Neurophysiology

(redirected from neurophysiologists)
Also found in: Dictionary, Thesaurus, Medical.
Related to neurophysiologists: intraoperative neurophysiological monitoring

neurophysiology

[¦nu̇r·ō‚fiz·ē′äl·ə·jē]
(neuroscience)
The study of the functions of the nervous system.

Neurophysiology

 

the branch of physiology that studies the functions of the nervous system. Together with the morphological disciplines, neurophysiology constitutes the theoretical basis of neurology.

Although ideas regarding the reflex principle of nervous system functioning were advanced in the 17th century by R. Descartes and in the 18th century by J. Prochaska, neurophysiology did not begin developing as a science until the first half of the 19th century, when experimental methods were first used to study the nervous system. The development of neurophysiology was aided by the accumulation of anatomical and histological data on the structure of the nervous system, for example, the discovery of the nervous system’s structural unit—the nerve cell, or neuron. Also of great significance was the development of a method for tracing nerve pathways that was based on the degeneration of nerve fibers as they are cut from the neuron’s cell body. Early in the 19th century, C. Bell (1811) and F. Magendie (1822) independently discovered that transection of posterior spinal roots results in a loss of sensitivity, while transection of the anterior roots results in a loss of motor ability; this is evidence that the posterior roots transmit nerve impulses to the brain and the anterior roots transmit them from the brain. Extensive use was made thereafter of transection, destruction, and artificial stimulation of various brain structures to locate the different bodily functions in the nervous system.

An important stage in the development of neurophysiology was reached with I. M. Sechenov’s discovery of central inhibition in 1863; this is the phenomenon that arises when stimulation of certain centers of the nervous system (Sechenov’s nuclei) does not result in excitation but in suppression of activity in those centers. The interaction of excitation and inhibition was subsequently found to underlie all types of nervous activity. Detailed information was obtained in the second half of the 19th century and in the early 20th on the functional role of the various divisions of the nervous system and on the main patterns of reflex activity in each division.

N. E. Vvedenskii, V. M. Bekhterev, and C. Sherrington made major contributions to the study of function in the central nervous system (CNS). The role of the brainstem, especially in the regulation of the cardiovascular and respiratory systems, was clarified by F. V. Ovsiannikov, N. A. Mislavskii, and M. Flour-ens. The role of the cerebellum was elucidated by L. Luciani. The experimental study of cerebrocortical function was initiated soon thereafter by several German scientists, including H. Fritsh and E. Hitzig in 1870, F. Goltz in 1869 and H. Muck. However, the idea that the reflex principle might apply to cortical activity had already been conceived several years earlier by Sechenov in his Brain Reflexes (1863). A systematic experimental investigation of cortical function was begun by I. P. Pavlov, who discovered conditioned reflexes and, consequently, the possibility of objectively recording nervous activity in the cortex. A. A. Ukhtomskii introduced the principle of the dominant into neuropsychology.

Another line of research in neurophysiology focused on the mechanism of activity in neurons and on the nature of excitation and inhibition. This work was aided by the discovery and development of methods for recording bioelectric potentials. The recording of the electrical activity in nerve tissue and in the individual neurons permitted objective and precise determination of where a nerve impulse occurs, how it develops, and to where and at what rate it spreads along the nerve tissue. Among those who made valuable contributions to the study of the mechanisms of nervous activity were H. Helmholtz, E. Du Bois-Reymond, L. Hermann, E. Pfluger, and the Russian N. E. Vvedenskii, who used the telephone to study electrical responses in the nervous system in 1884. W. Einthoven and subsequently A. F. Samoilov accurately recorded brief, weak electrical responses in the nervous system by means of a string galvanometer. In 1924 the American scientists G. Bishop, J. Erlanger, and H. Gasser introduced electronic amplifiers and oscillographs into neurophysiological research. These technical advances were later combined in electromyography to investigate the activity of individual neuromuscular units. Another technical advance is electroencephalography, which records the total electrical activity of the cerebral cortex.

One of the main concerns of modern neurophysiology is the integrative activity of the nervous system. This is studied by transecting and removing different structures, by obtaining these structures’ electric potentials with surface and needle electrodes, and by stimulating the structures with electricity and heat. Other major achievements of neurophysiology include the discovery and detailed elucidation of the activating and inhibitory influences—both ascending and descending—of the brainstem reticular formation; the identification of the limbic system of the forebrain as one of the highest centers of integration for somatic and visceral functions; and the discovery of mechanisms within the hypothalamus for the higher integration of neural and endocrine regulatory systems.

