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Updated: Aug 12, 2026
A Lateralized Odor Learning Model in Neonatal Rats for Dissecting Neural Circuitry Underpinning Memory Formation
Published on: August 18, 2014
Unilateral olfactory conditioning in 6-day-old rat pups
Insights
Early olfactory learning in rats shows brain lateralization. This suggests developing rodents may form scent memories in brain areas accessed by only one nostril during learning.
Area of Science:
- Neuroscience
- Developmental Psychology
- Olfactory System Research
Background:
- The maturation of brain commissural systems, crucial for bilateral communication, occurs after the first week of postnatal life.
- Early olfactory learning in rodents is hypothesized to be laterally organized due to incomplete neural pathway development.
Purpose of the Study:
- To investigate the potential lateral organization of early olfactory learning in 6-day-old rats.
- To determine if olfactory memories are formed in brain structures accessible by a single nostril.
Main Methods:
- Rats were trained using odor-milk pairings with one nostril occluded.
- Testing involved assessing conditioned responses with either the trained or untrained nostril open.
- Behavioral activation and oral responses were measured as conditioned outcomes.
Main Results:
- Conditioned orientation to an odor was observed only when the trained nostril was open during testing.
- Rats demonstrated odor preferences consistent with the nostril open during specific odor training.
- Lateralization was observed for conditioned oral responses but not for behavioral activation.
Conclusions:
- Olfactory memories in developing rodents may be represented in brain structures allowing unilateral access during learning and testing.
- These findings suggest a basis for isolating the neural substrates of olfactory conditioning in early development.
Abstract:
The potential that early olfactory learning might be laterally organized in the brain was investigated in 6-day-old rats. This hypothesis is based on the finding that the commissural systems that subserve bilateral olfactory communication do not mature until the second week of postnatal life. Pups were trained with pairings of cedar odor and intraoral infusions of milk while one nostril was occluded. Animals expressed a conditioned orientation towards cedar if tested with the trained nostril open. No such conditioning was observed if the untrained nostril was open during testing. Further, when individual pups received cedar odor/milk pairings with one nostril open and orange odor/milk pairings with the other open, they expressed a conditioned preference for orange when tested with the orange-trained nostril open, and a preference for cedar when tested with the cedar-trained nostril open. Classically conditioned oral responses (mouthing) also appeared to be lateralized. However, no such unilateral conditioning occurred with respect to behavioral activation, which is also conditioned in this paradigm. Increases in activity to the odor CS were observed regardless of whether the trained or untrained nostril was open during testing. These results suggest that in developing rodents, olfactory memories may be partly represented in structures that can be unilaterally accessed during training and testing. They provide a starting point for isolation of neural substrates of the olfactory conditioning process.
