Vertigo And How It Reveals The Priorities Of Sensory Input

A few years ago I found myself suffering from vertigo for a few weeks. It past, and since then it has returned a couple of times for a day or two. That first bout was intense and it complicated my life considerably. Fortunately it was just benign paroxysmal positional vertigo (BPPV) which can be helped with some very specific head movements that help to reposition the otolith (crystal-like substances) to their normal position in the utricle (a part of the inner ear). Basically, to help with balance, spacial awareness and proper body orientation, the vestibular system in the ear contains crystals that move freely in the fluid. Given that the crystals have a higher density than the fluid, they sink causing them to stimulate hair cells. When the head moves, the crystals move, being pulled downward by gravity, resulting in them stimulating different hair cells. This way the brain always knows what way is down and it always knows what way the head is orientated relative to the pull of gravity.

With BPPV, the crystals become dislodged and move into one of the semicircular canals. As a consequence to this, the brain has extreme difficultly interpreting the information that is coming from the vestibular system because it is scrambled / ambiguous – whereas the crystals would normally stimulate a lot of hair cells in one area that corresponds to down, the absence of the crystal means there is less stimulation in a specific direction, and more stimulation in general. The brain assumes it is orientated in many directions at once, which isn’t possible, and this causes the symptoms of vertigo. While not exactly the same thing, about one third of people who experience weightlessness will suffer from a type of motion sickness that is believed to be caused by the elimination of down. The crystals float which isn’t necessarily a problem. However, when the person changes direction, the crystals impact the hair cells in a different way than normal – the force vectors are direct (straight) and not impacted by the pull of gravity (forward or back with a downward angle). The brain adapts to the change very quickly and the motion sickness disappears after a day or so.

Fortunately for me, the resetting movements seem to help. The nausea, which had been very strong the first week faded and just went away. What remained was an intense dizziness when I move my head suddenly, or when I would lie down or stand-up. I went to the doctor and he said that it would normally pass after a few weeks. If there was a virus going around that was causing it, my body would take care of it, and if it was BPPV the movements would take care of it. He didn’t know, but since there was no obvious pathology in terms of my ears being injured or infected, there wasn’t much anyone could do. Welcome to middle age was about all his smile said.

His answer was par for the course and about what I had expected. So as unsatisfying as I found it, I didn’t have any choice but to accept it, get back to life and wait for natural healing to occur. And of course this meant that I would be hyper aware of whatever was going on and whatever changes occurred until I was back to normal.

This was for me the most interesting part of it. Step one was to learn about what was causing the vertigo (the explanation outlined above). Step two was to learn about other ways the system might break down even when it was working fine (the zero G motion sickness stuff). The final step was to be curious how my brain would adapt to deal with what was going on. If the brain of an astronaut took a few days to adjust to the changes in sensory input coming from their vestibular system when “down” was eliminated, what was my brain going to do in response to the scrambled input it was getting? No matter how bad I felt or whatever interpretation I was giving to my experience, my brain was going to try and make sense of the input it was getting, simply because that is what brains do.

Since I wasn’t feeling nauseous any more, life was just more difficult. It would have been nice and of course I would have liked to not be dizzy anymore, but that wasn’t going to happen simply by wishing it away. There was a tiny chance that I would never return to normal, a thought that I didn’t like but had to entertain if I was going to be pragmatic about things. IF this was going to be the rest of my life, WHAT did I need to do to reduce the dizziness? Doing something about it was important for reasons other than the feeling it created, the bouts of dizziness were mentally draining. It takes a lot of effort to remain standing when it feels like you are tumbling through the air. The sensation doesn’t match reality and the amount of work that is required to reconcile the conflict and make the accurate determination that I was standing upright was exhausting. The exhaustion was a symptom of the work being done, and when all is said and done, it’s exactly what I needed my brain to do. It was now on me to help it out as much as I could.

