How humans move: the neural origins of rhythmic and discrete movements.

• Online Access: http://hdl.handle.net/2047/D20248890

Humans have a wide behavioral repertoire ranging from locomotion, object-manipulation, communication, and much more. From the mundane to amazing bodily feats, the nervous system is responsible for controlling movement at all levels. In this literature thesis, the main purpose is to bring together and discuss scientific literature on the control mechanisms of the human movement system, specifically how rhythmic and discrete movements are controlled. Rhythmic movements are defined by being cyclical and periodic, while discrete movements are one-time movements with a well-defined beginning and end (Sternad and Hogan 2004). This type of definition focuses on the external factors of the movement, but misses the internal mechanisms responsible for achieving it. In order to address this and approach the movement system from a more comprehensive viewpoint, this review paper will examine rhythmic and discrete movements using an integrative approach from both a behavioral and physiological perspective. The behavioral approach will cover topics on degrees of freedom, synergies in the human motor system, as well as the context with which rhythmic and discrete movements are performed. The physiological approach will start with an overview of the anatomy of the motor cortex, supplemental areas of the motor system, and how these areas function together. Next, we discuss the descending and ascending corticospinal tracts and the involvement of the brainstem during rhythmic and discrete movements. We will also discuss two original studies with pilot data on the stimulation of the motor cortex and the posterior parietal cortex. Finally, this review concludes with an overall perspective on how rhythmic and discrete control mechanisms are different and what role they play in human movement as a whole.