ODOR SPECIFICITIES OF THE FROG^S OLFACTORY 



RECEPTORS* 



R. C. Gesteland, J. Y. Lettvin, W. H. Pitts and Aristides RojAsf 



Research Laboratory of Electronics, Massachusetts Institute of Technology, 

 Cambridge, Massachusetts 



A persistent obstacle to study of the vertebrate olfactory system has been 

 the experimental difficulty of finding out about the properties of the recep- 

 tor cells. Their relatively small cell bodies, sheathed distal processes, and 

 thin, unmyelinated axons have limited most of the experimental electro- 

 physiological investigations to recording a large number of units at a time. 

 Adrian's categories of some major types of odor response from the 

 olfactory bulb (Adrian 1953) and Ottoson's studies of differences in 

 slow potentials resulting from diff'erent stimuli (Ottoson, 1958) are the best 

 available data. Neither allows the properties of the receptors to be 

 described in enough detail to account for the sensitivity and selectivity of 

 the nose. Beidler and Tucker have described a method of recording from 

 a small bundle of axons of the olfactory nerve (Beidler and Tucker, 1955). 

 They have not yet published the results of their experiments. Zwaarde- 

 maker's early study of cross inhibition (Zwaardemaker, 1895) provided 

 as good a set of categories to describe psychophysical odor properties as 

 any, but it cannot lead to a unique description of the receptor mechanism. 

 Action potentials recorded from the second-order olfactory units located 

 in the bulb do not show unique responses to different stimuli; this may 

 mean that odor specificity information is coded as patterns resulting from 

 simultaneous activity of many second-order units. 



This paper describes a method of recording the action potentials of 

 olfactory receptors by using low-impedance extracellular metal micro- 

 electrodes (Gesteland, 1961). Some of the odor-specific properties of the 

 receptors will be described. 



*This work was supported in part by the U.S. Army Signal Corps, the Air Force Office of 

 Scientific Research, and the Office of Naval Research ; in part by the U.S. Air Force 

 (Aeronautical Systems Division Contract AF33(616)-7783) ; and in part by the National 

 Institutes of Health (Grant B-1865-(C3)). 



t Alfred P. Sloan Postdoctoral Fellow. 



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