Effects of predictable and unpredictable intermittent noise on spatial learning in rats.

The effects of predictable (periodic) and unpredictable (aperiodic) intermittent noise of moderate intensity (68 dB) on the learning of a complex T-maze by genetically defined rats were investigated. In Experiment 1, three groups (n=8) of rats learned a multiple T-maze, one group under control conditions, one group with predictable intermittent noise and one group with unpredictable intermittent noise. Results showed a profound effect of noise on learning and behavioural scores. Noise-exposed animals made less errors, finished their trials sooner and explored less. There was no difference between predictable and unpredictable noise. Further tests, during which formerly noise-exposed groups learned a new route under control conditions (Experiment 2) or the former controls learned a new route with noise (Experiment 3), suggest that the effects of noise on learning were caused by an effect of noise on memory formation and/or retrieval, rather than by long-term shifts in behavioural strategies.