A long time ago I watched a BBC program about the functional plasticity of the brain. It covered the Innsbruck Goggle Experiments of Theodor Erismann (1883–1961) and Ivo Kohler (1915–1985). In their studies, they gave the subjects glasses that flipped all of the visual information and made it upside down. The subjects were then asked to wear the glasses during all of their waking hours for the next few weeks as they went about their lives. As you would expect, that first few days were very challenging for the subjects. They had a lot of difficulty interacting with the world. While they were able to pick things up, they had a lot of problems moving their hands into the right position to grab the objects. Moving objects were nearly impossible to track at the beginning and were impossible for them to touch. Walking was extremely difficult and no one was allowed to drive.

But very quickly the subjects began to get the hang of it. After a few days writing became easier, they figured out how to locate and manipulate objects, and moving around stopped being a trial and error type experience. After 10 days, one of the participants was able to ride a bike without falling and without fear of running someone over or riding somewhere they didn’t want to go. It was remarkable to watch their progress and notice the daily improvement in acquiring functionality and then automating it after some period of time.

When the study was over and they were allowed to remove the goggles, they did not immediately return to normal. They found it difficult to interact with the world again, not nearly as tough as they had found it when they put on the goggles, but it wasn’t automatic and unconscious. But after about half an hour, things just seemed to pop into place and their pre-experiment proficiency was restored and everything seemed to return to normal.

In my own life I have experienced a similar type of thing, just a lot less intense or overwhelming. Any time I buy a new bike, my brain is forced to adjust to the new geometry and riding position. For the first few rides I am a little shaky and need to take it easy to make sure I don’t fall, but after a week or so it doesn’t feel odd and I have no difficulty maneuvering the bike on rough terrain and over logs. When I get back onto my old bike, it feels strange for a few minutes but I adjust to it very quickly.

There was no reason to believe that I would not be able to adjust to the miss signals that my ears were sending to my brain. All I would need to do was interact with the world for a period of time and my brain would do the rest. But I was in a hurry because I needed to get back to working at full speed and the vertigo had reduced my output significantly. I felt certain that there were a few ways to speed the process up and have a suspicion that my brain had already figured some of them out and was changing my behavior to take advantage of them.

The dizziness wasn’t there all of the time, and it was much less intense at night when I was in bed than during the day. Frankly, I don’t have any idea what dizziness is other than a physical sensation, but the fact that darkness seemed to reduce it is significant. Also significant is the fact that I have never felt dizzy when I have been dreaming. Even the weirdest floating and spinning dreams I have ever had did not have any impact on my sense of orientation. Dizziness then is caused when information from two separate sensory systems doesn’t reveal the same thing. When it’s dark, there is no visual information to conflict with the vestibular information and when I am dreaming, there is no vestibular information to conflict with the visual information. Putting it all together, I started closing my eyes when I felt dizzy and then began to close them before I moved my head too much. This took care of a lot of it. While it felt like I was moving a lot more than I was, I was able to make enough sense out of things to know where I was and where down most likely was.

The next piece of it came automatically, and it was unrelated to my present situation. I do the dishes at home and for some reason, when I’m moving about the sink, I keep one foot on the ground and kind of hook the other foot on the underside of the cupboard. I do this mainly when I need to reach away from the sink and don’t want to take a step. No idea why I do it but it’s a thing that I do, and carried over into other areas of my life. In the case of my vertigo, I found myself doing it even when I wasn’t reaching away. It seemed that I was it doing to to ground myself or to provide more sensory information to my brain to give it something else to work with since it could no longer rely on what was coming from the ear. Once I noticed that the foot information seemed to help, I started to use my hands and elbow to provide more clues. Normally I wouldn’t touch the work table when making panels, but I found that when I placed a free hand on it I instantly felt more certain about the position of my body. If I started to get dizzy when I was walking down a hallway, I would just need to reach out and touch the wall to stabilize things.

There was a certain level of deliberateness to all of these adjustmenta I was making, but it didn’t take very long before I automated doing them. I don’t like being dizzy or the sensation of tumbling when I’m not, so making these feelings evaporate very quickly acts as a strong incentive to reward the actions that eliminate the feeling. In a way, I was powerless to NOT do these things once I discovered that they did something that was positive or eliminated something that was negative.

