IBENS - ENS

Quentin Perrenoud

Tommaso VILLA — 2026-03-02T11:22:59Z

The IBENS welcomes a new junior professor of Neuroscience starting on January 2026. Quentin Perrenoud will teach neuroscience at ENS and pursue his research on the function of neural rhythms in the cerebral cortex : our main cognitive center and a region that is crucially affected in major psychiatric disorders.

Quentin Perrenoud studied genetics at University Paris Cité before switching to neuroscience during his PhD. In the last decade at the University of Amsterdam and Yale University, he studied brain rhythms in the visual cortex with a focus on gamma waves : a pattern observed during active mental state that is disrupted in schizophrenia. While the mechanism and function of gamma waves have long eluded researchers his work revealed that gamma waves play an essential role in cortical processing and are intimately linked to the communication of the cerebral cortex with another brain structure : thalamus (https://doi.org/10.1038/s41586-025-09604-9).

The cerebral cortex is a recognizable folded layer of gray matter on the outer part of the brain (cortex means bark or husk in Latin). It is our main cognitive center and is crucial for perception, language, thoughts and all aspects of behavior. The expansion of the cortex during human evolution is largely believed to underlie the development of our intelligence. Cortical dysfunction is also at the heart of devastating psychiatric diseases such as depression, schizophrenia and autism. Thus, understanding the cortex appears as one of the challenges of modern neurosciences.

This is complicated by the intricate architecture of the cortical network : a distributed system composed of many areas specialized in sensory, motor or associative processing. Each area receives input from the thalamus, a central structure relaying not only sensory information from the periphery but also processed information from distant cortical and motor regions. Thalamic inputs are processed in the cortex by six layers of neurons projecting to specific cortical and subcortical structures. A remarkable and ubiquitous aspect of this organization is that it forms hierarchical processing stages (Fig. 1a). The power of such hierarchical organization is illustrated by the recent developments of artificial intelligence which uses hierarchical processing and took direct inspiration from the cortex. However, information flows in the thalamocortical hierarchy through a complex net of feedforward, feedback and parallel connections and the way information is dynamically routed through this network is not well understood.

Figure 1

a) Hierarchical processing in the visual parts of the cortex and thalamus : visual information from the retina is relayed by the thalamic dorsal geniculate nucleus (dLGN) and integrated through the layers of to the primary visual cortex (V1). Deep layer neurons in V1 send processed visual information to a secondary thalamic nucleus : the pulvinar (LP) which forwards it to higher order visual area (HVAs). Thus, information from restricted parts of the visual field is progressively integrated into higher order percepts such as objects and visual maps used in navigation. b) left : LFP recording across the layers of V1 showing the time of occurrence of neural events associated with gamma activity (i.e. gamma events, orange) ; right : current source density analysis (CSD) of the LFP around gamma events where current sinks (blue) correspond to areas where neurons become active. Gamma events coincide with activation propagating from layer 4 which receives input from dLGN to layers 2-3 and layer 5 which sends output to LP.

Recordings of the electric field generated by the cortex (also called local field potential, or LFP), reveal that cortical activity is highly dynamics and varies with behavior. Sleep is characterized by slow oscillations while wakefulness is associated with high frequency activity. Gamma waves (30-80Hz) are typically observed during active wakefulness and could reflect the activation of specific routes of the thalamocortical network. However, gamma waves have low intensity and wax and wane quickly in and out of existence. Thus, their detection has long relied on spectral analysis, an analytical tool that decomposes neural signals into specific frequency components. Spectral analysis is very sensitive but typically lack precision in time. Therefore, it has been difficult to track gamma activity precisely to understand its mechanisms.

A key idea of the work of Quentin Perrenoud is to approach gamma oscillation as specific neural events which, if singled out, can give us a lens into cortical computations. Taking advantage of modern multi-channel electrode arrays, Quentin developed a new method allowing to detect gamma waves with millisecond precision (https://github.com/cardin-higley-lab/CBASS?tab=readme-ov-file). Applying this method in the visual cortex revealed that gamma waves correspond to brief events of cascading thalamocortical synchrony lasting 15ms. Gamma events start in the thalamus and progress quickly through cortical layers bearing the mark of a feedforward pass of through the thalamocortical hierarchy (Fig. 1b). With optogenetics, a technique permitting to modulate neural activity with light, he either suppressed or evoked Gamma events artificially through briefs activation of the thalamus (Fig. 2). Strikingly, the suppression of gamma events impaired visual perception while artificial gamma events created illusory visual percepts. Finally, he showed that the rate of gamma events varies flexibly as a function of behavior and increase notably during visually informed decisions.

Figure 2

a) left : experimental design : dLGN is inhibited by optogenetic activation of the thalamic reticular nucleus (TRN) to shut down gamma events in V1 ; right : LFP recording and gamma events (orange) before (no background) and during dLGN suppression (green). b) left : experimental design : dLGN terminals are optogenetically activated to trigger gamma events in V1 ; right : CSD showing the time course of optogenetically triggered gamma events.

