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INFORMATION SHEET FOR VOLUNTEERS
REFLEX CONTROL OF THE HUMAN MUSCLES

Background to the laboratory: This laboratory investigates the control of human muscles.  Muscles are controlled by two fundamental mechanisms: (1) the central pattern generator (CPG) that sets the pattern of contraction by sending electrical impulses to muscles; and (2) the peripheral control that modulates the output of the CPG. The peripheral modulation of the CPG ensures that optimum forces are developed. The peripheral control mechanisms originate from the receptors within the skin and muscles.  These receptors monitor contraction forces and modify the activity of muscles in order to facilitate movement of the limb and prevent damage to tissues. To investigate their connections to motoneurons (the nerves that innervate muscles), we stimulate these receptors electrically and/or mechanically in consenting adult volunteers. The responses of the muscles to the stimulus are recorded using intramuscular fine wire and surface electrodes. These studies contribute to a better understanding of the neuronal circuitry of the neuromuscular system. 

Significance of the experiments:  Movement is one of the most fundamental functions of humans. Despite its fundamental importance, the neurological mechanisms that control movement are not yet understood.  Once these mechanisms are well understood, they can be used for the diagnosis and treatment of muscle / joint disorders, fatigue, and tremor. 

EXPERIMENTAL PROTOCOL:  You will be asked to take part in one of the four experiments that are taking place in the laboratory at present. 
Jaw experiments; Leg experiments; Hand experiments
Jaw experiments:  In these experiments you will be asked to bite on bite bars.  Your teeth, skin or oral mucosa will be stimulated using mechanical and/or electrical stimuli.  The mechanical stimulus is applied via a probe attached to a vibrator, and the electrical stimulus is delivered using intramuscular or surface electrodes.  The electrical activity of your jaw muscles is recorded using surface and intramuscular electrodes. In experiments where mechanical tooth stimulation is used, local anaesthetic block is applied around the stimulated tooth to study the dispersion of the stimulus to neighbouring tissues.  Once the static part of the experiment has finished the dynamic part will be initiated.  The participant will open or close his/her mouth while the bite bars either do not resist the action (simulation of simple jaw movement) or resist the movement with a defined force (simulating biting on a piece of food).  In other experiments, the lower bite bar will occasionally apply very small and defined opening or closing perturbations to the lower jaw so that the stretch or unloading reflex can be studied.
Leg experiments: In these experiments you will be asked to push against a transducer (foot plate) with your foot.  One or two of your leg muscles will then be stimulated using mechanical and/or electrical means.  While mechanical stimulus is applied via a probe attached to a vibrator, electrical stimulus is delivered using surface electrodes.  The electrical activity of your leg muscles will be recorded using surface and intramuscular electrodes.
Hand experiments In these experiments you will be asked to move your index finger slightly so that one of the muscles that move your finger is activated.  We would then apply laser, electrical or magnetic brain stimulation while you are moving your finger. 
General procedures that applies to all experiments: