Neural circuits for movement
The main focus of our lab is to learn how the neural circuits that control movement are organized and how they function.
Neural circuits controlling movement can be sub-divided into four categories:
- Intention and selection circuits – those within and between higher centres, including the cortex and basal ganglia and their outputs
- Command circuits – those between the brainstem and spinal cord
- Organization circuits – those within the spinal cord that ensure coordinated motor activity
- Action circuits – those between the spinal cord and the muscles.
Our work on intention circuits focuses primarily on recordings from the human basal ganglia during deep brain stimulation surgery for movement disorders. As part of the surgery, we study the properties of basal ganglia neurons and their responses to stimulation.
Studies on the other three circuits take place in the laboratory, where we use transgenic mice to identify and characterise neural circuits using molecular biology, anatomical, and physiological techniques.
Our work on command circuits, supported by a grant from the CIHR, focuses on genetically identified neurons in the brainstem that may be involved in processing motor commands from higher centres to send to the spinal cord. It is important to understand the identity and properties of these neurons, as commands will be poor in neurologic diseases such as Parkinson’s disease, and interrupted in injuries such as spinal cord injury.
Our work on the organization circuits in the spinal cord, also supported by CIHR, focuses on circuits responsible for producing the coordinated activity of locomotion. We are also studying circuits important for basic hand function – grasp.
Our work on action circuits has identified a mechanism by which the spinal cord controls the response properties of motoneurons to ensure the degree of muscle contraction is appropriate for the intended behaviour. In addition, we are studying how motoneurons use their complex structure to appropriately process the commands they receive from other neurons. This work is also supported by CIHR.
In a long-standing collaboration with Dr. Victor Rafuse, we have been studying motoneurons that we derive from embryonic stem cells. We are using these cells to study the development of particular motoneuron properties, and are exploring the use of these cells for transplantation – for example, as a therapy for peripheral nerve injury.