A Wobbler’s Story

This is the blog post I promised about the woman who lost her sense of balance & then recovered it. This is one of my most favorite case studies. It is remarkable in what it demonstrates in our resilience.

Cheryl always feels like she is falling. There is never a moment in her life that she does not experience the sensation of falling. When she is lying flat in bed, she feels as if she is falling. When she is sitting in a chair, she feels as if she is falling. When she stands, she feels as if she is falling. And when she falls and is lying in a heap on the ground, she still feels like she is falling.

Not only does she constantly have the sensation of falling, but when she moves, everything moves. She describes it as eve

Vestibular System

Inner ear, showing semi-circular canals Image via Wikipedia

rything seeming to be made of Jell-O or being wiggly. Moving objects seem to bounce. Rooms spin.

She can not be still because she is constantly trying to catch her balance. Walking is nearly impossible. Standing more so.

Cheryl lost her sense of balance when she was given the antibiotic gentamicin for a post-operative infection.  Gentamicin is cheap & effective, but when taken for too long of a period of time, it will destroy the inner ear causing hearing loss, ringing in the ears, & a loss of balance

. Cheryl can still hear, but she has ringing in her ears & no sense of balance. She was 39 years old. People who suffer a loss of balance due to gentamicin call themselves Wobblers.

Balance relies on two separate sets of inputs. First are the signals that come from our semicircular canals. These tell us which way is up and how badly we’ve gotten off of perpendicular. They are responsible for that lingering disquieting spinning sensation after having been spun around.Cheryl’s semi-circular canals were destroyed by the gentamicin.

The second source of balance information is from the eyes. When we can see the horizon and other horizontal lines, we can tell if we’re upright or not. Motion sickness comes from this source. Oddly, Cheryl’s visual support for her balance is easily disturbed by looking at zig-zagging lines or other designs that are not square or imitate depth. Consequently, Cheryl is constantly fatigued. Her brain is working overtime to keep her relatively balanced taking away resources used for calculating, reasoning, or even communicating.

Luckily, Cheryl found out about a neuroplastician named, Paul Bach-y-Rita. He had developed ways of retraining the brain to use other cortical areas to compensate for deficits. His has helped people who have had strokes, accidents, and birth defects. And, he had a

Paul Bach-y-Rita (1934 - 2006)

possible solution for Cheryl.

His idea was to help her bypass the semi-circular canals & the cortical area that interpreted their input. He realized that she probably was still getting signals from the canals, but that it was “noisy” filled with bad information and perhaps some good information. The problem was that the brain didn’t know which was which, & then when she tried to match her faulty information from her semi-circular canals up with the accurate information from her eyes, her brain didn’t know which to believe. So, Bach-y-Rita created a helmet that was lined with sensors. These sensors would detect the position of her head. He fed this information into a small thin device that she would press to her tongue. It was covered with electrodes. When her head tilted one way, that area on her tongue with tingle with gentle electrical energy. When it tilted another, her tongue would tingle in another place. In this way, her brain could start to learn which signals were accurate and which were not, & then begin to match up the accurate information and ignore the inaccurate.

It took her only a couple of hours to get the hang of it. She was able to maintain her balance while the helmet was on her head & the tongue tingler was in her mouth. She was even able to maintain her balance for a few minutes afterward. So, she began to wear it for a couple of hours everyday, & the length of time that she could maintain her balance increased… exponentially. It soon began to stretch into days.

They sent her home with the device. She wore it whenever the effect began to wear off, & soon it lasted weeks. Then, it was months. Now, she hasn’t needed it for years. In essence, she was cured. Her brain had adapted to her new sensory input for balance! It was a miracle.

A tongue sensor that is similar to the one Cheryl wore.

An apparatus similar to the one Cheryl used

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Week 4 (7 – 11 Nov): From Stimulus 2 Perception

As I study the material in the textbook & read from other sources I continue to marvel at the lack of clarity between the four basic steps in process of transforming stimuli to perceptions:

Stimulus –> Transduction –> Sensation –> Perception

Stimulus is easy, right? That is the energy & substances & objects in our environment that we encounter and that match up with the receptor cells in our sense organs. Stimuli clear exist in the environment and outside of our nervous system.

Transduction, on the other hand, is where things get murky, but only just. Transduction, we are told, occurs when the receptor cells transform the stimuli into neural impulses. Again, it takes place in our sense organs, but outside of our nervous system… or does it? It ends with the firing of the nerve cell that is designed to be stimulated by the stimulus.

Sensation, though, is definitely steeped in murkiness. The textbook defines sensation as “the process by which stimulation of a sensory receptor produces neural impulses that the brain interprets…” But isn’t the production of a nerve impulse from transduction? When is the nerve impulse part of transduction and when is it part of sensation. The boundary is not clear to me. Are the receptor cells transducers of stimuli or are they sensors of stimuli? Is this just semantics? Will it make a difference on the AP exam?

Perception is definitely the murkiest! Perception is the process of making sensory patterns meaningful. That sounds pretty straightforward, right? I mean we interpret the patterns in the brain, but we’ve completed the brain unit so we can ask where in the brain is the boundary between sensation & perception. Aaah! MURK! Is the thalamus, that great relay station of sensory input, part of sensation or is it perception? Is the initial evaluation in the cerebral cortex sensation or perception. Is it only when other parts of the association cortex are involved that it becomes perception?

I’m definitely more comfortable when these things are clearly defined and delineated. Perhaps one reason there is this excessive amount of murk in this area is that psychologists & neurologists and their endless variations and allied fields are not yet sure.