Graduate Studies Faculty
Alfred L. Nuttall, Ph.D.
Research Interests:Physiology and pathophysiology of the cochlea. Microvascular physiology. Hair cell physiology and cell biology Mechanisms of sound injury to the cochlea; molecular » Click here for more about Dr. Nuttall's research » PubMed Listing
Preceptor RotationsDr. Nuttall has not indicated availability for preceptor rotations at this time.
Faculty MentorshipDr. Nuttall has not indicated availability as a mentor at this time.
Summary of Current Research
The work of the cochlear physiology laboratory is divided into two major areas; 1) mechanical processing of acoustic energy and function of the sensory cells, 2) the control of inner ear blood flow and the pathophysiology of cochlear blood circulation. In both areas, measurement of physiological variables is accomplished with the use of state of the art approaches. For example, laser interferometry is used to determine the motion of cellular structures in the organ of hearing, the organ of Corti, and ‘intravital microscopy’ is used to make direct observations of blood flowing in capillaries within the cochlea.
The broad goal of this work is to understand the electro-mechanical processing of acoustic energy by the cells of the organ of Corti. This process consists of the transduction of the sound stimulated vibration of the organ through movement of stereocilia of hair cells. This movement gates a mechano-sensitive channel. One type of hair cell, the outer hair cell, has a voltage-sensitive motor capable of changing cell mechanical properties at great speed. These properties of hair cells set the stage for what is thought to be a feedback amplifier of the acoustic stimulus.
Current studies are concerned with the nature of the feedback amplifier, called the cochlear amplifier. Does the amplifier add power to the incoming acoustic energy? Does it cause a change in the mechanical properties of the organ of Corti such as its mechanical stiffness? Moreover, the outer hair cells are innervated by efferent fibers which have an inhibitory influence on the organ of Corti function. The physiology of this efferent control is also a focus of this work.
Loud sound causes a temporary desensitization of the organ of Corti before inducing permanent damage. The pathophysiology of sound is studied by measurements of the dynamic changes in the electrical and mechanical properties of the organ. Pharmacological approaches are used to manipulate hair cells in combination with sound.
Cochlear Blood Flow
The broad goal of these studies is to learn the roles of inner ear blood flow in normal cochlear function (homeostatis) and pathological conditions such as loud sound induced damage. The blood flow to the inner ear is supplied by a single end artery, the spiral modiolar artery. This small artery has various mechanisms of vasoconstriction and dilation. Neurogenic control of the vessel is generally from sympathetic fibers, but multiple neurotransmitters are involved.
Studies are being carried out to characterize the active ionic channels of vascular smooth muscle from the spiral modiolar artery. Whole cell recordings are made from segments of the isolated artery. The channel parameters of smooth muscle are determined by perfusions of channel blockers and neurotransmitters. The vessel is transmurally stimulated by electric current to result in excitatory junction potentials and the transmitter properties are determined.
Intravital microscopy is a method that allows direct observation of capillary flow, i.e. red blood cell motion and vessel diameters. These observations can be made on the highly vascular tissue, the stria vascularis, responsible for establishing the ionic balance and electrogenic potential of the endolymph. The capillary-based control of flow and vascular permeability of the capillaries are being studied as a pathological mechanisms of age and noise induced hearing loss.
- B.S. (Electrical Engineering), Lowell Technological Institute, 1965
- M.S. (Electrical Engineering), University of Michigan, 1968
- Ph.D. (Bioengineering), University of Michigan, 1972