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Living History of Physiology
 Beverly
Bishop
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.
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