How is learned information stored in the brain and how does it interact with the innate representations to enable adaptive behaviour? The result of plasticity that accounts for a given memory can be broadly referred to as an engram. In recent years, the term engram has been operationalized as an ensemble of cells that is activated by a learning experience, undergoes plasticity, and enables specific memory recall. Engram labelling methodologies are now opening new avenues for investigating how learned and innate representations are behaviourally expressed.

In this seminar, I will introduce the background of the broader memory engram field. I will describe how engram cell labelling methodologies allow us to genetically label, observe, and manipulate the specific ensembles of neurons that encode particular memories in the rodent brain. I will then describe our recent research on innate and acquired forms or long-term forgetting in the mouse, by focussing on natural forgetting in adults and infantile amnesia during development. I will outline a novel framework that considers both natural and pathological forgetting to be predictive processes that involve the interaction of a subject’s priors with perceptual experience. I will introduce a perspective whereby instincts can be conceived as innately constructed ensembles that can functionally interact with memory engrams. Finally, I will describe our recent research into how engrams formed under thermal challenges can influence brain-body interactions to regulate whole body metabolism.