[Nonspecific activation response upon exposure to unanticipated and voluntarily controlled acoustic stimuli]

Normal subjects revealed these components of startle-response to unexpected stimulation followed by no visible wincing: blink reflex, facilitation of spinal motoneurons (augmentation of the H-reflex), the EEG vertex potential, and skin galvanic response. With voluntary, control of the stimulation the components of the response are either absent or less obvious, excepting skin galvanic response. The weakening of the startle-response in this case seems to be associated with the mechanisms of the selective sensory attention and to be determined by cortico-fugal inhibition of reticular interneurons mediating in this response.