These work-arounds are very effective, and they made the process of healing from whatever caused the vertigo a lot less challenging or dramatic. Close my eyes or touch something became my reactions to the feeling that I was about to get dizzy.

In a larger way, this whole thing tells a very interesting and important story about how we make sense of the world, deal with ambiguity, and go about adjusting to changes in how we received sensory information or adjust to changes in the quality / accuracy of that information.

First off, it’s just electrical impulses triggered by the stimulation of a sensory cell. The location of that cell, along with the part of the brain that initially receives the signal will determine a lot about the nature of the stimulation, but the brain is not dependent upon the specific signal coming from a specific location in order to make sense of the world. Particularly when it comes to body position. Sure, the first place it will get info from is the vestibular system in the ears. If these sense organs are there and functioning correctly, the information streaming in is very useful and rich. It tells us where down is, and therefore any direction. It tells us that we are moving, accelerating or decelerating, and it gives us an idea of where our head is in relation to any other part of our body that is sending in tactile information. It does this regardless of light condition.

But a lot of this information is available through different modalities. Just because the brain is used to getting it from the ear does not mean that it cannot process visual data to extract the same information. This won’t work in the dark, but when it is bright enough to see something that we are able to place spatially, the brain can take some time to reprocess the information to figure out where we are, what position we are in, and if we are moving. It isn’t perfect – recall any time you were on a stationary train and the train beside you begins to move, or a time when you were on a spinning ride, and everything else is spinning at different speeds – but it works very well under most circumstances. In fact, the brain relies on a combination of the two in order to get a more exact idea of where the body is and what it is doing.

The same applies to the tactile information that the brain is working with. While it isn’t nearly as effective at determining movement or direction, a guess can be made that we are moving when the skin that is facing the same direction begins to send in a signal that corresponds to there being a slight breeze. Orientation can be guessed by two simultaneous touches of something that is stationary because the brain knows where the tactile information is coming from and can compare it to an internal map of where those locations are. Orientation can also be predicted because gravity pulls the skin down, along with all of the tissue and fluids, so the brain is aware of a change in shape and will be able to predict down based on this.

Under normal circumstances, the brain takes it all in and ignores whatever it doesn’t need. Under challenging circumstances, it will do the best with what it has. When one modality is down, it will rely on the information provided by other modalities. And we are free to give it more information any time we like. So long as it is congruent with the interpretation the brain is making, it will be largely ignored. But when there isn’t sufficient information naturally, we can provide more by looking, touching, or hearing.

The opposite it also true. When there is an in-congruence or ambiguity with the sensory information that is flowing in from the senses, we can eliminate it by stopping the data flow from one of the sources. When my ear was telling my brain that I was spinning but my eyes were saying that I was stationary, closing my eyes eliminated the conflict. It went with spinning, which wasn’t a problem because the sensation wasn’t very long lived. There were no crystals to be pulled down and trigger a massive stimulation of the hair cells, so the movement of the fluid that was the result of me turning my head stimulated all of them a little bit. The thickness of the fluid meant that the movement does not continue for very long. As soon as it stopped, my opening eyes would reveal information that was aligned with what the vestibular system was sending.

The worst of the vertigo faded away and hasn’t returned with the exception of a few moments when I haven’t been getting enough sleep or get a little run down. There moments are tough when compared to the day before when I didn’t have vertigo, but they are nothing in comparison to my first experiences with it. In fairness though, I’m not certain that I have ever returned to a vertigo free state. It seems likely that I have, but it is entirely possible that my brain just figured out how to process the sensory information my body generates in a way that allows it to make enough sense of the world to get by. Regardless, I’m grateful for having had the experience because of what adjusting to it forced to learn and figure-out. The human brain is fantastic at adjusting to whatever the world throws at it and adapts automatically and quickly in order to get the needed information from what source can provide it.

Leave a Reply

Your email address will not be published. Required fields are marked *