PT  - JOURNAL ARTICLE
AU  - Rose A. Cooper
AU  - Maureen Ritchey
TI  - Progression from feature-specific brain activity to hippocampal spatial binding during episodic encoding
AID  - 10.1101/735761
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 735761
4099  - http://biorxiv.org/content/early/2019/08/15/735761.short
4100  - http://biorxiv.org/content/early/2019/08/15/735761.full
AB  - The hallmark of episodic memory is recollecting multiple perceptual details tied to a specific spatial-temporal context. To remember an event, it is therefore necessary to integrate such details into a coherent representation during initial encoding. Here we tested how the brain encodes and binds multiple, distinct kinds of features in parallel, and how this process evolves over time during the event itself. We analyzed data from 27 subjects who learned a series of objects uniquely associated with a color, a panoramic scene location, and an emotional sound while fMRI data were collected. By modeling brain activity at event onset and event offset, we were able to test how the neural signatures of individual features as well as the integrated event changed over the course of encoding. We observed a striking dissociation between early and late encoding processes: left inferior frontal and sensory signals at event onset tracked the amount of detail subsequently recalled and were dissociable based on distinct remembered features. In contrast, memory-related brain activity shifted to the left hippocampus at event offset, which was particularly sensitive to binding item color and sound associations with spatial information. These results provide evidence of simultaneous feature-specific neural responses at the start of episodic encoding that predict later remembering and show that the hippocampus acts to integrate these features into a spatially-coherent experience at an event transition.SIGNIFICANCE STATEMENT Understanding and remembering complex experiences is crucial for many socio-cognitive abilities, including being able to navigate our environment, predict the future, and share experiences with others. Probing the neural mechanisms by which features become bound into meaningful episodes is a vital part of understanding how we view and reconstruct the rich detail of our environment. Our findings show a functional dissociation between initial encoding processes, engaging lateral frontal and sensory regions to prioritize event features, and later encoding processes that recruit hippocampus to embed these features within a contextual framework. Identifying the mechanisms of complex event encoding is an important step toward understanding why many neurological and psychiatric disorders exhibit differences in how the world is perceived and remembered.