Greg T. Gdowski
- Ph.D., Boston University, 1996
- Biomedical Engineering
- Center for Navigation and Communication Sciences
- Center for Medical Technology & Innovation
Moving within our environment is a basic function essential to every day life. Although movements can be considered simple changes in position of some body part, each movement is produced and controlled differently by the central nervous system depending upon the context. Movements are commonly classified as either voluntary or reflexive, yet almost every movement has both components. Even walking involves the coordination of reflexive head movements that are necessary to stabilize the visual scene on the retina and voluntary limb movements. The overall goal of my research is to elucidate how sensory signals, in particular those of the vestibular system, are used in the control and coordination of reflexive and voluntary movements.A main focus of my research is the study of reflexes that reorient the head with respect to the body (vestibulo-collic reflexes, VCR). These likely assist in the prevention of whiplash injuries, which annually affect over 1 million lives in the U.S. alone. The neurons in the vestibular nuclei thought to mediate these reflexes are confronted with two intriguing problems that arise because the vestibular sensory epithelium, located in the head, can move because of a multi-articulated neck.
- How do neurons of the vestibular nuclei distinguish between sensory inputs produced as a consequence of self-generated/voluntary head movements and passive whole body movements?
- How do neurons of the vestibular nuclei control muscles that operate in different coordinate systems when the primary sensory signals they receive are in head coordinates?
Previous research suggests that both of these intriguing problems are possibly resolved, in part, by neurons located in the vestibular nuclei that receive direct primary input from the vestibular nerve (J Neurophys. 81: 416-428, 1999; J Neurophys., 81: 436-449, 1999.). We are now studying how neck muscle activity relates to the vestibular signals carried by vestibulospinal neurons in the vestibular nuclei during a wide variety of voluntary and reflexive head movements. Some of the questions we're asking are:
- Are angular and linear acceleration signals combined linearly by vestibulospinal neurons?
- Are vestibular signals carried by vestibulospinal neurons modified during the execution of the vestibulo-collic reflex that produces pitch head movements?
- How are angular and linear acceleration signals plastically adapted within the vestibular nuclei to maintain performance following selective Labyrinthine lesions of the vestibular endorgans?
To answer these questions single extracellular potentials from neurons are recorded simultaneously with EMG recordings in awake behaving monkeys in order to assess relationships between neural signals and muscular activity. Microstimulation techniques are employed to identify neurons receiving direct input from the vestibular nerve that project to the spinal cord.