The Physiology of Controls on Sensory Pathways with Special Reference to Pain
The nature of the phenomenon of hypnosis has been described elsewhere in this symposium. In hypnotic anaesthesia, patients fail to report pain, fail to recall their experiences after surgery and fail to demonstrate those autonomic and withdrawal reflexes which are to be expected during injury to tissue. The present state of knowledge of the physiology of central nervous system mechanisms associated with pain is not sufficiently developed to offer any explanation at all for the bizarre and curious state of a hypnotized patient. This inability of physiologists is not surprising since no sensory process can be followed from stimulus to conscious experience. However, a considerable amount is known about pathways which conduct pain producing impulses from periphery to those higher structures traditionally associated with conscious experience. It is evident that in hypnosis an extraordinarily effective blockade can be established across these connections from afferent inputs to effector mechanisms. It is reasonable therefore to ask a physiologist to speculate on the possible sites of this blockade without his attempting to define the nature of the mechanisms which generate the orders which result in the setting up of the barricades.
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