Submovements composition and quality assessment of reaching movements in subjects with Parkinson's Disease

The segmentation of seemingly continuous movements into segments has been theorized for many years. These segments may be considered as 'primitive' movements, or building blocks of more complex movements. The existence of these fragments, or sub-movements as they are called, has been supported by a wide range of studies over the past 100 years. Evidence for the existence of discrete sub-movements underlying continuous human movement has motivated many attempts to 'extract' them. Recently, the sub-movement theory gained a great appeal in the rehabilitation field. In fact, understanding movement deficits following CNS lesions, and the relationships between these deficits and functional ability, is fundamental to the development of successful rehabilitation therapies. So, here a novel sub-movements decomposition method is proposed; it is based on a constrained-Expectation-Maximization. This representation allowed us to explore whether the movements are built up of elementary kinematic units by decomposing each signal into a weighted combination of 2D Gaussian functions. These can be used to assess the quality of reaching movements in subjects with Parkinson's Disease.