lesions affect spatial orientation, while lesions to the occipital/temporal area result in poor environmental recognition. In a condition called unilateral neglect, patients can respond to left or right stimuli individually, but when presented with simultaneous (bilateral) stimulation (like in the real world), one side is consistently neglected. Right parietal damage causes sensory events on the left side to have little or no impact on awareness. Parietal damage reduces the ability to disengage and shift attention to a target located in a direction opposite the side of the lesion. Parietal damage to the right hemisphere impairs global processing; the ability exists to copy small letters, while missing overall forms in space. Parietal damage to the left hemisphere impairs local processing; the ability to resolve overall form in space is intact, but the patient misinterprets small objects. Environmental agnosia is a condition where people get lost in familiar places (home, neighborhood). These patients always have pathology of the medial aspects of the right occipital lobe. Glioma of the right temporal lobe causes marked difficulties finding and using routes. People with apperceptive visual agnosia can identify colors, light intensity, direction, and the dimensions of visual stimuli, but they cannot recognize objects visually (unless tactile or auditory clues are provided). They also cannot identify faces visually. With associative visual agnosia, there is a disconnection between the visual sensory areas and the dominant hemispheres language area. These people cannot name visual stimuli, but they can copy. Palinopsia is visual hallucination in which an image persists or recurs after the stimulus is gone. In Balint's Syndrome there is a disturbed ability to reach out and touch an object, inability to change gaze volitionally, and simultanagnosia, where a patient appears to see and report only a portion of a complex scene. Most of these visual disorders interfere with the ability to find or use landmarks for navigating.
There can be an amazing, and sometimes bizarre collection of brain impairments that impact on navigation. There can be a perceptual loss of depth perception, where objects appear like moving cardboard cutouts. A functional tunnel vision can develop from high level lesions where people have difficulty perceiving whole objects at a glance. Some persons have difficulty on a route if they don't verbalize the landmarks first. On the other hand, the ability to visualize and articulate a route may be present, but the ability to navigate may be damaged. There can be problems retrieving topographical knowledge (as opposed to having lost the knowledge). In general, a person can fail to grasp a route because of failure to correctly encode spatial information, failure to translate the code into action, or failure to retrieve learned codes.
A person with a right brain lesion might not be able to say which of two objects is closer. Impaired judgement may be severe for only near space, or only intermediate space, or for far space. It also appears there are two separate visual association systems for orienting oneself in space: one allows for the processing of artificial visual orientation, like map reading; and a second system forms environmental concepts and route formation. Impairment to either area seriously affects navigation.
There are visual integration problems where parts of systems may be intact, but the ability to integrate is lost. A person can perceive a nose, eyes, ears, etc., but cannot put it together to make a face. The same person may perceive a chair, a window, a bookcase, but fail to put the images together to create a meaningful spatial layout.
Students with navigational impairments, like those described above, can learn to be better oriented using procedures and strategies designed to teach navigation to blind individuals (attention to landmarks, chaining, concept training, positioning the body in space, building mental maps, etc.). Some severe brain impairments, particularly to the hippocampal region and the associated parahippocampal gyrus result in navigation disabilities that cannot be remediated through training. Stroke patients and people with Alzheimer s disease often fit in this category. Evidently,ye the hippocampal area is severely affected when blood flow is reduced from damage.
Teaching blind children (or navigationally impaired children) to become, and stay, oriented in space involves six conceptual divisions (listed below). These are the main topic areas of the navigation home page.
Exploration and play
Gaging initial position
Setting a course (planning the trip)
Monitoring travel along a course
Remembering layouts and routes (recalling and using mental maps)
Navigating defined spaces
The veering tendency off blind pedestrians (Guth and La Duke); JVIB Sept/Oct 1994, Vol 88 #5
It is widely believed that veering decreases as ones walking speed increases (this has not been substantiated)
Lost humans tend to wander in circles when no orienting influences are present (so veering is normal for humans when they are disoriented; so blind veering is a natural consequence of loss of orienting cues because of blindness).
From Baker: "Navigation and the 6th sense"
Cairns, heaps of rock, have been placed as artificial landmarks to mark routes throughout history. In the woods the indians would break or bend (tie back) branches to mark routes.
" a multitude of animals use the sun for orientation"
Primitive peoples maintain a high awareness of where home is as they travel, frequently looking back to assess the changing look of landmarks, and noting changes in the direction of travel.
There is a long rich history of navigation (exploration) that seems inherent in the human soul, blind navigation is part of that rich heritage.
The magnetic sense if unconscious and therefore? part of the human unconscious navigation system.. Does the magnetic sense become more important for blind children? Can the children be taught to use this sense. Remember that the kinesthetic sense and the sense of time are also subconscious but can be taught. Without training, for example, the sense of time is imprecise. With training, it can be used for navigation.
The magnetic sense may play the role of maintaining a rough sense of direction between each conscious check of location.
