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But there were naysayers:

But there were naysayers:. Maybe with high frequency (300cps), square pulse (instant rise) ESB you are giving un-natural activation of CNS pathways. Maybe by activating entire central pathways, you are also doing something that doesn’t happen in nature. Sooooooo……. We did an expewriment:.

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But there were naysayers:

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  1. But there were naysayers: • Maybe with high frequency (300cps), square pulse (instant rise) ESB you are giving un-natural activation of CNS pathways. • Maybe by activating entire central pathways, you are also doing something that doesn’t happen in nature. Sooooooo……

  2. We did an expewriment: • Much slower soft starting stimulation at low frequency • & • We stimulated centrally the same density of fibers in and outside the descending inhibition.

  3. This was M & L’s very important theory of descending inhibition…(rather than suppression of higher pathways.

  4. Morphine had no effect on the aversive reaction threshold for the “Miss” at left (101% baseline). But it elevated the aversive reaction threshold of the “hit” to 320% baseline.

  5. Is there a summation of effects… • ….from 2 or more interacting sites? • First study was behavioral:

  6. But where were the summation(s)? • This required a study of single neuron responses to see if one lower level could be activated to a greater by two higher places than by either alone.

  7. Studying neurons in NRM presented us with a wrinkle: • Fields & colleagues at UCSF found that there were 2 kinds of cells in NRM, On Cells and Off Cells. • On cells turned on by pain, off by opiates. • Off cells ere the other way around: turned off by pain, on by opiates. • Thus cells had to be On/Off classified before studying summation effects. Classification done with tail flick in lightly anaesthetized rats, ala Fields.

  8. So, we showed that different brainstem sites interacted at RM… • But was one site (e.g., PAG) necessary for the other site (e.g., PGC) to function? This suggested a reversible lesion experiment:

  9. Naturally naysayers said “nay”… • “You are comparing a double injection (PGC-M + PAG-T) with a single one (PGC-M). “ • OK so we did the appropriate comparison to get the thing published:

  10. So of course next, we had to see what the lesions did to on and off cell responses.

  11. Moral of the story: • If you stay away from complex higher cognitive functions and study something simple (like sensory responsiveness, e.g., pain) then you can learn a lot with lesions & ESB

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