Brain processing of a configural vs elemental odor mixture in the newborn rabbit

Abstract

Organisms are surrounded throughout life by chemically complex odors. How individuals process an odorant within a mixture or a mixture as a whole is a key question in neuroethology and chemical senses. This question is addressed here by using newborn rabbits, which can be rapidly conditioned to a new stimulus by single association with the mammary pheromone. After conditioning to ethyl maltol (odorant B), pups behaviorally respond to B and an A'B' mixture (68/32 ratio) but not to ethyl isobutyrate (odorant A) or an AB mixture (30/70 ratio). This suggests elemental and configural perception of A'B' and AB, respectively. We then explored the neural substrates underlying the processing of these mixtures with the hypothesis that processing varies according to perception. Pups were pseudoconditioned or conditioned to B on postnatal day 3 before exposure to B, A'B' or AB on day 4. Fos expression was not similar between groups (mainly in the olfactory bulb and posterior piriform cortex) suggesting a differential processing of the stimuli that might reflect either stimulus complexity or conditioning effect. Thus, the ratio of components in A'B' vs AB leads to differential activation of the olfactory system which may contribute to elemental and configural percepts of these mixtures. In addition, together with recent behavioral data, this highlights that configural perception occurs even in relatively immature animals, emphasizing the value of the newborn rabbit for exploration of odor mixture processing from molecules to brain and behavior.

Brain anatomy of the 4‐day‐old European rabbit

“…, ; Schneider et al. ,b). The study was carried out in accordance with ethical rules enforced by French law and was supported by ethical committee authorisation no.…”

“…In 4‐day‐old pups, it has been shown that the TT is differentially activated depending on the odour stimulus (Schneider et al. ). However, the role of this region remains to be investigated in greater detail in the rabbit.…”

“…, ; Schneider et al. ,b) and shows feeding‐entrained anticipatory metabolic activity in 7‐day‐old pups (Olivo et al. ).…”

“…; Schneider et al. ,b). Moreover, fMRI studies only show relatively low resolution images of the brain from 4 to 40 weeks after birth (Lim et al.…”

“…; Schneider et al. ), food anticipatory brain activity, circadian rhythm and sibling interactions (e.g. Caba & González‐Mariscal, ; Montúfar‐Chaveznava et al.…”