RT Journal Article
SR Electronic
T1 Structuring Time in Human Lateral Entorhinal Cortex
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 458133
DO 10.1101/458133
A1 Jacob L.S. Bellmund
A1 Lorena Deuker
A1 Christian F. Doeller
YR 2018
UL http://biorxiv.org/content/early/2018/12/20/458133.abstract
AB Episodic memories consist of event information linked to spatio-temporal context. Notably, the hippocampus is involved in the encoding, representation and retrieval of temporal relations that comprise a context (Deuker et al., 2016; Tubridy and Davachi, 2011; DuBrow and Davachi, 2014; Ezzyat and Davachi, 2014; Hsieh et al., 2014; Jenkins and Ranganath, 2010, 2016; Kyle et al., 2015; Lositsky et al., 2016; Nielson et al., 2015; Copara et al., 2014), but it remains largely unclear how coding for elapsed time arises in the hippocampal-entorhinal region. The entorhinal cortex (EC), the main cortical input structure of the hippocampus, has been hypothesized to provide temporal tags for memories via contextual drift (Howard and Kahana, 2002; Howard et al., 2005). Recent evidence demonstrates that time can be decoded from population activity in the rodent lateral EC, putatively arising from the integration of experience (Tsao et al., 2018). Here, we asked how learning a temporal structure influences entorhinal event representations. Participants acquired knowledge about temporal and spatial relationships between object positions—dissociated via teleporters—along a fixed route through a virtual city. We analyze fMRI multi-voxel pattern similarity change from before to after learning in the EC. Object representations in the anterior-lateral EC (alEC) specifically, the human homologue of rodent lateral EC (Navarro Schröder et al., 2015; Maass et al., 2015), changed to reflect elapsed time between events. Holistic representations of the temporal structure in alEC related to memory recall behavior suggesting mental traversals of the route during retrieval. Furthermore, we reconstructed the temporal structure of object relationships from alEC pattern similarity change. Our findings demonstrate that the experienced temporal structure of events shapes representations in the alEC, potentially via the reactivation of temporal context representations derived from slowly-varying population signals during learning. This provides novel evidence for the role of the human lateral EC in representing time for episodic memory.