The first smell you associate with an object is given privileged status in the brain.
Yaara Yeshurun and colleagues at the Weizmann Institute of Science in Rehovot, Israel conducted a study on smells and memory, using functional magnetic resonance imaging. The hippocampus showed a characteristic pattern of neural activity when particular smells were represented to the participants. The researchers concluded that the brain reserves a special pattern of activity for memories that represent the first time we have associated a smell with a particular thing – and that such pairings are most likely to be laid down in childhood.
The brain may have evolved to lay down these privileged memories because it enhanced our ability to sense danger. "This is especially true for unpleasant odours," says Yeshurun.
This makes sense, says Rachel Herz, author of The Scent of Desire: Discovering our enigmatic sense of smell and visiting professor at Brown University in Providence, Rhode Island. "The evolutionary implication is that the situation in which you first encounter an odour is likely a reliable maker for its meaning, and it is highly adaptive to learn that meaning so that the odour can be responded to appropriately in the future."
This study provides more information about the importance of ensuring immediate skin to skin experience for newborn babies and their mothers. When mothers and babies are enabled to maintain skin to skin proximity at birth, both mother and baby are mapped neurologically to each other through their olfactory system. The importance of this neurological olfactory mapping between mother and baby is profound in terms of the baby identifying feeling safe, secure and calm in her/his mother's presence and having those feelings triggered by the scent of the mother. The feelings the mother experiences with the scent of her baby from birth patterning can be recognised to be similarly profound for the vibrancy of the relationship between them.
ScienceDirect - Current Biology : The Privileged Brain Representation of First Olfactory Associations