Movement that has the appearance of a sequence of individual events but that the brain processes as a single but collective event. Clusters of neurons receive simultaneous signals from the basal ganglia, which they then pass on to clusters of neurons in the motor cortex. Because patterns are faster and easier to learn and to repeat than individual events, the brain can initiate and control movement with great efficiency. Patterned movements make use of the extrapyra-midal system, which includes brain structures such as the basal ganglia and area of the brainstem and nerve pathways that control movement. Any damage to the extrapyramidal system affects the body’s ability to carry out patterned movements. The cerebellum, the brain’s coordination center, also is critical for patterned movements. Most movements of the lower extremities, such as walking, are patterned movements.
Scientists believe that the brain “maps” certain neuron clusters for specific patterns. These same clusters always handle the same patterns. When the brain learns new patterns, such as when a person takes up a new physical activity, the brain shifts its mapping to include additional clusters to handle related patterns. People who use muscle groups in specialized and refined ways such as athletes, musicians, and dancers refer to this as “muscle memory” the muscle groups involved function as though they automatically engage in the movements of, for example, a diving position or a complex musical scale. The movements remain voluntary, of course, but occur with such efficiency that they appear to require no conscious thought.
The brain appears to have a broad ability to learn new patterned movements and a more limited context for reassigning previously learned ones. Relearning typically becomes necessary when areas of the brain become damaged. Part of the neuron cluster may remain functional but cannot handle the entire task, or there are not enough healthy specialized neurons, such as those that direct movement, available to accept large patterns (like walking). In Parkinson’s disease, the damage is dynamic, ever extending as the disease process progresses. Patterned movements such as those of walking are incredibly complex despite the efficiency of clustering their multitude of sequential and simultaneous actions and reactions. All neurons in the cluster must carry out their assignments to allow the pattern to be executed properly. As neurons within pattern zones die, pieces of the pattern fall out. Signals become chaotic and confused, movements disrupted.
Understanding of patterned movements has led to successful rehabilitative strategies for brain dysfunction in which the damage is fixed, such as after injury due to trauma or stroke, or in conditions such as cerebral palsy. The extent to which disturbance of patterned movements matters in Parkinson’s disease is unclear, however, as the more significant factor is the progressive loss of dopamin-Ergic neurons. The loss thwarts any attempts the brain may make to remap neuron clusters.