In particular, my ability to think was gradually expanding, and I could do so with less fatigue.
Zelinsky’s glasses had given me access to new paths in my brain, and the work with Donalee was pushing my brain to grow and develop along those new channels. The plan made sense. The work made sense. The results were coming.
Thank you, Donalee—you called me back!
DEBORAH ZELINSKY AND THE MIND-EYE CONNECTION
Before we return to Zelinsky’s lab to delve into the fascinating world of an optometrist whose work is based on neurodevelopmental research, it’s important to first learn something about how the human visual system works. Then we’ll walk step-by-step through my recovery using what we have learned to explain the details of why treating my brain’s visual system was so crucial to my recovery.
A QUICK TOUR THROUGH THE VISUAL SYSTEM. There are three retinal processing pathways through the brain. Two of these, for central vision and peripheral vision, are for eyesight and are processed in the brain’s visual cortex. The third is for non-image-forming retinal signals (also primarily from the peripheral part of the retina) that branch off and are processed by other body systems such as for posture control, for sleep rhythms, for the production of melatonin, etc. Each of these is crucial to our well-being, as is the coordination among them.
There are roughly 100 million receptors in the retina of each eye, which respond to light, but there are only a million axons leaving the retina, so the many layers of the retina together act as a very sophisticated sensory filter. Additionally, the retina acts as a transducer that converts light into neural signals: input photons of light enter through the lens, pass through a chemical stage in the early retinal layers, and then move on to a later electrical stage comprising the neural signals sent out along the axons. Axons are bundled together, depending on which area of the retina they come from, and this also determines the route they will be taking through the brain. The collected bundles of the one million axon output fibers form the optic nerve for each eye.
Vision signals spread out and are routed along many different paths known as optic radiations to the back of the brain where the visual cortex resides. Different parts of the visual cortex process, first, movement, location, size, and shape from the peripheral vision, and, second, lagging just slightly behind, colors and details from the center vision (though see the footnote here). This is what is classically thought of as the “visual system.”
Thus we have a chain of crucial steps in translating light into meaning: how light is transmitted through the clear cornea and lens of the eye, how the various sections of the retina are activated, how the photoreceptor signals are reduced to the axon output, how activation is dispersed among the various axon bundles in the optic nerve, how the signal is routed to the visual cortex, and how the signal is passed on by the visual cortex to the rest of the brain, which gives it meaning.
But we are not done. In the past ten years, retinal research has shown that there are many other non-image-forming pathways from the retina to various body systems. These channels affect the “homeodynamics” (dynamic self-organization) of the body—through hormones, enzymes, and other mechanisms. For example, there are receptors linked with thyroid function, pupil dilation and constriction, dopamine production, and adrenaline production. Consider that when light cycles change we can experience jet lag, or seasonal affective disorder, and those who are completely blind may have to deal with circadian rhythm challenges because of non-24-hour sleep-wake disorder. One can easily understand the powerful effects of this non-image-forming retinal input as follows: imagine that a gigantic spider suddenly crosses into your peripheral field of vision. A jolt of adrenaline will begin flooding your body well before your conscious mind interprets the threat. In fact these non-image-forming retinal signals are always given precedence: the signals travel faster and are processed first; when our bodies are under high stress we often cannot pay attention to what we are seeing with our central-image visual processing.
And for each of these paths, a complex network of feedback signals continually biases the whole system—altering the information that is passed on to the brain.
Ultimately, almost every part of the brain gets involved, because the processing of visual/spatial information is linked to symbolic thought, body sense, motor coordination, memory, balance, hearing, and so on. Along the way to the visual cortex, signals from other sensory systems are integrated, such as those for hearing and proprioception.
Nor can the retinas be considered as simply input devices, because signals also return to the eye in response to cognition and body states (such as emotions), to make significant chemical and electrical changes in the retina, and to control both eye movement and filtering in the retina. For example, a depressed person may have signals returning to the eye shutting down peripheral awareness (shutting out the world), whereas a person with ADD might have signals emphasizing peripheral awareness (distracted by everything). In this way, vision is a complex process, closely integrated with the inner workings of the brain. Note that when we are not looking at anything at all, but simply thinking, our eyes will move in very specific ways according to our thoughts. From a scientific standpoint, our eyes really are windows into our souls.
In her practice, Zelinsky alters the input into each of the two eyesight systems, as well as into the non-image-forming retinal systems, makes very sophisticated measurements and observations of the resulting output, and then uses this information to make deductions about the likely nature of the brain processes leading from the former to the latter.
Critical to Zelinsky’s work—as we will see shortly—is the idea that by activating different parts of the retina, she can alter the paths through the optic radiations that the retina’s eyesight signals will take on their way to the visual cortex, and also the paths of the non-image retinal signals that branch off from the optic nerve before they get to the optic radiations.
