We examined the effects of noise on acquisition and retention of the spatial memory task in equal and unequal context in adult male rats. The natural noise in Azadi football stadium was recorded and measured by sound level meter instrument and set in high (HI), moderate (MI), and low (LI) intensities, 86, 64, and 47 decibels A (dbA), respectively. Rats were trained in Morris water maze (MWM) for 3-consecutive-day program and at day 4 visible and probe tests were done under one of the above noise intensities. The retention was evaluated at day 7 on the basis of equal and unequal noise exposure situation. Escape latency, traveled distance, and swimming speed were recorded and used for subsequent analysis. Our results showed significant increases in the escape latency and traveled distance by increasing the noise intensity during acquisition period, and also retention test in equal noise situation. Furthermore, retention test in the group that was under HI noise during both training period and retention test escape latency and traveled distance compared to the groups which was under HI noise during training period and LI or MI noise during retention test (HI-LI or HI-MI).

A wide range of animal and human investigations have tested the neurobiological and immunological aspects of noise. Few studies, however, have explored the behavioral characteristics of noise on neuromotor movements. To examine this correlation, we tested the effects of continuous intensive noise on retention and contextual transfer in a spatial memory task in adult male rats. The natural noise was recorded in a football stadium and set at high (HI), moderate (MI), and low (LI) intensities, levels corresponding to 86-90, 64-68, and 52-54 A-weighted decibels (dbA), respectively. Rats were trained in a Morris water maze for 3 consecutive days. On day 4, visible and probe tests were conducted under the same intensities. Retention was evaluated on day 7 with high-intensity noise exposure. The contextual transfer test was held on day 8 after exposure to 30-min highintensity noise. The escape latency and distance traveled were recorded and used for subsequent analyses. Our results showed significant increases in latency and distance traveled, attributable to increasing the noise intensity during the acquisition period. Additionally, performance in the LI group was significantly impaired in the retention test at the high intensity. In the contextual transfer test, results showed no significant increase except in the LI group, whereas a higher latency and distance traveled were found in the HI group. High-intensity noise appeared to damage the learning process. However, because the most robust results were found in the MI group, training with moderate-intensity noise can promote better performance under continuous highintensity noise.