JERZY KONORSKI 121 



activated not only during the operation of the stimuhis but also, by virtue 

 of reverberating circuits connected with them, some period after their 

 cessation (group 2) ; neurones which are activated only after the cessation 

 of the stimulus (pure oft-elements (group 3)). This is illustrated in Fig. 2. 



Fig. 2 



Diagrammatic representation of the physiological structure of a trace stimulus. 



The X axis represents time, t,, is the beginning of the operation of the particular stimulus, 

 tj, its termination. 



Along the y axis arc represented three groups of neurones: (i) a group of neurones activated 

 during, and only during the operation of the stinuilus; (2) a group of neurones activated both 

 during the operation of the stimulus and, owing to the reverberating circuits of neurones, for 

 some time after its termination; (3) a group of neurones activated niter the cessation of the 

 stimulus (off-neurones). All off-neurones are represented as acting for some time after the 

 cessation of the stimulus by way of reverberating circuits. On the left the respective type of 

 neurones of each group is indicated. The horizontal lines represent the periods of excitation of 

 each particular neurone. The whole group I is activated only during the operation of the 

 stimulus, some quickly adapting on-elemcnts being also shown. Group 2 is activated during 

 the operation of the stimulus and after its cessation, gradually becoming less active in the 

 course of time. The v.'hole group 3 is activated by the cessation of stimulus and then becomes 

 gradually less active as in the case of group 2. Further explanations in text. (After Konorski 

 and Lawicka, 1959. Acta Biologiae Experitnentalis, 19, 175-198.) 



As we sec the neurones of group i, being activated only during the 

 operation of the stimulus, but not after its cessation, are responsible only 

 for its actual ei^ccts; group la — i.e. the pure on-neurones group — 

 causes the beginning of the stimulus to have a greater reflexogenic 

 strength than its continuation — a well-known fact from CR experiments. 

 On the other hand neurones of group 2 continue to be activated after the 

 cessation of the stimulus and thus form a basis of the recent memory traces 

 of that stimulus. As far as neurones of group 3 are concerned — pure off- 

 elements — they account for the active role played by the cessation of a 



