The sense of smell promotes adaptive behaviors such as feeding and soothing, but how early humans begin to process odors represents a gap in knowledge for researchers.

In a study published in JNeurosci, Thorsten Kahnt from the National Institute on Drug Abuse and colleagues explored olfaction development in humans and revealed how early humans begin to smell. The researchers used fMRI to image the brains of sleeping infants as they inhaled appetitive (pleasant) and aversive (unpleasant) odors.

As early as one month of age, odors triggered activity in brain regions strongly associated with the sense of smell, as well as the thalamus, which is important for processing sensory information in general.

The strength of activation varied across odors, but unlike what is observed in adults, distinct odors did not trigger unique activation patterns. Additionally, nasal airflow findings from this study suggest that sleeping infants inhale more vigorously when scents are appetitive than aversive.