SPLTRAK Abstract Submission
Role of adult-born versus preexisting neurons in olfactory perception in a complex olfactory environment in mice.
Jeremy Forest1, Laura Chalenšon1, Maellie Midroit1, Claire Terrier1, Isabelle CaillÚ2, Joelle Sacquet1, Claire Benetollo1, Killian Martin1, Marion Richard1, Anne Didier1, Nathalie Mandairon1
1UMR 5292 CNRS CRNL, Lyon, France
23Sorbonne UniversitÚs, UniversitÚ Pierre et Marie Curie Univ Paris 06, Centre National de la Recherche Scientifique UMR8246, INSERM U1130, IBPS, Neuroscience, Paris, France

Olfactory perceptual learning is defined as an improvement in the discrimination of perceptually close odorants after passive exposure to these odorants. In mice, simple olfactory perceptual learning involving the discrimination of two odorants depends on an increased number of adult-born neurons in the olfactory bulb, which refines the bulbar output. However, the olfactory environment is complex raising the question of the adjustment of the bulbar network to multiple discrimination challenges. Using habituation/cross habituation task, we found that perceptual learning of one to six pairs of similar odorants led to discrimination of all learned odor pairs. The assessment of adult-born neurons density in the olfactory bulb showed that increasing complexity did not increase adult-born neuron survival but enhanced the number of adult-born neurons responding to learned odorants. To better understand the increased functional recruitment of adult-born neurons with perceptual learning complexity, we looked for associated structural modifications in these neurons. To this aim, we injected lentivirus expressing GFP at P60 and revealed that spine density is increased with increasing complexity. On same animals, lentivirus expressing DsRed was injected at P0 in order to label preexisting neurons (neurons born during the ontogenesis of the granule cell layer in the early post-natal days). Interestingly, only complex learning induced morphological changes in preexisting neurons. Selective optogenetic inactivation of either population performed in freely moving mice confirmed functional involvement of adult-born neurons regardless of the enrichment complexity while preexisting neurons were required for complex discrimination only.