A Sensitive Homecage-Based Novel Object Recognition Task for Rodents.

Area of Science:

• Neuroscience
• Animal Behavior
• Cognitive Science

Background:

• Traditional novel object recognition (NOR) tests in rodents have limitations including low sensitivity, potential odor confounds, and stress from out-of-cage testing.
• Developing a sensitive, reliable, and less stressful NOR paradigm is crucial for advancing rodent cognitive research.

Purpose of the Study:

• To introduce a novel, homecage-based NOR paradigm designed to enhance sensitivity and minimize confounds.
• To validate the utility of this new paradigm in both rats and mice across different sexes.

Main Methods:

• A three-step homecage paradigm using four stimuli per trial: familiar objects (FO), novel object 1 (NO1) soiled with cage bedding, and novel object 2 (NO2) similarly soiled.
• Animals (rats and mice, both sexes) first sampled FO, then were tested with NO1, followed by a test with NO2.
• Stimuli were inexpensive wooden beads, with unique sets for each animal to eliminate odor confounds.

Main Results:

• Both male and female rats and mice explored NO1 significantly more than FO in Step 2, indicating successful novelty detection.
• Rats showed a clear preference for NO2 in Step 3, demonstrating robust novelty recognition.
• Female mice showed a preference for NO2 in Step 3, but male mice did not, suggesting Step 3 parameters may be challenging for mice.

Conclusions:

• The developed homecage NOR paradigm is sensitive, reduces stress, and eliminates odor confounds, making it suitable for rats and mice.
• The paradigm's flexibility allows for adjustments in sampling phase duration and inter-trial delay to tailor task difficulty.
• This method offers a valuable tool for quantifying novel object recognition across sexes and species in a controlled, homecage environment.