Wei Zhang, Ph.D.
时间： 2011-12-16 12:30 - 14:30
地点： 哲学楼 103 房间
The hand: a window to study human movement controlHow does the brain control human movement? This big picture could be captured by using human hand as a tool through a variety of dexterous manual tasks. Thus two topics have been explored in the neural and biomechanical bases of human movement control: 1) motor coordination in a redundant system, and 2) sensorimotor integration responsible to body-environment interaction.
Sub-question 1: How does the central nervous system (CNS) select particular motor patterns from an apparently infinite number of possibilities? This is the famous problem of motor redundancy, also known as the Bernstein problem. For instance, in a pointing task, how does the fingertip adopt its final unique position and trajectory given the availability of eleven kinematic degrees-of-freedom of the upper limb, which is equivalent to solving a system of equations when the number of equations is smaller than the number of unknowns? In order to describe the redundant problem, we applied a recent developed computational tool associated with the uncontrolled manifold hypothesis (UCM) by quantifying the multi-digit coordination during skilled hand actions, which plays a crucial role in everyday tasks such as drinking from a cup, turning a door knob, operating tools, etc. Unlike the traditional view on the redundancy problem, recent studies in UCM framework are based on the principle of abundance, which considers the redundant degrees-of-freedoms as beneficial for flexible behaviors, but not as sources of computational problems.
Sub-question 2: How does the brain integrate sensory information with motor commands for object manipulation? Effective control of object manipulation relies on the ability to adapt kinematic and kinetic outputs by individual digits to the properties of the object (e.g., weight, mass distribution, texture etc.). To initiate the object-hand interaction successfully, the sensory feedback signals (e.g., visual, tactile, proprioception etc.) need to be processed and integrated with the descending motor commands. However, the sensorimotor representations linking object properties to the planning of object manipulation are not well understood. A series of studies have been performed on healthy adults, patients with neuromuscular disorders (e.g., carpel tunnel syndrome (CTS)), as well as with absent of tactile sensation due to digit anesthesia, to investigate: i) the distribution of multiple digit forces as a function of texture, ii) the relation between digit force and position underlying sensorimotor learning process, iii) sensorimotor memory transfer of learned manipulation to a new object property, iv) changes in sensorimotor integration mechanisms that result from peripheral neuropathy, and v) interaction of sensory feedback signals (e.g., vision and tactile inputs) in motor planning and learning. These studies will contribute to a better understanding on the physiological mechanism of hand control and lead to better techniques to alleviate problems due to aging or neurological disorders.
2011-12-16
2011-12-16