Ripple oscillations in the healthy and epileptic brain: local origin and large-scale impact

Abstract: The brain is a highly interconnected dynamical system that relies on synchronous oscillations to coordinate neuronal activity within and across brain areas, a process believed to be essential for most cognitive functions in the healthy brain. In epilepsy, neuronal ensembles become over-synchronized, leading to cognitive impairment and loss of consciousness. In this lecture, I will first present an overview of “ripples” and “fast ripples”, high frequency oscillations (>150Hz) that play a key role in memory formation in health and is a potential biomarker of the epileptogenic zone in epilepsy. I will then present recent findings from our lab regarding the role of the thalamus in the coordination of ripples with global forebrain dynamics. Next, using a novel hybrid micro- macro-wire depth electrode in epileptic patients, which include two or three tetrodes enabling to each record up to 10 neurons in local circuits, we have characterized the local (i.e. in the epileptic zone) and global (on other depth electrodes) response of neurons to pathological fast ripples during interictal epileptic discharges. While fast ripples are associated with increased neuronal activity in local circuits only, they are followed by inhibition in large-scale networks. These findings suggest that thalamocortical inhibition is a fundamental refractory process for forebrain networks, certainly preventing the propagation of epileptiform activity to healthy tissue.

Brief Bio: After graduating in physics from ESPCI ParisTech, Adrien Peyrache studied cognitive science in a joint MSc program at Pierre and Marie Curie University and Ecole Normale Supérieure (Paris, France). In 2009, he completed his PhD in neuroscience at the Collège de France. His thesis focused on the neuronal mechanisms of sleep-dependent learning and memory. After a year of postdoctoral training with Alain Destexhe at the CNRS (Gif-sur-Yvette, France) where he studied the coordination of neuronal activity during sleep, he moved to the laboratory of György Buzsaki at New York University Neuroscience Institute. There, he showed that neuronal activity in the spatial navigation system during sleep is indistinguishable from wakefulness, revealing how it is governed by neuronal circuits and dynamics. In 2016, he started his lab at Montreal Neurological Institute, McGill University. His research focuses on unraveling the neural basis of spatial cognition and memory formation. Adrien Peyrache is an active advocate of Open Science. He is one of the founding members and current chair of the Open Science In Action Prize. Adrien Peyrache has received several recognitions for his work, including a Human Frontiers Science Program postdoctoral fellowship and NIH K99 award. He currently holds the Canadian Research Chair in Systems Neuroscience.

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Topic: KCN Event: Adrien Peyrache

Time: May 27, 2021 10:00 Eastern Time (US and Canada)

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