IjS BRAIN MECHANISMS AND LEARNING 



appeared to follow much more ordinary acquisition and extinction 

 patterns, augmenting at each reinforcement, slowing upon cessation of 

 the reinforcement procedure, often coming to rest at a higher firing rate 

 than the original rate, but lower than during reinforcement. 



Changes of this type were graded along a dimension of rapid or slow 

 conditioning. With units in the anterior rhincnccphalic cortex, condi- 



I Betoo S 



!092 ■ Hipptxompyi Proper 



miiimmimmm'imim'itmt m i nm » ■ n i ii i ii " 



in Mm Rl< 



fm0' 



V [X...r.g Si No Rft 



Fig. 19 

 Expennieut on single-unit response recorded from hippocampus. It is noteworthy that stimula- 

 tion which closely follows a unit discharge (see IV) causes a burst of activity which is not seen 

 when stimulus occurs against a background of no-firing (see V). 



tioning was quite as fast as with type I units in the dentate gyrus. But the 

 response was more moderate. Some 'learning' of a much slower order 

 occurred with points estimated to be at the base of the neocortex. There 

 was never any possibility of augmenting the rate by manual reinforcement 

 with electrodes, here, but, left on automatic reinforcement for long 

 periods of time, the unit response rate would sometimes increase 

 gradually. This seemed quite like the conditioning of a skilled act in its 



