Inhibitory mechanisms and circuits in the hippocampus

Simon Chamberland, PhD 
Pathway to Independence Fellow
New York University School of Medicine
NYU Neuroscience Institute
New York, NY, USA

This conference is part of the the IRCM Early-Career Scientist Seminar Series (ECS3), a groundbreaking initiative whose mission is to showcase early career scientists. This is a great opportunity to discover the exciting projects of these researchers in training in front of a multidisciplinary audience.

---

In person : 
IRCM Auditorium
110, avenue des Pins O, H2W 1R7 Montreal
Wearing a mask is mandatory at all times

Online :
Zoom link : https://zoom.us/j/95269762104
ID : 952 6976 2104
Code : 476372

IRCM conferences are set to occur under a hybrid format. However, please note that last-minute changes to online-only lectures may occur due to unforeseen circumstances. We invite you to visit this webpage again a few days before attending.

---

About this conference : 
I will present our findings on inhibitory circuits in health and disease. I will show that the firing of hippocampal fast-spiking interneurons is persistently interrupted by brief synaptic inhibition, resulting in a prolonged disinhibitory window. Combined genetic and functional dissection of the hippocampal GABAergic interneuron architecture revealed that the interruption of firing is mediated by a previously unknown subpopulation of interneurons. Finally, I will show how the anti-seizure molecule cannabidiol acts on these circuits to restore physiological activity.

About Simon Chamberland : Dr. Simon Chamberland obtained his PhD in Neurosciences from Université Laval and then joined the lab of Dr. Richard Tsien at New York University to pursue a postdoctoral fellowship. In 2021, he became a K99/R00 Pathway to Independence Fellow and continued his research work under the mentorship of Dr. Tsien and Dr. György Buzsáki. Dr. Chamberland is an exceptional early-career scientist with an impressive record of publications, funding, awards and engagement within the scientific community. He has been invited to give lectures in several countries across the world, including Italy, Spain and Malaysia.

Interview with Dr. Chamberland

Question

Please tell us about your career path, leading up to your application to the Early-Career Scientist Seminar Series

Réponse | Answer 

“Over the last 12 years, I have investigated the fundamental elements regulating synaptic transmission, neuron biophysics, and neuronal networks with the aim of understanding how neuronal circuits support information processing. As a PhD student in the lab of Dr. Katalin Tóth at Université Laval (Quebec City), I disentangled the presynaptic elements enabling synaptic function in hippocampal mossy fibers. My work uncovered a new mode of information transfer in the central nervous system. Following my graduate studies, I felt strongly about leveraging the tools I had previously used towards a more global understanding of neuronal networks ranging from ion channel biophysics to neuronal interactions. I had this exact opportunity as a postdoctoral fellow in the laboratory of Dr. Richard W. Tsien (New York University School of Medicine), where I have identified a novel form of persistent activity that silences fast-spiking interneurons to strongly disinhibit principal neurons. We found that brief and minimal synaptic inhibition persistently interrupts the firing of fast-spiking interneurons for hundreds of milliseconds. Our experimental and computational modeling results agree that the persistent interruption of firing is a refractory state maintained by the gradual inactivation of a potassium current. These findings reveal for the first time that the apparently robust non-accommodating firing of fast-spiking interneurons is easily disrupted by minimal synaptic inhibition, which opens novel avenues of research to understand how disinhibition contributes to synchronize neuronal networks.”

Question

Please tell us about your passion for research. What motivates you most about your work? 

Réponse | Answer 

“Neurons and their circuits provide the substrate for information processing in the brain and allow us to interact with our environment. Neurons are intrinsically beautiful. Their branched structures can be traced over long distances in the brain. Decades of research has shown that these branched structures enable the input-output function of neurons. Yet, the circuits that they form are incompletely understood. I am fascinated by how neurons are assembled and coordinated to support cognitive functions, and how this coordination is disrupted in neurological disorders. Billions of entangled neurons populate the human brain, but neurons are not all the same. In the cortex, approximately 300 subtypes of neurons co-exist in a tight space. I am motivated by gaining an understanding of how cognitive functions emerge from these neuronal circuit. I want to dissect the role of individual neuron types in supporting cognitive functions. Part of my motivation comes from obtaining a better understanding of neurological disorders. This is because many neurological disorders still lack effective treatment options. We believe that gaining a better understanding of neuronal circuits is crucial to understand how they are dysregulated in diseases.”

Question

Please tell us about your professional goals. What do you hope to accomplish as a scientist?

Réponse | Answer 

“I aim to lead a research program and contribute to train the next generation of scientists. The overarching goal of my research is to understand how a diverse population of neurons interconnected by specialized synapses are coordinated to process information. Recent research has highlighted the extensive genetic diversity of neurons, providing an atlas of the different neuronal populations. Our latest results demonstrated that at least part of this genetic diversity is translated to functional diversity. What are the functions of multiple and diverse neuronal populations? Why is there a need for such neuronal diversity in the brain? How can these neurons be manipulated to restore physiological activity in neurological disorders? These questions have been driving my research efforts for the last years. Recent developments now offer the opportunity to understand neuronal subtypes from a functional standpoint, which I believe is key to understanding the brain in physiological and pathological conditions.”

To make sure you don't miss any of the IRCM conferences, sign up now for our newsletter!