E. GARCIA-AUSTT, J- BOGACZ AND A. VANZULLI 



617 



constant tone was emitted at the end of the period ot darkness, tor example 

 durmg the last 10 seconds, the response became dishabituated after three 

 to eight trials (Fig. 8). The nicrease in amplitude was marked and in some 

 cases surpassed the initial amplitude prevailing before habituation. This 

 phenomenon was always more marked and more rapid than the dis- 



^ "W^ 





Fig. 8 



Clhviges ofllie I'imal evoked response by effect of tone-flicker ctssociotion. 

 Stroboscope at 3 m. from the retina. Eyes open. Forty superimposed 

 sweeps. Lead C4-right mastoid 10/20 system. Arrows indicate the 

 stimulus. Discontinuous flicker frequency 2/sec. during 20 seconds, 

 interrupted during 20 seconds, (i) control without stimulation; (2) 

 habituation to discontinuous flicker frequency after twelve trials 

 without association with tone. A response of low amplitude and 

 after discharge of i6/sec. is observed. Three to eight successive trials 

 with tone (10 seconds) — flicker (20 seconds) — darkness (10 seconds) 

 association; (3) ist trial with tone-flicker association, no appreciable 

 changes were noted in respect to previous one; (4) 3rd trial, slight 

 increase in amplitude of response; (5-8) 4th, 7th, 9th, nth trials 

 respectively, the response continues increasing and is simplified. 

 Calibration, 100 msec. 



liabituation provoked by the discontinuous tiicker stimulation without 

 association of sound. 



If the trials with this tone-flicker association were prolonged rehabitua- 

 tion of the response was obtained. This rehabituation was more delayed 

 and inconstant than that in the darkness-flicker association, requiring 

 fifteen to twenty trials to appear. 



