R. W. DOTY AND C. GIURGEA 



14-1 



52 to 84. The first CR was seen on the sixty-seventh pairing. The right 

 arm was flexed to the level of the restraining collar, then extended along 

 its lower surface with hngcrs fluttering as though seeking an object. In 

 the next forty-seven trials a movement similar to this occurred to the CS 

 thirty-one times. At the threshold current of 0.55 mA. or during the later 

 phases of subsequent extinction sessions the movement was more likely to 

 be a simple flexion very similar to that evoked by the US (Fig. 4). Even 

 when the movement was vigorous, it often terminated prior to the US. 



3 .? 





^^*SK 



Fig. 4 

 Responses o( Monkey 1, enlarged from a 16 mm. colour film which was taken through a 

 one-way mirror. Left and centre: conditioned flexions of right forearm to CS at left occipital 

 cortex. The slight inclination of the head to the right, which also imitates a movement of the 

 UR, was sometimes seen with high intensities of the CS before conditioning was begun and 

 hence cannot accurately be considered a part of the CR, although its consistency and tiireshold 

 of elicitation may have been altered by the conditioning procedure. The CS and US signal 

 lights were used only during photography. Ri^ilit: unconditioned response to stimulation of 

 left precentral cortex. Note similarity of end point of this response to that obtained by Dclgado 

 from stimulation of the rhinal fissure (Delgado, 1959, Fig. i top). 



In ninety-one presentations of the CS given in five sessions without the 

 US this CR was elicited fifty-six times. One-minute intervals were 

 frequently employed. In two sessions after repeated presentations of the 

 CS without the US, the CR was absent for five or more consecutive 

 trials. The head and eye movements evoked by the CS were still present 

 during this period of extinction. On several occasions it was noted, how- 

 ever, that the eyes closed at the onset of the CS and the animal appeared to 

 drowse even though the eyes could be seen moving beneath the lids. 



Stimulation with an electrode pair within 1-} mm. of those used as CS 

 gave no eye movements if the polarity of the stimulus was negative for the 

 electrode separated from the others by a small sulcus. None the less the 



