Goal-dependent Integration and Differentiation of Hippocampal Representations.

Poster Session C - Sunday, April 14, 2024, 5:00 – 7:00 pm EDT, Sheraton Hall ABC

Eleonora Ghiraldini¹ (eleonoraghiraldini97@gmail.com), Stefani Morgan¹, Sophie D. Allen², Emma Tripp², Chris B. Martin^1,2; ¹Program in Neuroscience, Florida State University, ²Department of Psychology, Florida State University

Evidence from prior neuroimaging studies suggests that hippocampal representations of prior experience are not fixed. Indeed, different studies report different degrees of pattern similarities across stimuli that share the same context: a similarity increase, an orthogonalization, or a similarity decrease. A possible explanation for these different results is that hippocampal representations are expressed in a goal-dependent manner, such that activity profiles appear integrated when retrieving general information and differentiated when retrieving specific experiences. We aimed to test this hypothesis using functional magnetic resonance imaging (fMRI) in young adults. Participants initially watched two episodes of the sitcom Seinfeld during an unscanned encoding stage. They then completed a cued recall task during a subsequent scanning session in which they had to recollect previously encoded information at varying levels of detail: specific scenes (event condition), narratives of one character in one episode (narrative condition), or the main plot of one episode (episode condition). The cues were sentences presented visually and were the same across the different conditions. Thus, we systematically biased retrieval toward either episodic gist or event-specific detail while holding the cues constant. We will use representational similarity analysis to quantify the degree of integration/differentiation within each condition. We expect retrieval-related activity in the hippocampus to be maximally integrated in the episode condition and maximally differentiated in the scene condition. We anticipate an intermediate response profile in the narrative condition. Preliminary analyses of pilot data from two subjects suggest different activation profiles across conditions.

Topic Area: LONG-TERM MEMORY: Episodic