REVIEW OF RESEARCH IN U.S.S.R. 473 



tioned responses of the salivary glands and gut secretory organs following 

 radiation, a fact which would be anticipated from the known postexposure 

 histologic reactions of these organs. Thus any conditioned reflex study using 

 a secretory response is difficult to interpret. 



One would hope to eliminate such difficulties by using motor studies in 

 experimental animals. These are usually based on feeding reflexes, however, 

 and it is well known that irradiated animals show alterations in appetite 

 and spontaneous motor activity. They may develop an aversion to certain 

 foods for no known reason and may specifically avoid foods eaten shortly 

 before irradiation (Kimeldorf, 1961). Following anorexia, irradiated ani- 

 mals may develop an appetite which is stronger than normal, and this may 

 lead to important alterations in some psychologic testing situations. 



Conditional Reflex Studies 



The term "conditional" rather than "conditioned" is used in this report 

 because it represents a better translation of the corresponding Russian word ; 

 it has been advocated by a good many U.S. conditional reflex (CR) re- 

 searchers because it stresses the temporary or "noninnate" nature of CRs 

 (Brazier, 1959). 



Some assumptions concerning CRs which are generally taken for granted 

 by Soviet physiologists may be little known to Western radiobiologists. The 

 serious student of CR testing is urged to read Pavlov (1959) — there is now 

 available an excellent translation by Anrep — and the recent review of CR 

 studies by Grashchenkov (this volume) . At present Soviet physiologists often 

 use motor-feeding reflexes and include an instrumental response in their anal- 

 ysis. Thus, the typical modern CR test technique may be quite difTerent from 

 that using a dog in a harness and approximates a total-observation situation 

 of activity in an animal, as presented with a sequence of stimuli. In some 

 cases work has been done with dogs running free in a room, but more 

 commonly rodents in a small sound-proof chamber are used. Under these 

 conditions one can get information about the spontaneous motor activity of 

 the animal. However, CR studies do not lend themselves to tests of spon- 

 taneous preference, a technique which Western radiation researchers have 

 shown to be sensitive in postradiation experimentation. 



The magnitude of the response to the presented stimulus is of cardinal 

 importance. Pavlov demonstrated the important basic fact that a strong 

 stimulus produces a quantitatively larger response, as exemplified in measure- 

 ment of drops of saliva. The same holds true for motor reactions, as shown 

 in the force exerted by the animal. Typically, the animal is presented with 

 a fixed sequence of stimuli of varying strength (a "stereotype" of stimuli). 

 For example, one can use a sound of a certain frequency as the "strong" 



