Handling, task complexity, time-of-day, and sleep deprivation as dynamic modulators of recognition memory in mice

Sleep is essential for optimal cognitive functioning. Although we lack a complete understanding of the role of sleep in memory consolidation, we know that various factors that disturb sleep or sleep quality have consequences for cognitive performance. Such factors can be unintended components of behavioral experiments on rodents and other experimental animals that generate differing results from different labs. These experimental variables include habituation to handling, intended or unintended sleep deprivation, task complexity, time of testing, and environmental features. We have examined how these variables impact recognition memory in C57BL/6 mice. Handled mice outperformed their non-handled counterparts across different combinations of delay phase duration and lighting conditions. Results also suggest that simple task recall is more resistant to diurnal variation and the impairing effects of sleep deprivation than is complex task recall. This study underscores the role of protocol and environmental factors in recognition memory and in conflicting results from different laboratories.