5i6 



BRAIN MECHANISMS AND LEARNING 



outside the animal's reach for 2 seconds. The stimukis box was then pushed 

 forward, and the animal was allowed to respond. Thirty trials (fifteen 

 positive and fifteen negative trials) were executed each day until the 

 animal reached a criterion of 90 per cent correct in a one-day session. The 

 EEG was recorded for every trial with a Grass 4-channcl model III 

 machine. 



The six monkeys learneci a total of fourteen visual discriminations. The 

 plot of percentage of correct responses in successive daily sessions showed 



Fig. 4 

 Photograph to show the testing situation. A, monkey in chair, with the black screen 

 around the chair removed to show the electrode wires; B, opaque screen moved to one 

 side to expose the stimulus box; C, the flickering light passing through the box to 

 illuminate the visual stimulus attached to the box frontal panel; D, the photic stnnulator; 

 all controls are operated manually. 



the typical postively accelerated learning curves. The number of trials 

 ranged from 90 to 180. EEG recordings of eleven discriminations were 

 suitable for analysis. 



The normal EEG of the visual area showed the fast, low voltage arousal 

 pattern mixed with 4-5 per second relaxation waves. Occasionally there 

 were some alpha-like waves. The temporal leads showed periodical 

 (every 2-3 seconds) bursts of waves (100 (jv. and 12-16 per second) super- 

 imposed on the arousal and relaxation record. These bursts were very 



