Most of the experiments in my laboratory involve recordings made directly from the brains of experimental animals during behavior. In these experiments, we are able to study not only the intricate circuits comprising real networks of nerves and neurons, but also the signals produced by individual neurons during movement. Much of this work is done in collaboration with students and faculty from the Biomedical Engineering Department and the Institute for Neuroscience (NUIN). The three fundamental goals of my research are the following:

To understand the nature of the brain's own signals -- the "language" in which movement command signals are expressed by neurons in the central nervous system.

To understand the mechanisms by which these signals are produced -- the nature of the connections among networks of neurons, and the transformations that occur in the signals as they propagate throughout these networks.

To develop applications of these basic principles that could be of therapeutic value to human patients.

Choose a project below to learn more.

Projects

The foundation of our work has been for many years, the study of the brain's representation of reaching and grasping movements. Begun using single electrodes in several brainstem areas, the cerebellum, and the motor cortex, it has evolved in the past decade to the use of multi-electrode arrays, chronically implanted in the primary and premotor cortices. We are interested in the relation of this activity to muscle activation, forces, and movement, how the cortical activity is affected by context, how it changes during learning, and how networks of neurons interact to generate the signals underlying movement.

Using multi-electrode array technology and the basic principles we and other labs have discerned through basic research, we are working to develop neural interfaces that allow us to read out detailed information about arm movements from the motor cortex. These so called, "brain machine interfaces" provide a remarkable new tool for studying the brain, and are even capable of restoring movement to paralyzed individuals. We have developed a unique BMI that uses "functional electrical stimulation" to cause paralyzed muscles to contract. With this BMI we have restored voluntary grasp to monkeys during transient paralysis of the hand. We are developing a similar system to restore locomotion to rats with spinal cord injury.

Although poorly understood and scarcely even appreciated as a real sense, "proprioception", the innate sense of limb positon and movement, is a critical component of our ability to make normal movements. In parallel with our studies of the basic properties of the motor system, we study proprioception using microelectrodes implanted in two different areas of the primary somatosensory cortex, and even in the cuneate nucleus at the very base of the brainstem. Through these recordings and associated modeling studies, we are working to understand how signals from the muscles' length and force sensors are combined and transformed into information about hand position.

Paralysis, the devastating inability to move arms or legs, is the most obvious consequence of severe spinal cord injury. However, SCI also causes a loss of sensation from the limbs, typically affecting both the sense of touch and proprioception. Studies have revealed that this loss of somatosensation (the "sense of the body") in the very unusual cases when normal strength is preserved, makes standing, walking, and normal arm movements almost impossible. In parallel with our development of "motor" BMIs, we are also developing a somatosensory BMI. Instead of using cortical recordings to read information from the brain, we are using intracortical microstimulation to write information to the brain, causing an artificial sense of limb movement.