Currently, detailed research using microelectrode techniques is being directed at the cellular mechanisms of nervous system activity. Using these techniques, it is even possible to detect electrical activity in a single neuron within the CNS. A neuron continues to functional normally for a while after intracellular microelectrode implantation. Microelectrodes have been used to discover how excitation and inhibition develop in different kinds of neurons, what the intracellular mechanisms of these processes are, and how an electrical impulse is transferred from one neuron to another. Equally important to the development of neurophysiology has been the introduction of electron microscopy, which has yielded detailed micrographs of the ultrastructure of neurons and interneuronal connections in the CNS.

These technical advances have enabled neurophysiologists to directly study the mechanisms by which information is coded and transmitted in the nervous system. The experimental use of chemical and physical agents for directly manipulating the activity of nerve cells has also been made possible by the introduction of microelectrode techniques, electron microscopy, and other technical advances. Models of individual neurons as well as of networks of nerves are being formulated on the basis of data obtained in direct experiments on the nervous system. Modern neurophysiology is closely allied with other disciplines, for example, cybernetics, neurochemistry, and bionics.

REFERENCES

Beritov, I. S. Obshchaia fiziologiia myshechnoi i nervnoi sistem, 2nd ed., vol. 1. Moscow-Leningrad, 1947.
Eccles, J. Fiziologiia nervnykh kletok. Moscow, 1959. (Translated from English.)
Eccles, J. Fiziologiia sinapsov. Moscow, 1966. (Translated from English.)
Prosser, C., and F. Brown. Sravnitel’naia fiziologiia zhivotnykh. Moscow, 1967. (Translated from English.)
Obshchaia i chastnaia fiziologiia nervnoi sistemy: Rukovodstvo po fiziologii. Leningrad, 1969. Sherrington, C. Integrativnaia deiatel’nost’ nervnoi sistemy. Leningrad, 1969. (Translated from English.)

P. G. KOSTIUK

References in periodicals archive ?
Three earlier studies of the force-velocity relationships of isolated muscle preparations and of in-vivo muscles under two different kinds of loading were reviewed to see what they may have revealed about the way contractile power-rates were limited intrinsically, or by the effect(s) of the various neural inhibitory structures and pathways identified by neurophysiologists. Overt differences between the respective force-velocity relationships were identified.
Thus, instead of focusing their energies on addressing the "where" question, or the question of where in the brain psychological activity takes place, Uttal implores neurophysiologists to instead ask a "what" question, that being, what are the necessary interactions between subregions of the nervous system for the emergence of perceptual and mental processes?
It is no accident that Sigmund Freud's rejection of the associational school of psychology that dominated European and American thought at the beginning of the century was considered "unscientific." The "scientific" evidence overwhelmingly supported the associational school of thought; human psychology is the consequence of associated elementary "functions." The more neurophysiologists explored the microstructure of the brain, the more the highly specialized functional architecture of the brain became obvious.
According to an editorial in the New England Journal of Medicine in April 1992, itching is an "orphan symptom, frustrating to patients and their physicians and sadly neglected by neurophysiologists and pharmacologists." The medical term for itching is not particularly appetizing: pruritus.
With the addition of SafePassage, NuVasive Clinical Services solidifies its leadership position as the largest provider of outsourced IONM services with more than 550 neurophysiologists and oversight physicians in the US, allowing for the delivery of services to over 1,000 customers and 3,000 surgeons.
Based on recent success in decoding non-invasive cortical recordings (EEG, MEG), and our multidisciplinary team (of engineers, neurophysiologists, psychophysicists, and audiologists), we propose to develop and implement algorithms to decode brain signals picked up by EEG electrodes to extract intention signals, and to match them to acoustic sources within the environment.
"The combination could benefit NuVasive's presence on the East Coast, where Impulse's 150 neurophysiologists are in hospitals where NuVasive has yet to make a dent," BMO Capital Markets analyst Joanne Wuensch said of the deal.
For neurophysiologists and electrical engineers, Varsavsky et al., who work in electrical and electronic engineering and neurology at the U.
Neurophysiologists Eric Trudel and Charles Bourque at the Research Institute of the McGill University Health Centre in Montreal, Canada, suggest the body's internal clock helps to regulate a water-storing hormone.
An essential reference for clinical neurophysiologists and neurologists, this book is also a useful resource for others involved in the field.
Among the more than thirty invited artists, all of whom evince an interest in phenomena that happen also to be of concern to neurophysiologists and cognitive psychologists, are Olafur Eliasson, Ellsworth Kelly, Bridget Riley, and Liz Lamer.
"Neurophysiologists now want to understand how muscles and nerves collaborate to produce springlike legs."