Moving and Sensing – Using Our Sensory-Motor Cortex
by Teepa Snow, MS, OTR/L, FAOTA
This month’s article is focused on how our brain and body parts work together to allow us to function relatively safely and comfortably once we reach adulthood. There are certainly multiple sections of brain tissue, wiring systems, and body structures that contribute to this complex phenomenon. The brain must take in sensory data and either react to it or respond to it with motor actions and positioning changes, which in turn provides additional data in a somewhat never-ending loop. Our primary drivers of this loop are located in the cortex of the brain. There are some primary strips of nerve tissue and then some associated or helper areas.
Up in the top surface of our brain, in the middle of our cortex, we find two strips of nerve tissue on either side of the brain. These strips are called sensory and motor strips. The strip more toward the back of the brain processes incoming messages and the strip more to the front of the brain sends outgoing messages, so that the body shares with the brain what is being experienced (sensation in) and the brain can tell the body what to do about what is happening to it (movement out). These strips work together, with the help of the cerebellum, cranial nerves, and spinal nerves, so that messages come and go in a reliable, highly complex, and effective, manner. We live our lives using these two systems to function safely and effectively in the world around us.
These strips form the focal area for sensation registration and motoric activation. There is, however, much more to it than that. There are sections of brain in front of and behind the two strips that also contribute to the process and abilities. These broader areas are called the pre-motor cortex and the somatosensory associated cortex. They are part of the frontal and parietal lobes.
These areas take information from the primary sensory and motor strips and interpret it, add in visual data, and add in motor planning. This inter-weaving is really complex and provides alternate ways of getting data processed and handled for emergency reactions, as well as complex planned actions and sequences. For example; pulling your finger back from a sharp sliver of glass when it pricks the surface of your fingertip and then using a broom and a dust pan to clean up the broken glass. Reaction to the prick of the glass shard is reactive and immediate. Actions associated with gathering the supplies and cleaning up the shattered glass are responsive and dependent on pulling together multiple brain areas and functions to allow this motor activity to take place. Additionally, the cerebellum and vestibular system are involved in order to perform this complex task without errors.
In order to appreciate the value of the two strips of nerve tissue on your cortex, I thought looking at a visual representation of what is located where sensation registration-wise and movement control-wise might be helpful. Here is a picture of how the body is represented on the brain. Notice the way the neurons are arranged in groupings that represent different parts of the body. This visual representation is called a homunculus. In Latin, it means little man. The size of the different body parts indicates the amount of brain tissue that is devoted to taking the sensory data from that body part or delivering movement messages to that part.
As in real estate, it is all about location, location, location! Notice that some areas seem enormous while others are hardly present at all when compared to the actual size of the body parts. What this means is that those small body parts on the brain have very few sensory intake receivers while the large images have huge numbers of sensors in very limited spaces. The tongue, lips, tip of the nose, around the eyes, the palmar surface of the hand, the sole of the foot, and genitalia all have huge numbers of sensors. This means that typically you may miss a firm touch to your back or upper arm, ignore the sleeve shifting on your forearm, but immediately react to even the slightest brush of a feather against your palm or a hair across your lip.
Take a look at these two images. Note the difference in the sensory-motor strip of tissue that is present in a mature, healthy adult brain (top version) and the limited amount of living tissue remaining at the end of dementia (bottom image). The majority of the change occurs in the white matter, the wiring. Messages are simply not getting in or out. Typically, there is very limited messaging occurring as the condition advances. The parts of the body that were extremely well represented on the brain still have sensation and some motion, but other parts have almost no awareness and movement is difficult, if even possible.
The brain at the top of the picture is the one that will be able to react to the prick of the shard of glass with both speed and accuracy, as well as take care of the broken glass by sweeping it up and disposing of the debris. The brain in the bottom half of the picture may not even be able to understand where the pain from the shard is coming from, may not be able to pull away, or appreciate that reaching for more of the pieces is dangerous. Instead that person may see the care partner’s efforts to pull their hand away or pull the shard out as dangerous and may strike out to get that person away from them or fall backwards in an effort to escape.
At PAC, we work a good deal with noticing and responding to the existing abilities of the person’s sensory-motor cortex and body. We find that when we use what we have working well, in our brain and body, to support and stimulate nerve activity and neuronal firing, in sensation and movement we can foster what is possible in the changing brain of the person living with dementia. Our guidance and support provide the person living with dementia the opportunity to live more fully, richly, and safely. It turns out that humans do what they can when those around them support their efforts, expand options, offer alternatives, and have positive expectations in responses and attempts to engage. As care providers switch to good looking, textured, plastic glasses, use covered cups and mugs, turn down the maximum temperatures for water heaters and control access to room thermostats and stove controls, life is improved for all concerned.
We can’t change the final outcome of what dementia does to the brain and body. We can, however, change how people living with dementia experience the world and care. How we use visual, verbal, and tactile cues in combination with the possibility of Hand-under-Hand support to match the person’s abilities and missing capacity matters. Making sure the sensation is not overwhelming and the movements are promoted but not too extreme or forceful. Balancing what is most desirable and what is tolerated is essential when creating a living care plan that works.
The goal of this article is not to provide you with everything you could possibly learn about sensation, movement, and the human brain, but rather to provide you with a better appreciation of how vital your role in support and care is for people living with dementia. It is our ability to modify and adapt the use of our bodies and our brains as the other person’s ability systems begin to alter that makes a tremendous difference in perceived abilities and sustained efforts. Doing something for someone is quite different than doing something with someone. When we offer only what is needed to fill in the missing pieces and the gaps, so that together the person is still very much a part of each and every thing that is done. It is what makes life worth living and relationships thrive.
To learn a bit more:
Click here for more information about the motor cortex.
Click here for more information about the sensory cortex.