5l8 BRAIN MECHANISMS AND LEARNING 



shows the EEG records of four negative trials taken from the second day 

 of training of monkey Ci. The EEG tracings show the four possible 

 combinations of alterations (visual area: photic driving or not driving; 

 temporal area: decreased amplitude or not decreased amplitude) in four 

 trials. Fig. 6 was taken from another monkey, who responded correctly to 

 the negative trials. Again, the four combinations appeared in the four 



4 



M 2 

 TC 96% 



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5 



LV 

 . LT 



L V LV t. 



Fig. 6 

 EEG records of four negative trials taken from the fourth day of training. Monkey M2 

 reached criterion on triangle and circle discrimination on that day, and made correct responses 

 (not reaching the stimulus) to these four trials. Trials 4 and 5 show the decreased amplitude of 

 temporal EEG, and trials 5 and 2 show photic driving in the visual area tracings. The break in 

 the upper tracing of light flashes indicates the presentation of the stimulus. LT, left temporal; 

 LV, left visual; calibration, 50 lav. and i second. 



trials. Similar examples could also be chosen from positive trials. Thus, it 

 may be misleading to use sample records demonstrating EEG changes 

 during learning. Some quantitative measurements are necessary to estab- 

 lish consistent trends. Fig. 7 presents such an analysis of two monkeys' 

 EEG records on two visual discriminations. Tracings from the temporal 

 and visual areas were plotted separately, with postive trials (vertical 



