Evaluating How the Nervous System Coordinates Voluntary Movement in the Arm

In motor nervous system disorders, such as stroke, the CNS is unable to coordinate normal
voluntary movement. This is often caused by malfunctioning proprioception. Proprioception is
one's sense of the relative position of neighboring body parts. It allows an individual to
feel the orientation of one body part to another. It also provides information about the
rate and direction of movement so that an individual can change muscle contraction
immediately as incoming information about external forces is received. The two main
components of proprioception include sensory nerve cells located in the inner ear and
stretch receptors located in muscles, skin, tendons, and joint-supporting ligaments. The
purpose of this study is to determine how proprioception is communicated from the stretch
receptors in skin, joints, and muscles to the CNS. Specifically, the study will compare the
differing roles of agonists, muscles that cause movement, versus antagonists, muscles that
oppose agonists, in proprioception.

Participants will be assigned to one of seven substudy groups. Each group will partake in
one or more study experiments, which will each take 1 to 4 hours. Participants enrolled in
more than one experiment will report to the study site on separate days. For each
experiment, the participant will sit at a table with a specialized device, called a
manipulandum, which has motorized elbow, wrist, and finger manipulators to control the
movement and position of a participant's arm. Depending on the experiment, several forms of
joint rotation and arm movement will be carried out by either the participant or the
manipulandum. Electrical activity of certain muscles and nerves will be recorded in all
experiments by various kinds of electrodes. A tendon vibrator will be used in some
experiments to activate muscle receptors that signal to what extent and how fast a muscle is
contracting or stretching. Regional anesthesia will also be used in some experiments to
reduce sensory input from the skin and joints. Participants will receive follow-up phone
calls after an experiment to check for any side effects from procedures.

Exclusion Criteria for Anesthesia:

- Known neuromuscular abnormalities

- Known allergies or hypersensitivity to anesthetics

- Blood clotting or bleeding disorder

- Use of anticoagulants

- Psychologically inappropriate behavior (e.g., apprehension, uncertainty with
procedure)

- Significant history of any cardiovascular problem

Exclusion Criteria for Nerve Recording by Electrode:

- Significant history of fainting or problems with blood pressure control