Effects of Ionizing Radiation on Auditory and Visual Thresholds
Technical rept. 9 Oct 1987-28 May 1991
JOHNS HOPKINS UNIV BALTIMORE MD SCHOOL OF MEDICINE
Pagination or Media Count:
An experimental analysis of the effects of low-dose ionizing radiation on sensory and motor function was conducted in baboons. Animals were trained using a reaction time procedure to respond to near-threshold acoustic and visual stimuli, and quantitative assessments were made of radiation-induced changes in absolute auditory and visual thresholds and reaction times. Animals received multiple exposures at single fractionated dose levels of 1, 2, and 5 Gy. Single exposures at higher exposure levels of 10 and 15 Gy were also examined. 100-200 cGy exposures produced transient changes in reaction times. Transient Increases in reaction times occurred following low-dose exposures, usually within 1-3 weeks following the exposure. These increases typically recovered to normal baseline levels within 2-3 weeks. 1000 and 1500 cGy exposures produced long-term hearing deficits which were not frequency-specific. The severe hearing loss was most likely due to a sensorineural deficit, since complete loss of function of the tympanic membrane or middle ear ossicles would be expected to produce a hearing loss about 50-55 dB. These higher radiation doses have had less of an effect on visual intensity thresholds, producing a 5- lO dB deficit in visual thresholds. No physical damage to the cornea iris lens or retina was observed. Behavioral Analysis, Sensory-motor Functions, Reaction Time, Auditory-visual Thresholds.
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