J. OLDS AND M. E. OLDS 



167 



Of seventeen self-stimulators given this test, fifteen showed total failure 

 to regain criterion; the other tw^o were moderately impaired. Of six non- 

 self-stimulators given the test, three were moderately impaired, and three 

 were unaffected (Fig. 14). All animals were significantly impaired on the 

 initial learning test. This suggests that the points where impairment is 

 dissociated from self-stimulation are points involved in learning but not in 

 later memory or performance. 



M EMORY 

 PER I AMYGDALOID 



1/ .^ 



4 8 12 16 20 34 2B 32 3t 40 



H I PPOCAMPUS 



^--rr 



■! 20 30 



ANT. T HAL. 



/35//0 



.'-r 

 -)—^ 



Fig. 13 

 Memory test. Cumulative-error curves arc shown for days when stimulation started at 

 onset of test (double lines) and days when stimulation did not start until after criterion 

 was reached (single lines). Vertical dotted line indicates onset of stimulation for latter case. 

 When stimulation starts at onset of test, errors are not eliminated in any of these cases. 

 When stimulation is introduced after criterion, it causes complete relapse with electrodes 

 in periamygdaloid cortex, but not complete relapse with hippocampal or anterior thala- 

 mic electrodes. 



Now the question arises whether, in places where self-stimulation and 

 confusion are associated, the confusion results from the extreme reward 

 (which might render the food reward unimportant), or from some 

 additional pattern disruption over and above this reinforcing effect. 



(5) Reuiforcement-Jutcrfcreuce Test. — To attempt an answer to this 

 question, a test was devised in which the 'interfering' stimulus was so 

 correlated with the correct response as to constitute to some degree an 



