October 19, 1922 - September 20, 2008
The broad objective of my research over the years, has been to identify and analyze how the nervous system controls muscle activity in the intact behaving animal including human subjects. Much of my experimental work has been concerned with the neural regulation of the respiratory muscles. My major contribution in this area was defining the neural pathways of the reflex circuits which control the expiratory activity of the abdominal muscles, the major expiratory muscles in vertebrates. Work in this area is still going on. Two avenues of current work are: 1) determining whether rat is as adequate a model as the cat and 2) characterizing the abdominal expiratory reflex in human subjects. If the rat proves to have the expiratory reflex we shall use pharmacological agents to identify which category of pulmonary vagal receptors provides the critical feedback for initiating and supporting active expiration.
Another area of investigation is that concerned with the motor control of mastication. Like respiration, chewing is quite an automatic motor behavior which is thought to be under the control of central pattern generators. Our goal has been to define the output of the central pattern generators when we deliberately control sensory feedback from the periphery. In early experiments we provided our healthy adult subjects with gum of different hardness to chew. (The Wm. Wrigley Co., generously provided us with the tasteless gum bases of different hardness. Without this item our experiments would not have been possible). By analyzing both jaw movements and masticatory muscle activity on a cycle by cycle basis, we deduced how the nervous system processes the sensory feedback to generate the efferent pattern of neural activity. By comparing records obtained when the subject's attention was distracted from the act of chewing with those obtained when the subject paid attention to each chewing cycle and voluntarily controlled the cycle duration. Descending pathways which control voluntary jaw movements by pass the central pattern generators, which are thought to regulate the chewing frequency of automatic chewing. We also analyzed on a cycle by cycle basis the chewing activity in individuals complaining from temporal mandibular joint syndrome, suffering motor dysfunctions due to stroke, cerebellar disease or Parkinson's disease.
Currently we are using single motor unit analysis to assess the output of the "chewing center," and the central respiratory neurons. Our goal is to understand how the central nervous system integrates sensory feedback during chewing, breathing and speaking. We expect that by comparing the behavior of single motor units during a variety of motor activities we shall gain insights about the neural control of laryngeal, thoracic, abdominal and masticatory structures.