Quentin's work clarifies the mechanisms of gamma activity and introduces a new methodology to study cortical rhythms. At IBENS, Quentin will study how gamma shapes visual representation at all processing stages of the cortical hierarchy and investigate how gamma events are dynamically modulated with behavior in health and disease. He will also investigate if other patterns may be described in other functional regions of the cortex and thalamus. In particular, he will collaborate with the team Neurophysiology of Brain Circuit directed by Clément Léna and Daniéla Popa (https://www.ibens.bio.ens.psl.eu/spip.php?rubrique53) to investigate how rhythm in the sensory and motor regions of the cortex and thalamus integrate instructions coming from the cerebellum to guide motor output.

Ymetry

Frédérique Godfroid — 2022-01-24T12:59:31Z

Spin-off from PSL University, YMETRY has been created to serve the international research community with its new and innovative technology developed in the Institute of Biology of the Ecole Normale Supérieure (IBENS, CNRS UMR8197, INSERM U1024).

YMETRY develops and manufactures its patented custom head fixing devices and scientific instruments for in-vivo scientific research. YMETRY devices use a patented 3D design and 3D-printing in Titanium to provide uniquely both rigidity and lightness at low cost. New customized devices can be easily designed to be adapted to different models and brain areas and to integrate multiple measurement / actuactor technologies.

More information and details

Karthala System

Frédérique Godfroid — 2019-04-24T09:38:38Z

Spin-off de l'IBENS, KARTHALA System met à la disposition de la communauté scientifique des microscopes de haute technologie permettant de lire et de modifier l'activité biologique au sein des tissus vivants à très grande vitesse. KARTHALA System s'appuie sur une technologie innovante de mise en forme de la lumière, l'interaction acousto-optique, plus agile que les méthodes mécaniques classiques utilisant des miroirs mobiles. Le premier produit de Karthala System est un microscope bi-photonique digital rapide, l'AODscope.

Des outils au cœur de la révolution optogénétique

Les deux dernières décennies ont vu le progrès spectaculaire des outils moléculaires permettant d'utiliser la lumière pour mesurer (rapporteurs) ou modifier (actuateurs) l'activité physico-chimique des tissus biologiques de manière minimalement invasive. Cette approche photonique a pris son plein essor avec le développement de rapporteurs et d'actuateurs génétiquement encodés, dérivés de protéines fluorescentes et de photo-senseurs naturels. Ces méthodes optogénétiques permettent d'enregistrer et de contrôler optiquement l'activité biologique de cellules génétiquement identifiées, y compris leur activité électrique. La photochimie et l'optogénétique bouleversent donc tous les domaines de la biologie.

Le potentiel de la révolution optogénétique ne pourra être exploité pleinement qu'avec le développement de technologies photoniques souples et robustes permettant d'adresser la lumière au bon endroit et au bon moment. Les techniques de microscopie optique traditionnelles, qui ont été conçues pour l'acquisition d'images, sont lentes et inadaptées. Les microscopes conçus par KARTHALA System ont pour ambition de promouvoir une nouvelle façon de manier la lumière, permettant d'accéder spécifiquement aux zones de l'échantillon dans lesquels l'information doit être lue ou inscrite, de manière ciblée et extrêmement rapide. KARTHALA System s'est fixé pour défi d'atteindre une capacité d'adressage d'un million de voxels par seconde dans un volume de 1 mm3.

Les neurosciences constituent le cœur de cible de KARTHALA System. Comprendre le cerveau dans son fonctionnement normal et pathologique est un enjeu à la fois intellectuel et de santé publique. Ce défi fait l'objet de deux grandes initiatives internationales : le "Human Brain Project" financé par l'Union Européenne dans le programme cadre Horizon 2020 (2014-2020) et la "Brain Research through Advancing Innovative Neurotechnologies" (BRAIN), initiative initiée en 2013 par l'administration Obama. Comme l'indique l'intitulé du projet BRAIN, les avancées en neurosciences passent par le développement de nouvelles technologies, en particulier celles permettant d'enregistrer et de modifier l'activité des cellules nerveuses, les neurones, pendant le fonctionnement cérébral. Les microscopes développés par KARTHALA System sont à même de répondre à ce défi en fournissant une vitesse d'adressage adaptée à la bande passante du traitement de l'information dans le cerveau.

KARTHALA system, jeune compagnie fondée en mars 2017, est dirigée par Thomas Oksenhendler, un physicien expert en laser de puissance et interactions acousto-optiques. La compagnie s'appuie sur plus de 15 années de développements dans le domaine de la microscopie multi-photonique acousto-optique au sein de l'IBENS, en collaboration entre Benjamin Mathieu, le responsable de la plateforme d'imagerie, et les équipes de Laurent Bourdieu et de Stéphane Dieudonné.
KARTHALA System bénéficie d'un transfert de technologie, de propriété intellectuelle et de savoir-faire depuis les équipes de l'IBENS, dans le cadre d'un concours scientifique géré par INSERM transfert. Cette longue période de maturation, associée à un effort de prototypage et de dissémination, ont permis de concevoir un instrument robuste, l'AODscope, validé auprès des utilisateurs. Une première version de cet instrument a été installée en 2010 au "Cervo Brain Research Centre" / Université Laval à Québec, puis dupliquée en 2012 à la plateforme d'imagerie de l'IBENS. L'AODscope a produit depuis 10 publications de haut niveau. Une nouvelle génération de microscopes permettant l'adressage volumique et optimisant la profondeur de pénétration sont déjà à l'étude.