NEUROPHYSIOLOGY: STATUS, TRENDS AND NEEDS 



By Philip Bard 

 School of Medicine, The Johns Hopkins University 



It is not easy to define neurophysiology 

 in terms that sharply distinguish it from 

 other branches of neurobiology. Perhaps 

 one may begin with Sherrington's state- 

 ment that the nerve impulse is "the uni- 

 versal currency of the nervous system." 

 Apart from mediating in some undeter- 

 mined manner the trophic influence exerted 

 by the nerve cell body on all parts of the 

 neuron, the only known function of ma- 

 ture neurons is to conduct impulses which 

 have specific effects on effector organs or 

 on other neurons. Neurophysiology is pri- 

 marily concerned with nerve impulses 

 whether they course in peripheral nerves 

 or through the complex channels of the 

 central nervous system. The neurophysiolo- 

 gist of today has the same regard for his 

 knowledge of nerve conduction that the 

 immediate followers of William Harvey 

 had for the demonstration that the blood 

 circulates because of the motions of the 

 heart. It is with this basic knowledge that 

 he proceeds to analyze further the prop- 

 erties of the individual neuron or to con- 

 sider the ways in which countless neurons 

 within the central nervous system deter- 

 mine the behavior of the organism. Thus 

 one may very simply depict but not ade- 

 quately define the subject. 



At the present time active interest in the 

 experimental exploration of the functional 

 aspects of the nervous system seems to be 

 satisfactory in the sense that during the last 

 twenty-five years this field of research has 

 recruited its fair share of investigators. Al- 

 though many of these were trained primar- 

 ily in physiology it is significant that some 

 of the most outstanding contributions to 

 neurophvsiology have been made by work- 

 ers who are the products of other discip- 

 lines. Conspicuous among these are in- 

 dividuals who began their scientific careers 

 in physics, in psychology, or in either de- 



scriptive or experimental morphology. 

 There are also many contributors to the 

 subject who appropriately continue to be 

 classed as zoologists, anatomists, biophy- 

 sicists, psychologists or neurosurgeons. This 

 heterogeneity of the sources of neurophysio- 

 logical information emphasizes the funda- 

 mental unity of the several subdivisions of 

 neurobiology. It has doubtless produced 

 a certain degree of hybrid vigor, a point 

 that should be taken into consideration in 

 any selection of the progenitors of the 

 neurophysiology of the future. 



PRESENT TRENDS AND NEEDS 



1. The Mechanism of Conduction of the 

 Nerve Impidse. This fundamental branch 

 of neurophysiology developed rapidly in 

 the 1920s and attained a high plateau of 

 achievement in the work of Erlanger and 

 Gasser. Interest has continued and there 

 is little basis to fear that it will be neg- 

 lected. The recent and current activities 

 of Hodgkin, of Curtis and Cole, of Lorente 

 de No and many others suggest that the 

 remaining mysteries of the local excitatory 

 state as well as those of the mechanism 

 of propagation of excitation along the 

 neuron may be substantially reduced in the 

 near future. In this sphere perhaps the 

 least understood aspect is the way in which 

 energy is made available for conduction, 

 particularly for the restitution of the rest- 

 ing potential. It appears that the tech- 

 niques of the enzyme chemists are not yet 

 adequate to determine with assurance the 

 specific chemical changes, but recent ex- 

 perimental results which relate the resting 

 and action potentials to chemical sources 

 of energy and transport of ions provide 

 assurance that very significant advances 

 are being made. 



2. The Physiology of the Synapse. This 

 topic includes the problem of the transmis- 



