E. GARCIA-AUSTT, 



BOGACZ AND A. VANZULLI 



6ll 



preferably in the occipital region. In other regions they were recorded 

 inconstantly. 



The lesser variability of the occipital response was more clearly shown 



I 



Fig. 3 



Clmiiges of the visual evoked response by effect of habituation and attention. Continuous flicker 

 frequency 2/sec. Stroboscope at 1.5 m. from the retina. Eyes open. Forty superimposed 

 sweeps. O2 and C4, controls, leads of the 10/20 system, common reference in the right mastoid, 

 (i) flashes 1-40, same leads, complex responses are observed on O2 and C4; (2) flashes 1081- 

 1120, habituation of the response on C4; on O2, no modifications are observed; (3) flashes 

 1121-1160, the subject counts number of flashes, the response increases on C4, on O2 no 

 changes (dishabituation by attention) ; (4) flashes 1 161-2000, without counting flashes, response 

 is again reduced on C4 as in (2), on O2 no changes. Calibrations, 100 msec, 100 microvolts. 



when the intensity of the flash was increased by bringing the stroboscope 

 near the retina. In some cases with the stroboscope placed at a distance of 

 1.50 m. or less from the retina, no changes were observed in the amplitude 

 of the occipital potential even when the flicker stimulation was prolonged 



RR 



