Multidimensional memory topography in the medial parietal cortex identified from neuroimaging of thousands of daily memory videos.

Our memories form a tapestry of events, people, and places, woven across the decades of our lives. However, research has often been limited in assessing the nature of episodic memory by using artificial stimuli and short time scales. The explosion of social media enables new ways to examine the neural representations of naturalistic episodic memories, for features like the memory's age, location, memory strength, and emotions. We recruited 23 users of a video diary app ("1 s Everyday"), who had recorded 9266 daily memory videos spanning up to 7 years. During a 3 T fMRI scan, participants viewed 300 of their memory videos intermixed with 300 from another individual. We find that memory features are tightly interrelated, highlighting the need to test them in conjunction, and discover a multidimensional topography in medial parietal cortex, with subregions sensitive to a memory's age, strength, and the familiarity of the people and places involved.