There are three ways that Zelinsky uses light to alter the way the brain operates. First, she can bend the light to different parts of the retina, which, ultimately, activates bundles of axons differently. In other words, the same visual/spatial signals are being sent, but they are being filtered differently (in the reduction from 100 million to 1 million in the retinal layers), and are being routed differently (through different bundles of axons). When we consider that 100 million receptors are packed into about a square inch of the retina’s surface area, it is obvious that even very small changes in the optics can make a huge difference in which receptors are being activated.
Second, Zelinsky can change the frequency of the light by allowing different colors through to the retina. Roughly speaking, when the frequency of the light changes, different frequency-sensitive photopigment chemicals, such as melanopsin (~480 nanometer wavelength sensitivity) and rhodopsin (~500 nanometer sensitivity), cause different photosensitive receptors in the same area of the retina to become activated. Thus, while the light may still be hitting the same part of the retina, different cells become activated, ultimately changing the output signals in the optic nerve.* The science of this process of frequency filtering gives new meaning to the phrase “seeing the world through rose-colored glasses.”
Third, Zelinsky can selectively block signals from reaching the retina at all through using occlusion filters that simply reduce, or block out, the light to certain parts of the eye.
With change either to the location of where the light strikes the retina, to the frequency of the light striking it, or to the amount of the light striking it, the result is that the signal load is dispersed differently through the pathways in the brain.
This is where the principles of brain plasticity—one foundation of modern brain science—come into play. When the brain is damaged, such as from TBI, it is possible that the retinal output signals might be fine, and the visual cortex might even be in good shape, but the pathways between the two, or the areas around the pathway
s with which the axons interact, are damaged. Signals along the old paths are degraded (think of “picking up static”) because of the permanently damaged tissue. By bending the light in the eyes, selectively occluding it, and changing the frequency of the light, Zelinsky is able to avoid the damaged routes along which the visual/spatial signal travels.
To greatly simplify this staggeringly complex system, considering eyesight only, let’s imagine that there are only one hundred different paths along which signals travel from the retina to the visual cortex. Now let’s imagine a patient with brain damage from TBI for whom twenty of these paths have become permanently damaged. On suspecting this, Zelinsky would try to change the input to the eye so that the eighty remaining paths were emphasized and used more heavily, and the twenty defective paths were avoided, in carrying the same signal to the visual cortex. Think of rerouting traffic from a highway, U.S. 25—which has been damaged—to highways U.S. 40, U.S. 50, and U.S. 60—which are still in good shape. The same traffic is getting through, but it is taking a different route.
Through habituation, when the new pathways through the brain are established, the healthy tissue adapts, and the magic of the brain’s plastic nature takes over. Within a very short time the new brain tissue learns its new tasks in conveying the visual/spatial signals to the visual cortex. Because it is healthy, the signal path is once more restored to its full capacity without distortion. And, once the brain learns to process the signals along the new paths, the need for the remedial help in “jump-starting” the new paths may become unnecessary.
This explains why I tried many kinds of brain exercise over the course of eight years, but only experienced distress, and pain, with even the simplest sorts of intellectual tasks: I was simply repeatedly sending signals along the old, well-worn, but now damaged, paths.* And this is why the standard medical response for brain damage is “learn to live with it, because you’ll never get better—no one ever does.” And yet, within two weeks of getting my first pair of brain glasses, my plastic brain had reconfigured itself, learning to follow healthy pathways through to the visual cortex—and I was vastly, hugely improved. Additionally, although I can’t claim it as part of the science, it is my strong intuition that the constant onslaught from bad visual/spatial signals required parts of my brain to simply shut down because the input was too exhausting to process. Once the signals were sorted out, those parts of my brain—used in complex spatial cognition and symbol manipulation—could come out of hibernation.
WORKING WITH AN OPTOMETRIST EMPHASIZING NEURODEVELOPMENTAL REHABILITATION. Having laid the foundation, we can now walk through the processes that Zelinsky uses to translate her knowledge of the image-forming and non-image-forming retinal systems into the practical matter of making people’s brains function the way they were intended. The first step is determining the current state of a patient’s brain, and for this Zelinsky uses an extensive battery of tests, along with intuition based on her years of clinical experience.
In that first trip I took to Zelinsky’s office, I went through more than fifteen different visual/neurological testing procedures, some of them formal, and some of them less so—but still important information for Zelinsky, who was looking for subtle clues to my brain’s organization. Many of the tests were repeated in subsequent visits, with Zelinsky looking for checkpoints as she pushed my brain processing in a very specific direction.
After my brief introduction to Zelinsky, I filled out a long set of questionnaires, and also wrote essay responses about my habits and my specific complaints.* Based on my responses, Martha asked me a series of further questions that helped to diagnose my lifestyle, which in turn gave clues about the organization of my brain. I also brought along several pages of notes on my TBI symptoms that Martha read, summarized in my chart, and then passed on to Zelinsky. I later discovered that Zelinsky always read everything I brought her.
The first test Martha gave me was called the Padula Visual Midline Shift test. I was told to look straight ahead. Then Martha brought a horizontally held chromium steel shaft, like a skewer for a barbecue, from above down toward the ground so that it gradually entered the middle of my visual field.
