Saturday, April 28, 2012

I Can't Find My Way Out of My Own Backyard

 I really don't have a good sense of direction although not quite as bad as the title of this post would have you believe.  Let's just say that before the GPS was invented that I got lost regularly on well known routes.  I use the GPS all the time... for all my doctor's visits.  Even the ones that I have been seeing for years.

With vision therapy, I have gotten alot better at finding my away around the Hospital of the University of Pennsylvania.  I used to get hugely lost in that insane labyrinth.  Honestly, someone needs to start doing master plans for hospitals.  It seems like they just build those things and then somebody with gazonga money comes along and donates a humongus wing.  The architects just slap the wing on with no regard to any sense of workflow, so you end up wandering around a maze.

Also, when I was in college, I went orienteering with a compass and a map.  I had a hard time learning how to read a topographic map, but eventually I got it.  However, I had a really hard time judging distance and understanding the relative size of hills in relationship to the size on the map.

Not good for the spatially challenged.   But vision therapy has helped alot.  Haven't tried orienteering since.

Let's just say that I assumed that the issue of finding my way around was assumed solved or manageable.

Then, I find that one day my GPS goes on the fritz on my way out to Lancaster. I have been out to Lancaster once a week gazillions of times.  You'd think I should know the way, hunh?   Well... No.
The GPS has crippled me.  I am so used to doing what I am told to do by the GPS that I've never looked at the landmarks around me.  So I got lost and was late.

Now, I am thinking that I really do need to tackle this problem.  There is a fancy name for this:  Topographic Agnosia, a visual agnosia in which a person cannot rely on visual cues to guide them directionally due to the inability to recognize objects. Nevertheless, they may still have an excellent capacity to describe the visual layout of the same place.  Patients with topographical agnosia have the ability to read maps, but become lost in familiar environments.


Comorbid conditions include: CAPD (Central Auditory Processing Disorder), Asperger's syndrome, prosopagnosia (an impairment in recognizing human faces), and nonverbal learning disabilities tend to co-occur with topographic agnosia, because they all affect closely related parts of the brain. In particular, the brain module that deals with faces is known to be located near the place module, so it would make sense that prosopagnosia commonly occurs with topographic agnosia. 

Developmentally, children are thought to develop landmark (or place) recognition.  That is they first learn to recognize familiar places.  The next skill acquired,  route knowledge, describes the information that encodes a sequential record of steps that lead from a starting point, through landmarks, and finally to a destination.

Descriptions of route learning also emphasize its grounding in an egocentric co-ordinate frame. It is assumed that a set of transformations take place by which the retinal position of an image is combined with information regarding the position of the eyes in the orbits and the position of the head upon the neck in order to represent the location of an object with reference to the body. This is termed egocentric (or body-centred) space and is the domain of spatial concepts such as left and right. Orientation is maintained within a learned route by representing egocentric position with respect to landmark (i.e. pass to the left of the grocery store, then turn right). A final, and crucial, aspect of route-knowledge is its presumed inflexibility. Because a route encodes only a series of linear instructions the representation is fragile, in that changes in crucial landmarks or detours render the learned path useless. 


Whereas route-learning is conducted within egocentric space, map-like representations are located within the domain of exocentric space, in which spatial relations between objects within the environment, including the observer, are emphasized (Taylor and Tversky, 1992). A developmental dissociation between egocentric and exocentric spatial representation has been demonstrated in a series of experiments by Acredolo indicating that these two co-ordinate frames are represented by adult subjects (Acredolo, 1977). In order to generate a representation of exocentric space, egocentric spatial decisions must be combined with an integrated measure of one's motion in the environment. While a tree may be to my right now, if I walk forward 10 paces and turn around, the tree will now be to my left. Though the egocentric position of the landmark has changed I am aware that the tree has not moved; the exocentric position has remained invariant. A representation of this invariance is available by combining the egocentric spatial judgements with a measure of the vector motion that was undertaken. 


Because of this representational co-ordinate frame, map-like representations are thought to preserve the Euclidean relationships between places in the environment. Thus, angle and distance relations between landmarks are readily available. In addition, maps are inherently flexible. This is a feature emphasized by O'Keefe and Nadel: `Whereas a route specifies a starting point, a goal, and a particular direction of movement from the former to the latter, a map specifies none of these, either in its construction or its usage. It can be used with equal facility to get from any particular place to any other. Additional flexibility derives from the freedom from specific objects and behaviours. If one path is blocked another can be easily found and followed.' (O'Keefe and Nadel, 1978, p. 87). 

So, how does this apply to me?
Until vision therapy kicked in, I focused on the back of the car in front of me.  I just didn't have the field of vision to notice what was around me.  I knew landmarks but I could pass them by because I just didn't know what was going on around me.   I can close my eyes and point to things correctly in a room.  I can tell you how to get to my doctors' offices.  I just can't drive there.

I'm more like the cab driver in Takahashi's study:

. . as he was driving his taxi in the same city [in which he had worked for 6 years], he suddenly lost his understanding of the route to his destination. As he could quickly recognize the buildings and landscapes around him, he was able to determine his current location. However, he could not determine in which direction he should proceed. He stopped taking passengers and tried to return to the main office, but didn't know the appropriate direction in which to drive. Using the surrounding buildings, scenery, and road signs he made several mistakes along the way. He remembered, during this time, passing the same places over and over again.

or, Patient MB:
`I was returning home when suddenly, even though I could recognize the places in which I was walking and the various shops and caf├ęs on the street, I could not continue on my way because I no longer knew which way to go, whether to go forward or backward, or to turn to the right or to the left . .

I wonder if I have exocentric topographic agnosia.  I just patients can't  recall (or form) a link between directional information and landmark identity.  I just lose my heading.  Hmm... I wonder if this is a visual memory problem or a problem with time passage.  Another possibility is  that I am not able to maintain direction through  landmark, vestibular and idiothetic (self-motion) cues.

I wonder how much of this is related to lack of binocular vision.  If you can't see space, it kind of screws up your orientation to it.


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