TY - JOUR T1 - Human hippocampal theta oscillations reflect sequential dependencies during spatial planning JF - bioRxiv DO - 10.1101/372011 SP - 372011 AU - Raphael Kaplan AU - Adrià Tauste Campo AU - Daniel Bush AU - John King AU - Alessandro Principe AU - Raphael Koster AU - Miguel Ley-Nacher AU - Rodrigo Rocamora AU - Karl J. Friston Y1 - 2018/01/01 UR - http://biorxiv.org/content/early/2018/07/19/372011.abstract N2 - Movement-related theta oscillations in rodent hippocampus coordinate ‘forward sweeps’ of location-specific neural activity that could be used to evaluate spatial trajectories online. This raises the possibility that increases in human hippocampal theta power accompany the evaluation of upcoming spatial choices. To test this hypothesis, we measured hippocampal oscillations during a spatial planning task that closely resembles a perceptual decision-making paradigm. In this task, female and male participants searched visually for the shortest path between a start and goal location in novel mazes that contained multiple choice points, and were subsequently asked to make a spatial decision at one of those choice points. During the search/planning period, we observed ~3-6 Hz hippocampal theta power increases that were negatively correlated with subsequent decision speed, where decision speed correlated with choice accuracy. Notably, hippocampal theta power increases were preferentially induced by planning in mazes containing a sequence of choices that were initially straightforward and subsequently ambiguous. These results implicate the hippocampal theta rhythm in the searches of deep decision trees, with a particular ‘bottleneck’ form.Significance Statement Low frequency (~<10 Hz) hippocampal theta oscillations are putatively linked with learning and decision-making in rodents, but how hippocampal theta relates to specific decision processes is unclear. Here, we tested human volunteers on a spatial planning paradigm that discloses the role of the hippocampal theta rhythm when planning sequential choices in novel environments. Recording from the human hippocampus, we find that increased hippocampal theta power correlates with planning quicker and more accurate spatial decisions. Furthermore, hippocampal theta power increased during planning in mazes with choice sequences that were initially straightforward and subsequently ambiguous. These results implicate the human hippocampal theta rhythm in the evaluation of demanding upcoming spatial choices.The research was supported by a Sir Henry Wellcome Postdoctoral Fellowship to RKa (Ref: 101261/Z/13/Z) and a Wellcome Principal Research Fellowship to KJF (Ref: 088130/Z/09/Z). We thank Carmen Pérez Enríquez for helpful discussion and the staff at Hospital del Mar for help with patients. We would also like to thank David Bradbury and Letty Manyande for assistance with MEG experimental setup. We also thank the Wellcome Centre for Human Neuroimaging for providing facilities. ER -