The goal of this project is to determine the neural basis of the spatial and temporalcomponents that comprise human episodic memory and navigation. Damage to thehuman hippocampus results in significant impairments to both episodic memory andnavigation yet the commonalities behaviorally and neurally remain unclear. Wehypothesize that spatial and temporal contextual representations which in turn includetemporal order and interval underlie episodic memory and navigation in both partiallyoverlapping and unique manners. To understand how the hippocampus codes spatialand temporal context Aim 1 focuses on employing high-resolution hippocampalfunctional magnetic resonance imaging (fMRI) and intracranial encephalography (iEEG)to better understand the specific contributions of the microcircuitry of the humanhippocampus. Building on experiments and a model we have developed in the pastfunding period we hypothesize that hippocampal subfields CA3/DG play a role indifferentiation of spatial vs. temporal context while CA1 plays a role in integratingcommonalities across these two different forms of context. High-resolution hippocampalfMRI experiments directly test these ideas by employing a combination of experimentaldesigns to tease apart spatial and temporal processing coupled with multivariate patternanalyses (MVPA) to map hippocampal distributed codes for these behavioralcomponents. Hippocampal iEEG experiments focus on understanding how low-frequencies oscillations code both spatial distance and temporal contexts particularlytemporal intervals which we hypothesize relates primarily to differences in thefrequencies of oscillations. Aim 2 provides a more macro perspective on humanepisodic memory and navigation with a focus on the unique cortical-hippocampal andcortical-cortical networks that comprise spatial vs. temporal (order and interval)contextual processing. Building on experiments and a model we have developed overthe past funding period we will employ both whole brain fMRI and multilobular iEEGrecordings in patients undergoing seizure monitoring to determine the unique corticalcontributions to spatial vs. temporal context. We hypothesize that unique configurationsof networks and frequencies of interactions such as prefrontal-hippocampal interactionsfor temporal context and parietal-retrosplenial-hippocampal interactions for spatialcontext are critical to these representations. Proposed experiments directly test theseideas by again employing both episodic memory and navigation related paradigms. Theexpected outcomes from this proposal are a better understanding at both the micro andmacro level scale of how spatial vs. temporal context contribute to human episodicmemory and navigation. Specifically by better understanding the contributions of thehippocampal circuitry to episodic memory and navigation we can better understandhow diseases like stroke and ischemia impact function there. In addition by delineatingthe extra-hippocampal cortical contributions we can better understand and predictcompensation following insults to the hippocampus.