Pinpointing the neural mechanisms that support the remarkable visual fidelity of visual recognition memory

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We have all had the perplexing experience of seeing someone and remembering that we know them, but not being able to recall any other details, such as who they are or how we know them. In those moments, sometimes all that we can remember is that a person is familiar to us. This highlights a difference in recognition memory between familiarity memory and more detailed recollection memory. We rely on familiarity memory every day to remember whether we know specific people and things. Despite how important this type of memory is, we still do not understand how familiarity memory works in our brains, although previous studies have suggested that it may utilize a different brain network than recollection memory. Understanding familiarity memory will help us develop therapeutic approaches to treat memory disorders such as Alzheimer’s disease and other types of dementia. It could also help us create more effective educational tools to enhance learning in children and adults. This project seeks to understand how different parts of the brain help us remember whether we’ve seen something before. To figure this out, this project focuses on the question: how different does a picture have to be for us to know that it’s different from an image that we remember seeing before? This project compares the pattern of brain activation during accurate familiarity memory with brain activity during confusions in familiarity memory, in order to determine precisely what brain regions are involved in supporting familiarity memory and in order to deepen our understanding of the neural basis and architecture of recognition memory. More specifically, this cross-species study focuses on understanding how a network of key brain regions, believed to play a role in memory, including inferotemporal cortex, perirhinal cortex, entorhinal cortex and the hippocampus contribute to visual recognition memory. The research explores this question in the context of a Mnemonic Similarity task, which probes the ability of humans and monkeys to distinguish novel and familiar images in the presence of lure images that are similar to images that have already been seen. Aim 1 focuses on quantifying how often humans and monkeys falsely remember seeing images as a function of how similar that the images are. Aim 2 focuses on the neural basis of familiarity memory and investigates how neuronal cell and ensemble activity in monkey inferotemporal cortex, perirhinal cortex, entorhinal cortex and the hippocampus compare with one another and correlate with memory behavior. Together, these results will, for the first time, describe the differential and collective contributions of these brain areas to shaping visual familiarity and the visual detail of visual recognition memory.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.