276 



BRAIN MECHANISMS AND LEARNING 



more clear-cut after T (Fig. 6 — left column — first line; 8 — I-II-III; 

 9 — I; II — I-II); P2 variations appeared to be a consequence of modifica- 

 tions in Ni and N2 (Figs. 6 — left column — hrst and fourth lines; 8 — III, 



EFFECT OF T ON POT EV. BY SS ON CSC 

 I SINGLE 3-1/ // PAIRS 10 msec 3-v 



s/7. 



/// PAIRS 100 msec 3 



IV PAIRS 100 msec 2.5 -^ 





Fig. 8 

 effect of tone upon potentials evoked by subcutaneous stimuli. advan- 

 TAGES OF PAIRED SHOCKS. I, Single shocks at 3 c.p.s. : slow, labile phenomena 

 are obvious and respond to T. II, pairs (10 msec, interval) at 3 c.p.s.; Ill, pairs 

 (100 msec.) at 3 c.p.s.; IV, pairs (100 msec.) at 2.5 c.p.s.; application of second 

 shock facilitated development of late, slow waves affected preferentially by 

 T application; contrastingly, responses to first shocks are either small or 

 suffered little modification. 



IV; II — I). When present in control responses, N3 was markedly 



reduced or abolished by T (Figs. 6 — left column; 8; 13— I; 10 — I; 11). 



Paired shocks (at i-ioo msec, intervals) or different stimulation 



frequencies (2.5-8 c.p.s.) were used to enhance slow phenomena and thus 



