Quentin Perrenoud
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.
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.
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.
