Sophie Allen: Replaying Autobiograhical Memories with HippoCamera

My name is Sophie Allen, and I am a junior studying Psychology and Biomathematics. For the past two and a half years I have been involved in long-term memory research in Dr. Chris Martin’s Memory Lab in the Department of Psychology. Throughout my time in the Martin Memory Lab, I have been given opportunities to work independently on projects that have challenged me and allowed me gain deeper knowledge about the field of cognitive neuroscience. Finding my particular interests in memory research has led me to develop questions of my own. The research project I have been awarded the IDEA Grant, allows me to investigate whether memories are represented differentially in the hippocampus in a younger adult population and if memories drift back together after a delay or remain separated in the hippocampus.

Sophie Allen, Senior, Psychology

Recalling our past experiences shapes the perception of our present self and influences our thoughts about the future, thus contributing to our sense of self. Our ability to recall specific experiences requires the integration of semantic memory (general knowledge about the world), and episodic memory (specific details about an event). For example, retrieving the memory of your high school graduation requires the semantic knowledge of receiving a diploma, but it also requires the retrieval of event specific details, like seeing the look on your mom’s face as you walk on stage. This type of memory composed of both event-specific details and general knowledge is known as autobiographical memory. Our ability to recollect event-specific autobiographical details contributes to how vividly we can reexperience a moment from our past. As we age, our ability to recall semantic knowledge about an event stays constant throughout our lives, but retrieval of specific details of an event tend to decline with age.

Although this decline is common even among neurologically healthy, aging individuals, there have been very few interventions aimed at the decline in episodic details in autobiographical memories. Recent work by my mentor, Dr. Martin aimed to improve event specific details in autobiographical memories in older adults through a smartphone application called HippoCamera. His work demonstrated that using HippoCamera improved episodic recollection in older adults. Additionally, using the application to repeatedly reactivate autobiographical memories also reduced similarities among event-specific memory traces in the hippocampus during retrieval, meaning pattern-separation in the hippocampus was associated with enhanced episodic recollection.

My summer research project will be conducted in Toronto, Ontario under the mentorship of Dr. Martin and Dr. Morgan Barense, who is a professor at the University of Toronto and was a collaborator on the original work with HippoCamera. In Toronto I will build on the prior results using behavioral and neuroimaging data in a younger adult population. Specifically, I will investigate whether using HippoCamera differentiates hippocampal memory traces in younger adults as it did in geriatric populations. Moreover, I will also characterize the durability of any potential neural differences by asking whether they persist well after discontinuation of HippoCamera use.

To answer the proposed questions, I will use functional magnetic resonance imaging (fMRI) data obtained at two different time points in healthy young adults. For the first part of the experiment, participants were asked to use HippoCamera to record and replay autobiographical memory cues for a consecutive ten weeks. Each memory cue was either viewed during replay sessions (replayed condition) or never viewed during replay sessions (baseline condition). fMRI data were collected seven days after ten-weeks using the app, and again after a three-month delay. Three-month follow-up fMRI data were not obtained in the previous study conducted in older adults. Having fMRI data from two separate timepoints will allow me to determine whether any representational changes in the hippocampus persist after the three-month delay.

For both sessions, each trial of the fMRI task included three components. First, participants watched one of their previously recorded autobiographical memory cues. Second, they were asked to mentally relive the cued event. Third, they completed an episodic probe task that required a “yes/no” judgement about whether a word that appeared on the screen captured an episodic detail of the cued event. Data from both sessions will be analyzed to quantify the stability of the memory traces over time. We hypothesize there to be an initial increase in differentiation for the cues in the replayed condition from the first sessions. Furthermore, we hypothesize that the memories will remain separated, and to the extent that they are well remembered, we further predict that the memories would drift further apart.

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