Dissociation of sensation and evoked responses by a general anesthetic in man.

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Abstract
7 healthy volunteer Ss gave extracranial evoked responses and peripheral neurograms to suprathreshold electrical stimulation of ulnar nerve. Absolute psychophysical thresholds also were obtained. Ss then breathed cyclopropane at subanesthetic concentrations up to 4.3%. Evoked responses greatly diminished and in 3 Ss finally vanished as concentration increased. Absolute thresholds rose somewhat but never approached the intensities used to test evoked responses. All Ss could still detect stimuli and discriminate different intensities. Peripheral neurograms were unaffected. Inhalation of room air reversed the changes in evoked responses and in thresholds. Extracranial evoked activity thus seems unnecessary for at least some sensory experiences. (15 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)