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preferred if this were something less than i per second. When such a 

 response was observed, a three-step experiment was performed : first, after 

 several minutes of waiting, a 30-second record was made on moving 

 photographic paper of the resting rate of the unit response. Second, an 

 elicitation test was made. A scries of twenty -j-second trains of stimulation 

 (sine wave 60 c.p.s., 50 namp.) was introduccci via the medial-forebrain- 

 bundle electrodes at a repetition rate of i every 2 seconds. These were not 

 correlated with single-unit response. Instead, there was an explicit effort 



Fig. 16 



Schematic diagram of single-unit operant-conditioning 

 apparatus. Single-unit response is amplified and fed into 

 amplitude discriminator which disregards all lesser signals, 

 but yields an output whenever the single-unit response 

 occurs; the output then goes to a counter. The counter is 

 preset to activate a stimulator and reset whenever it reaches 

 some number from i to 9. At this point, a |^-second train of 

 60-cycle stimulation (50 namp. r.m.s.) is delivered to the 

 medial-forebrain-bundlc 'reward' point. During the stimu- 

 lation, the counter is disengaged so that it will not count 

 stimulus artifact. Immediately afterwards, it commences 

 to count again until the preset ratio is again reached at 

 which point it delivers another 'reward' stimulus. 



made to stimulate only in the absence of single-unit responses. Immediately 

 after this test a second 30-second record of activity was made on film. In 

 the event of elicited effects, each stimulation produced a series of responses 

 from the unit, and no further tests were made. The microelectrode was 

 then advanced until a new unit response appeared. In the event that 

 elicited effects were not found, the experiment continued. Third, a 

 reinforcement test was made. The experimenter awaited a single-unit 

 response and, each time it appeared, immediately delivered a stimulus to 

 the hypothalamus. When this was done by hand, reinforcement could be 



