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United States Department of Agriculture

Agricultural Research Service

Research Project: NEUROCOGNITION/NEUROSCIENCE Title: Interaction between age of irradiation and age of testing in the disruption of operant performance using a ground-based model for exposure to cosmic rays

Authors
item Rabin, Bernard -
item Joseph, James
item Shukitt-Hale, Barbara
item Carrihill-Knoll, Kirsty -

Submitted to: American Aging Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 15, 2011
Publication Date: February 1, 2012
Citation: Rabin, B.M., Joseph, J.A., Shukitt Hale, B., Carrihill-Knoll, K. 2012. Interaction between age of irradiation and age of testing in the disruption of operant performance using a ground-based model for exposure to cosmic rays. American Aging Association. 34:121-131.

Interpretive Summary: Exposure to high-energy radiation causes a decline in cognitive ability. While previous research has shown a decrease in cognitive ability in radiated rats based on age, the present experiment was designed to observe the effects of radiation age (i.e., age at the time of radiation) independently of testing age (i.e., age at the time of behavioral testing). Male rats ranging from 2-16 months of age were exposed to different doses of iron particles. Following irradiation, the rats were trained to make a particular response (lever press) on a schedule where more presses were required to get a food pellet. Testing began 2-4 months after irradiation and continued at 4-5 month intervals as long as there were sufficient numbers of rats for statistical analysis. The results seem to indicate that performance deficits are not necessarily a function of age, but instead are dependent on an interaction between the age of irradiation, the age of testing and exposure to radiation. The nature of these effects and how the age of irradiation affects cognition after 15-16 months remains to be established.

Technical Abstract: Exposure to HZE particles produces deficits in cognitive performance. While previous research has shown a progressive deterioration in cognitive performance in radiated rats as a function of age, the present experiment was designed to evaluate the effects of age of irradiation independently of the age of testing. Male Fischer-344 rats, 2, 7, 12 and 16 months of age, were exposed to 25-200 cGy of 56Fe particles (1000 MeV/n). Following irradiation the rats were trained to make an operant response (lever press) on an ascending fixed-ratio schedule. Initial testing commenced 2-4 months following irradiation and continued at 4-5 month intervals as long as there were sufficient numbers of subjects for statistical analyses. When performance was evaluated as a function of both age of irradiation and testing, the results showed a significant effect of age on the dose needed to produce a performance decrement. When performance was evaluated as a function of age of irradiation (with age of testing held constant), the results indicated that age of irradiation was still a significant factor influencing the effects of exposure on operant responding at both test ages (11-14 and 17-18 months). Dose was also a significant factor influencing operant responding in the rats tested at 11-14 months of age, but not at 17-18 months of age. The results are interpreted as indicating that the performance decrement is not a function of age per se, but instead is dependent upon an interaction between the age of irradiation, the age of testing and exposure to HZE particles. The nature of these effects and how age of irradiation affects cognitive performance after an interval of 15-16 months remains to be established.

Last Modified: 10/20/2014