I highly recommend that everyone study a little basic neuroanatomy. You’ll be amazed at how much insight it gives you, not only into how the brain works but how your mind and emotions work and into the experiences you have every day that you normally take for granted.
For example, did you know that only a small percentage of the input from your senses makes it into the brain? Most input from the body, eyes and ears is discarded. It’s the job of the thalamus to prioritize this input and decide what gets through. Here’s an illustration of the Thalamus:
You can see that it is at the top of the spinal cord where it receives the sensory signals from the body. In addition it receives signals from the retina in the eyes and the cochlea in the ears. It then decides what to do with these signals and selectively sends them on to the relevant brain areas. Signals from the eyes, for example, are sent on to the visual cortex, which is at the back of the brain. Smell is the only sense that is routed directly into the brain, bypassing the thalamus. Some speculate that this is why smells are so powerful at evoking emotional responses and triggering memories.
But, getting back to how the thalamus regulates sensory input, have you ever wondered how it is that you automatically turn to see what’s happening when you hear a siren or a baby cry? It’s the thalamus that is involved in deciding that this kind of sound needs immediate attention.
How is this relevant to mental health?
One theory about what goes wrong in various mental health conditions is that there is a problem with the thalamus in that it either doesn’t pass enough information on to the brain or it lets in too much. The thalamus provides a so-called ‘stimulus barrier’ which, in this case, does not work normally.
Now, this is my own hypothesis, based on my own observation of my own internal experience with my condition.
This is a bit difficult to explain. To try to understand how this works let’s try a little math. As stated above, the thalamus only passes a small portion of the signals entering into it on to the brain for further processing. So, let’s start with the total 100% of the signals coming in through the senses and lets say that a normally functioning thalamus discards 95% of those signals, passing the remainder on to the brain. So, the brain normally receives only 5% of the total input. That 5% is what the brain normally processes.
Now, let’s say that the thalamus is not working quite right and discards 96% of the input instead of 95%. That’s only a 1% difference and may not seem like it would make much of a difference. But, how does this affect the amount of information passed on to the brain? Now, instead of receiving 5% of the total input, it’s only receiving 4%. That’s not 1% less, but 20% less than the brain normally receives. Conversely, if the thalamus discards 94% of the input instead of 95%, that’s only a 1% difference in the stimulus barrier but the brain now receives 6% of the total input instead of 5% or 20% *more* information than normal.
The point is that small changes in the stimulus barrier make much larger differences in what the brain receives and has to process.
This may explain what happens in some mental health conditions. A large body of experiments has shown, for example, that the brain doesn’t deal well with having inadequate stimulation. In sensory deprivation experiments, people soon begin even to hallucinate, as if the brain is making things up to compensate for being starved for external stimulation.
And what if there is too much stimulation?
Maybe this accounts for what I experience much of the time. I am hypersensitive to my environment. I notice every sound. I have a low tolerance for disorder and clutter. My office is painted in forest green because light colored walls are ‘too bright’. I generally keep light levels low. Going outside is generally overwhelming. Just too much stimulus. A short walk around the block is usually all I can take. I prefer overcast days and night time to daylight. Shopping is exhausting. When I try to go to sleep at night, the opaque blinds have to be pulled but even the small amount of light leaking in around the edges is too much. So, I have a pair of motorcycle goggles that I have blacked out to give me total darkness. I can hear Gail’s every breath. Sometimes I have to wear ear plugs to be able to sleep.
Sometimes even during the day, it gets to be too much. I have another pair of motorcycle goggles with lenses that have the same prescription as my normal glasses. They block my peripheral vision, reducing stimulation, and sometimes putting them on is like taking a tranquilizer. I pull the blinds in my office. I close the door. Sometimes music is helpful. But, sometimes during the day, I get so overstimulated, despite the countermeasures, that I have to go into the bedroom, turn out the lights, put on the goggles, put the ear plugs in, and just lay there in the dark and the quiet until the overstimulation subsides.
Ritalin helps sometimes too. After the 20 or 30 minutes that it takes to take effect and for the couple of hours that it’s effective, I am much calmer. The overstimulation subsides and I can function more or less normally. This isn’t what you might expect from a medication that is actually a stimulant. In fact, it’s chemically similar to cocaine! This is characteristic of the ‘atypical response to stimulants’ that some people like me have who have AD(H)D. One therapist told me that when a client reports that cocaine calms them down, they screen them for AD(H)D and their response to medication like Ritalin. It’s hypothesized that sometimes people use drugs like cocaine to ‘self-medicate’.
This leads me to hypothesize that Ritalin is affecting the stimulus barrier. Ritalin *is* a stimulant, but the brain works in complex ways. Maybe Ritalin is stimulating it in a way that adjusts the thalamus so that it discards a little more input than it otherwise would. So, by nature of how the stimulus barrier works, my brain is getting significantly less input and so it doesn’t have to work so hard just to do it’s normal job.
In this way, Ritalin, rather than inducing a ‘high’, induces a ‘normal’.
It’s a hypothesis that I need to research further …