She said, “Tell me when the shaft is directly in front of your eyes.”
She then repeated the movement, but this time from the ground upward. In this way my top-to-bottom midline was determined. The exercise was then repeated from left to right, and right to left.
In normals, these stopping positions will be about the same, and the midlines—horizontal and vertical—will intersect at a crossing point directly in front of a person’s eyes. For those of us with TBI or other brain oddities, the midline may be shifted higher or lower than normal, to one side or the other, or both. In other words, the internal 3D spatial world is no longer lined up with the world coming in through the senses.
According to William V. Padula, the designer of the testing mechanism, when a person has a midline shift—associated with the ambient visual process*—she may have balance and coordination problems, and have trouble making out the details in a visual scene.* Without grounding in this non-image-forming and peripheral retinal processing, the world may become broken into isolated parts, such as what happened to me whenever I went shopping: all the items on the shelves are suddenly experienced as a kaleidoscopic nightmare of overwhelming detail without any context in which to sort them out. The central eyesight processes then have to take over, trying to make gestalt sense of the scene—performing tasks for which they were not designed, causing motor responses to become slower and slower. Cognitive confusion and distress can also result.
I tested normal on the Padula midline test. But as we have seen from previous chapters, I experienced every one of these rather startling symptoms—for reasons other than a midline shift—on a regular basis, suggesting that there were other problems to be found with my ambient visual system.
Next, in the Yoked Prism Walk, Martha gave me a pair of thick prism goggles to wear, and then observed my gait as I walked down the hallway and back four times. Before each trip she adjusted the goggles to a different orientation.
Figure 12: Prism Glasses—Top View with the Yoked Prisms Shifting Images to the Left
Experientially, prism lenses bend the room in a “fun house” way, tilting it up, sloping it down, and bending the top and bottom in a great arc to the left or to the right, depending on the orientation of the prisms. (“Yoked” means that the prisms are oriented in the same direction.) Although in all cases the visual scene will look altered, patients may have widely differing abilities to walk down the hall from one orientation to another. In my case bending the floor up, and tilting it down, or bending the light from the right, was slightly disorienting, but I was almost immediately able to adjust and navigate the hallway. When the light was bent from my left, though, I became completely disoriented: I had trouble walking and I ran into the side of an open doorway along the way. Such difficulty with one of the lateral orientations is typical for TBI sufferers.
In writing about this test, Zelinsky explains that the Yoked Prism Walk evaluates gross body movements at a reflexive level, as well as spatial orientation, while the patient is moving. It can demonstrate how poor stability may impair higher-level perception.*
The distinct discrepancy between my performance with the prisms bending the light left versus bending it right was important—especially when linked to the similar problem I reported, in my notes, of growing dizzy when turning around in one direction, but not the other. This may also have been linked to the phenomenon, discussed earlier, that under brain stress, I was unable to turn to my right at all: I simply could not conceive of “right-ness.” And, it may explain other anecdotal aspects of my life as well. For example, if I went running with my daughter, I had to orient myself on her left side; when I was on her right, I would start to get dizzy almost immediately.*
Martha next gave me an Asymmetrical Tonic Neck Reflex
(ATNR) test. “Stand up and hold your arms out in front of you,” she said, “like Frankenstein, with your fingers extended . . . Okay. Good. Now turn your head to the left, and then to the right.”
ATNR is an innate survival reflex, seen in infants, which often reemerges in adults as a protective mechanism after a shock to the nervous system, such as from TBI. If the subject lowers his opposite arm when turning his head, this suggests a shock has occurred. In my case, an ATNR was present when I turned my head to the left.
Martha then assessed my extraocular muscles—the six muscles that move the eye—using pursuit tests, where I tracked the eraser-end of a pencil with my eyes while keeping my head still. She had me follow various patterns, including a big H. Martha was looking for any partial paralysis in my eye movements, and also observing my anticipatory eye movements in predicting the path of the target—which gave clues to the peripheral awareness in my brain. Was I able, without thinking about it, to predict the path the eraser was going to take, and adjust my eyes to smoothly follow that predicted path? In my case I had no problem following the pencil, even though, as we saw previously, following a baseball when playing with my boys was extremely fatiguing. The pursuit test results would prove to be important in interpreting the results of later tests.
Martha next gave me a Near Point of Convergence test by bringing the pencil close to the bridge of my nose, and then, afterward, the LANG-STEREOTEST II to check my stereoscopic vision and depth perception—both of which tested normal.
Lastly, Martha gave me a King-Devick Test, in which I read a series of single-digit numbers on two pages. One of the pages just had the numbers on a white background, and the other had lines inserted between one number and the next. The test is used to look for deficiencies in saccadic eye movements (extremely rapid, intentional, simultaneous movements of both eyes in the same direction), which can be an indicator of TBI. Tests like this are often used to obtain a quick, objective sideline diagnosis of concussion in football players and other athletes. I tested normal on this exam.
The Ghost in My Brain Page 21
