Research 

Research Overview

My program of research focuses on understanding the neural basis of olfactory perception and how olfactory perception is modulated by learning and normal or pathological aging. We are also interested in how olfaction can modulate affective function such as anxiety. 

Research 

Odorants play an important role in many aspects of life such as social interactions (mother–infant attachment, sexual behavior), navigation, alarm signals detection and recognition (smoke, rotten food, predators), or food intake. I am investigating how the brain responds to olfactory experiences in order to guide the behavior. To achieve this, we use a variety of methods ranging from behavioral tests, optogenetics, brain imaging, morphological 3D analysis of neurons… 

The main ongoing projects: 

1- Understanding the neural basis of odor hedonics

One major aspect of olfactory perception is hedonics. Indeed, as you smell an odorant, your first reaction will certainly be either I like or I dislike this smell. This primary function of olfaction guides approach or avoidance to stimuli. We investigate how our brain dictates us to like and thus approach an odorant. We reported that the olfactory bulb, the first cortical relay of olfactory information processing, carries a neural signature of odor hedonic value. We are now investigated in how this hedonic information is processed in higher olfactory centers and reward system to drive behavior. We also study how the  experience-dependent changes in hedonic value are encoded in the olfactory pathway. 

Impairments in odor hedonics with normal aging may affect quality of life in a way that is not anecdotal. They affect social interactions, impair hedonic responses to food odors and decrease the pleasure of eating and food intake. This can lead to social isolation and bodily wasting disorders (common in aging and age-related dementias) and represents a major public health problem. We are working on the mechanisms responsible for the alteration of brain odor hedonics with aging. 

2- Why the odor of Rose is such attractive? 

Roses have been domesticated since Antiquity for their perfume. Greeks, Romans, Persians, and Chineses grow roses since at least 2000 years. All over the world, no other plant has followed the human history for this hedonic reason. Indeed, this is the only example of plant domestication for the human delight, all the others being domesticated for food (rice, corn, wheat…). For the plant itself, this is an evolution success. So why the odor of roses is able to induce such strong positive emotional reaction? Why and how our brain dictates us to like rose perfume? In this project, we investigate the odorant molecules that are the most attractive in the rose odor and we will look for whether the reward circuit is involved in odor attractiveness. 

3- Understanding the neural mechanisms underlying odor impairment by early life adversity

A major risk factor of depression in adults is childhood trauma. Indeed, neglect early in life causes developmental brain disorders that have a long term effect on the emotional state. There is a mouse model that mimics this pathology: the model of early life adversity induced by maternal separation. In this project, we will investigate the neural bases underlying impairments in olfactory perception after early life adversity-induced depression in mice. 

4-Understanding the role of adult born neurons in different olfactory learning as well as feedback projections.

Implicit and explicit learning paradigms have been shown to lead to similar behavioral outcomes in many cases, and are often thought to be governed by separate neural circuits. The olfactory system presents a unique opportunity to directly compare the neural circuits mediating these two types of learning, since both have been shown to rely on changes in olfactory bulb processing. The overall goal of this project is to determine how different neural representations induced by different behavioral paradigms could lead to similar improved in discrimination. We here propose an interdisciplinary collaborative approach to study the neural mechanisms underlying implicit and explicit discrimination learning in the olfactory bulb. The overall hypothesis of this work is that the different neural representations induced by explicit and implicit learning are at least partially due to differential integration of adult born interneurons and engagement of cortical feedback projections.

5- The "Proust effect": how do olfactory memories of childhood persist in adults? 

In "Du côté de chez Swann", Marcel Proust describes the joy and memories of childhood evoked by the smell of a madeleine dipped in a linden infusion. It seems that autobiographical memory of smells is older, i.e. goes back further in childhood, than memory of other sensory cues such as sight or hearing, and is most often associated with positive events. This project has two main objectives. Firstly, we are setting up a participatory survey with national and then international scope, in order to study on a large scale the age of the first olfactory memories, their positive character and the associated context. Then, to understand how these olfactory memories are created in childhood and maintained in adults, we will develop an animal model of positive autobiographical olfactory memory. This project will provide a better understanding of how the brain underpins the persistence of this powerful early olfactory memory.

Collaborators 

Dr. Kevin Bath (Columbia Univ.)

Drs. Sylvie Baudino and Jean-Claude Caissard (Univ. Jean Monnet)

Dr. Christiane Linster (Cornell Univ.)

Dr. Olivier Raineteau (SBRI)

Dr. Nicolas Renier (ICM) 

Dr. Dan Wesson (Univ. of Florida)

Dr. Pierre-Hervé Luppi (CRNL)

Dr Jérome Brunelin (CRNL)

Research supported by

CNRS; Inserm; Lyon 1 University; Région Rhône Alpes (APP Ambition Recherche), Labex Cortex, NrJ Fondation, IRP CNRS, FRM, B2V, ANR