"The major conclusions drawn from the Manchester and Bernard Castle experiments are that females are more capable than males at non-visual, route based navigation, but that males are more likely to reinforce route based navigation with location based navigation."
From JVIB March/April 1995 "Spatial Orientation and Congenital Blindness: A Neuropsychological Approach" by I. Stuart
"...a number of case reports have confirmed the existence of disorders of landmark recognition (Hecaen, Tzortzis, Rondot, 1980; Pallis, 1955; Whitely, Warrington, 1978), and evidence has been presented that implicates the inferior and medial surface of the right temporo-occipital area (Habib, Sirigu, 1987; Laudis,Cummings, Benson, palmer, 1986)."
"...the right parietal lobe mediates ideas of directionality in space and damage to it causes an impairment in the ability to appreciate spatial relationships between objects or positions in space." This is supramodal meaning that it also affects other sensory systems, most notably the tactual.
"The right hippocampus consolidates these spatial relationships into a permanent memory store that may be expanded to include more complex routes.
1. all subjects tested could walk a tactually presented shape.
2. there is a close association between the ability to read braille and the ability to navigate in space.
The right parietotemporaooccipital area "is concerned with the ability to form an invariant representation of the angular deviations from the vertical that are made by limbs in the course of movement in two and three dimensional space. The integrity of the right hippocampus adds the capacity to establish these representations in a permanent form, so they can be elaborated into patterns of increasing complexity that form the basis of movement in physical space in the absence of vision."
"...the proprioceptive system may be the primary agent in the elaboration of concepts of space, with vision playing a minor role."
"...developmental disorders, together with prematurity and a low birth weight, carry a high risk of focal brain damage. Thus, children who have lost vision as the result of ROP or developmental disorder may suffer damage to the very structures that could help compensate for their visual loss."
1. The limbic system is synonymous with the mammalian (middle) brain and is specialized for emotion and coordinated movement(spatial perception?); the reptilian brain consists of the spinal cord and medullar regions and controls reproduction, breathing, digestion and circulation. these two brains are unconscious. the cortex is the higher brain, the learning brain.
2. the left brain is more a sequential processor, the right brain more in parallel, holistic, gestalt
March April JVIB: "Small-scale versus large-scale spatial reasoning: educational implications for children who are visually impaired" by Lance Potter.
It is not until about the age of nine, according to Piaget that children are able to make the cognitive leap from small scale representation of space (maps and models) to real, large scale environments. Therefore, a blind child should not be expected to comprehend that a map or a small scale reproduction represents a larger space until at least age nine (4th grade). IE. map skills and modeling is a middle school activity (or late elementary).
Remember that blind children lag behind in their cognitive development often, so 4th grade may be too soon.
In sighted kids the ability to form geometrically accurate large scale environmental concepts develops between the ages of 7 to 11 years (Piaget's concrete operational stage)
Before age nine a child can be expected to learn routes, but not travel independently through unfamiliar areas
(this is about geometric reasoning translated into different scales; this author uses the term Euclidean concepts, terms, spaces; should I be doing more to teach shapes, angles, etc. ie. geometry? where is the brain level site for this?)
specific parts of the brain are associated with either small or large scale spatial reasoning
To create a mental map requires that a territory be staked out, with boundaries. Exploration (active moving, study, research, asking questions) establishes a home range, familiar area, and familiar area map.
the question is: how do blind individuals create a mental map? Movement patterns? How are sound positions remembered? How are the relative positions of objects visualized as the blind person moves through space. Does the mental map consist of landmarks, their spatial relationships, and a set of instructions for movement between important sites.
A mental perceptual flow can become a mental map; the blind person has a sense of the landmarks flowing past (do we teach this?) and a sense of direction
"When it becomes unconscious (travel) I go on kinesthetic /time memory, rather than using landmarks"
Dan's notes from interview:
"I don't use clues much, I like things that are going to be there 99% of the time"
"Routes become subconscious after I travel them a lot"
"In my house the pattern of the carpets gives away my position."
"Paths are easy to create in the snow (shoveled paths, tire tracks, etc.)"
"I use the sun a lot, wind, surrounding landmarks to gage initial position"
"I get a bare, sparse set of landmarks in a room and understand their spatial relationship. Them I can mentally project routes in between."
"You don't need to motor plan over familiar routes; I pre-plan if changes have occurred (it's rush hour in the halls, sidewalk sales at the mall, etc.)"
the kinesthetic sense is a distance judgment system, it has to work with a sense of time passed for accurate subconscious travel.
Dan lists the cane as a self-defense weapon; "If it's all you have; that's why you should use a heavier rigid cane for city travel, or night travel"
Kids should not cross streets independently until cane skills have become subconscious
An umbrella is a good mobility device
Winter travel: do not use telescoping or folding canes, they are not strong enough, they bend or break when probing under the snow; folding canes get snow and water in the joints; which then freezes and expands to loosen or break the cane
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