Motor Movement Controversy

Motor movement development has been a topic of controversy for the last century. The feud began in 1906 when Sir Charles Sherrington published The Integrative Action of the Nervous System. The work summarizes over two decades of research, revealing many fundamentals of neural science for the very first time (Burke, 2007). He was not only the first to suggest that the nervous system was a complex network of separate neurons, coining the term ‘synapse’, but he also was the first to discuss reflex arcs in detail. Although his work is noted for its advances in the field, some of Sherrington’s ideas were far-fetched; including his belief that complex behavior could be explained through the combination of individual reflex actions intertwined (Sherrington,

Bernstein argued that a reactive theory, such as the reflex theory, would only be plausible in a static environment. He was one of the first to analyze the body as a biomechanical being, exploring neural pathways, circuity, and neurosensorimotor mechanisms to explain behavior (Masgutova, 2016). Coordination of movement was one of his most fundamental concepts. He declared that movement is a complex behavior with many degrees of freedom. A single movement involves the precision between a large amount of biological components such as the brain, neurons, synapses, muscles, and bones. Coordination of all these mechanisms, Bernstein argued, would rapidly overwhelm the conscious mind (Bernstein, 1996). In an attempt to address this issue, Jackson shortly published his work on the hierarchical theory. The hierarchical theory suggests the brain has evolutionary levels, with the higher levels suppressing the function of lower ones. The lower levels repress the body directly, including the anterior spinal horns and the containing cranial motor neurons. The middle level included the motor cortex and basal ganglia, and the highest level was composed of the premotor frontal cortex. He suggested that patients with higher brain damage would encounter two types of symptoms, positive and

Positive symptoms are the emergence of function of lower brain centers and negative are the malfunction or lack of higher brain centers (Trimble, 2007). However, the original hierarchical theory has a major limitation; it does not explain dominance of reflex behavior. For example, accidently touching a hot surface causes an immediate withdrawal of the hand. In this example, the lower brain center in controlling the upper in a “bottom up” fashion, contrary to Jackson’s hypothesized “top down” hierarchical action. More contemporary theories, have abandoned the strict hierarchal organization that Jackson suggested, but still acknowledge that the nervous system is a conditional hierarchal system (Shunway-Cook, 2007). Modern texts similarly describe the motor system with the spinal cord identified as the lowest level, followed by the brain stem, and cortex as the highest. However, they also discuss the importance of the inhibitory effects of basal ganglia and the excitatory effects of the cerebellum (Kandel, et al.,