Conférence Forgetting : Marius Rosier "Dendritic Ih current modulates cortical engram excitability and memory recall"

Abstract: The ability to associate stimuli and create a memory is one of the most fundamental functions of the brain. Research from the past decade
has revealed that memory is encoded in sparse neuronal networks that are active during learning called engram cells. Although the cortex is recognized as
playing an important role in memory, the biophysical properties of cortical engram cells in sensory areas are largely unknown. To address this, we tagged
engram cells in the auditory cortex during tone fear conditioning and compared their dendritic and somatic properties with neighbouring non-engram cells.
Ex vivo patch-clamp recordings illustrated that engram cells had decreased excitability due to a transient increase in Ih current and were preferentially
connected with neighbouring engram cells. Using two-photon calcium imaging, we show that tuft dendrites of engram cells had dampened, but
synchronous, activity during recall which was preferentially increased by pharmacological block of Ih. Finally, Ih block increased freezing to the conditioned
stimulus, showing a causal link between this form of plasticity and memory recall. Together, these findings reveal Ih-driven intrinsic plasticity which leads to
specific information processing in engram cells and effects memory recall.