Characteristics of radiation-induced performance changes in bar-press avoidance with and without a preshock warning cue.

Rats were trained to perform one of three tasks in which responses on a lever delayed the onset of footshock for 20 sec. One task provided a warning tone beginning 15 sec after the last response on the lever and lasting for 5 sec just prior to the presentation of a shock (fixed-interval signalled avoidance), while a second task provided no external cues (unsignalled avoidance). The third task was similar to the fixed-interval signalled avoidance task, except that the warning tone preceding shock began at varying intervals after the last response on the lever (variable-interval signalled avoidance). Animals trained on the signalled avoidance paradigms received fewer shocks than those on the unsignalled avoidance paradigm. After 10 krads of gamma radiation, animals performing on either task with cues were less able to avoid shock, although they recovered somewhat over a 90-min period. The animals not provided cues also experienced more shocks during the first 10 min after irradiation but were relatively less affected in performing the task. Response rates on the bar and the patterns of responding on these tasks were not significantly different after irradiation, except that animals responded after the onset of shock more often after irradiation than before. These results suggest that rats will continue to effectively use task related cues after irradiation, but that the relative degree of behavioral decrement may depend on the initial level of performance or possibly the complexity of the task.