Bright lighting conditions during testing increase thigmotaxis and impair water maze performance in BALB/c mice.

In this study, we investigated the performance of BALB/c mice in Morris water maze task under two different illumination (bright and dim light) conditions. The results show that BALB/c mice could not complete the Morris water maze task under bright light (BLC), but performed very well under dim light (DLC). Animals that swam under BLC had a higher serum corticosterone level than those under DLC. Animals pretrained under DLC had a lower serum corticosterone level than those directly exposed to BLC. Our results also show that animals under BLC had a higher level of thigmotaxis (a behavioral anxiety measure during testing) than under DLC. Correlation analysis shows that corticosterone and thigmotaxis levels have a positive correlation with escape latency, indicating that corticosterone and thigmotaxis levels have a negative correlation with learning/memory performance. These results suggest that BALB/c mice have the ability to learn a spatial task; under BLC, they performed poorly owing to a high level of thigmotaxis.