Rabin, B. M., Joseph, J. A. and Shukitt-Hale, B. A Longitudinal Study of Operant Responding in Rats Irradiated when 2 Months Old. Radiat. Res. 164, 552–555 (2005).

Two-month-old rats were exposed to ⁵⁶Fe particles (1, 1. 5, 2 Gy; 1 GeV/nucleon). They were tested on the performance of an ascending fixed-ratio operant task (bar pressing for food reward) at 7, 11 and 15 months after irradiation. Previous research had shown that for the same rats tested at 3 months after exposure, only the rats exposed to 2 Gy of ⁵⁶Fe particles showed a significant disruption of performance compared to control (0 Gy) rats. When these rats were tested 7, 11 and 15 months after exposure, all irradiated groups showed significantly poorer performance than the controls. These results suggest that there is an interaction between irradiation and age such that ⁵⁶Fe-particle-induced performance deficits can develop several months after exposure.