Sensory Motor Amnesia and Muscle Memory
Most people are familiar with the concept of muscle memory. When we repeat a movement like swinging a golf club over and over, the neurons involved in controlling that movement develop increasingly stronger connections. Existing synapses begin to fire more efficiently, and new synapses are formed as well. As a result, our golf swing becomes more automatic, reliable and forceful the more often we practice.
Despite what the term implies, muscles have no memory of their own—they are controlled by the nervous system. Our nervous system likes to be as efficient as possible, because making fast decisions helps us survive. When our nervous system notices that we keep repeating the same movement or posture, it begins to make that movement or posture automatic. As the muscular pattern becomes more deeply learned, the control and memory of the pattern shifts to different areas of the brain. This process allows the parts of brain responsible for making voluntary decisions to focus on new things which require conscious attention.
The process of acquiring muscle memory is not limited to athletes, nor is it limited to the learning of complex movement patterns like swinging a golf club. The same learning process is going on all the time within your nervous system, every day of your entire life, even if you sit at a desk all day and go home and watch TV at night.
Some people consciously choose to work with their muscle memory, actively training and retraining their muscular patterns in pursuit of a goal. But most of us are unaware that that we are engaged in a constant process of subconsciously reinforcing old movement patterns and learning new ones.
This automatic learning process is innate in all of us, and it serves an important evolutionary purpose. You can imagine how critical muscle memory was to our survival hundreds of thousands of years ago. Back then, only the fit survived, and the ability to move quickly and automatically under stress often meant the difference between life and death.
For most of us today, our survival is not so dependent on being able to move quickly. However, the process of learning and automating muscular patterns is hardwired into our nervous system, so it occurs whether we want it to or not. For the most part, acquiring muscle memory is enormously beneficial, allowing us to move through our daily life efficiently without having to think about mundane tasks like how to brush our teeth or prepare breakfast.
The key to avoiding problems is that we need to be aware of when we are learning muscular habits that might damage our body or lead to chronic pain. Since our nervous system wants to help us be as efficient as possible, it will remember any movement or posture that we choose to repeat—even if the movement or posture is unnatural and could potentially cause pain and damage over time.
Sensory Motor Amnesia
This brings us to the concept of sensory motor amnesia. Thomas Hanna, the man who developed Clinical Somatic Education, coined this term to describe the loss of sensation and motor control that occurs as we learn muscular patterns. As we learn a movement or posture, not only does the control of that movement or posture become automatic and involuntary, but we lose sensation of the movement or posture. Our proprioceptive and vestibular systems gradually adapt so that we are unaware that the muscular pattern is even occurring.
For example, if we sit slouched forward at our computer day after day, our nervous system learns to keep us in that slouched posture by keeping certain muscles contracted, and our proprioceptive and vestibular systems allow us to get more and more comfortable in this unnatural position. Slouching forward begins to feel normal and even good, and sitting up straight takes effort and feels uncomfortable. We typically remain blissfully unaware of this subconscious adaptation until, one day, it finally causes us pain.
So, sensory motor amnesia describes the negative effects of developing muscle memory; the state in which we have lost sensation and voluntary control of a movement or posture because it has become so deeply learned.