Odour learning and immunity costs in mice.

Area of Science:

• Behavioral neuroscience
• Immunology
• Animal behavior

Background:

• Learning is energetically demanding.
• Potential trade-offs exist between cognitive effort and immune function.
• Previous studies suggest a link between learning and susceptibility to infection.

Purpose of the Study:

• To investigate the metabolic costs of learning.
• To examine the relationship between odor learning complexity and immune function in mice.
• To determine if increased learning effort impacts susceptibility to infection.

Main Methods:

• Outbred male laboratory mice (BKW strain) were exposed to varying numbers of urinary odors for learning tasks.
• Odor habituation and preference for novel over familiar odors were assessed.
• Mice were subsequently infected with Babesia microti to measure infection susceptibility.
• Corticosterone levels and peripheral antibody titers (total IgG) were analyzed.

Main Results:

• While odor learning affected habituation, retention of learned odor profiles was consistent across different learning complexities.
• Infection rates with Babesia microti increased significantly with the number of odors mice had to learn.
• Failure to learn in more complex tasks, rather than maintaining learning performance, was associated with greater infection.
• No direct relationship was found between infection and peripheral antibody (total IgG) titer.

Conclusions:

• Increased odor learning effort incurs metabolic costs, leading to a trade-off with immune function and increased infection susceptibility.
• The data suggest that difficulties in learning, not the maintenance of learning, drive this trade-off.
• These findings align with broader evidence linking cognitive load, stress hormones (corticosterone), and immune system function.