There is accumulating evidence that the entorhinal-hippocampal network is important for temporal memory. However, relatively little is known about the precise neurobiological mechanisms underlying memory for time. In particular, whether the lateral entorhinal cortex is involved in temporal processing remains an open question. During high-resolution fMRI scanning, participants watched a ~30-minute episode of a television show. During test, they viewed still-frames and indicated on a continuous timeline the precise time each still-frame was viewed during study. This procedure allowed us to measure error in seconds for each trial. We analyzed fMRI data from retrieval and found that high temporal precision was associated with increased BOLD fMRI activity in the anterolateral entorhinal (a homologue of the lateral entorhinal cortex in rodents) and perirhinal cortices, but not in the posteromedial entorhinal and parahippocampal cortices. This suggests a novel role for the lateral entorhinal cortex in processing of high-precision minute-scale temporal memories.

The medial temporal lobes play an important role in episodic memory, but over time, hippocampal contributions to retrieval may be diminished. However, it is unclear whether such changes are related to the ability to retrieve contextual information, and whether they are common across all medial temporal regions. Here, we used functional neuroimaging to compare neural responses during immediate and delayed recognition. Results showed that recollection-related activity in the posterior hippocampus declined after a 1-day delay. In contrast, activity was relatively stable in the anterior hippocampus and in neocortical areas. Multi-voxel pattern similarity analyses also revealed that anterior hippocampal patterns contained information about context during item recognition, and after a delay, context coding in this region was related to successful retention of context information. Together, these findings suggest that the anterior and posterior hippocampus have different contributions to memory over time and that neurobiological models of memory must account for these differences.DOI: http://dx.doi.org/10.7554/eLife.05025.001

Many scientists have become increasingly concerned with the course and status of science-related policies in recent years, and these concerns have only grown in the past months as governments have had to face a global pandemic. As experts in our respective fields, scientists have an obligation and an opportunity to help to inform science policy. We are a group of early-career scientists, four UC Irvine graduate students and one postdoc, who have seen great value in getting involved with political discourse and science policy. Each of us has been drawn to science policy for different reasons. For some, the decision to get involved has been deeply personal; Evelyn Valdez-Ward, for example, advocates for undocumented and marginalized scientists like herself. Some of us are concerned that, although we are only now beginning our research careers, our research could quite literally disappear with the onset of climate change if political action is not taken. Those of us who work in public health have seen the need to be engaged politically so that we can communicate with our communities, politicians, and funding agencies about how critical research is for our country's future health and safety. The current pandemic has likely altered the course of research in this Researchers eager to inform policy with science should seek out the pathways that are available for engaging with lawmakers at the state, local, or national level-while making sure to understand the nuances of political discourse.

The hippocampus plays a critical role in supporting episodic memory, in large part by binding together experiences and items with surrounding contextual information. At present, however, little is known about the roles of different hippocampal subfields in supporting this item–context binding. To address this question, we constructed a task in which items were affiliated with differing types of context—cognitive associations that vary at the local, item level and membership in temporally organized lists that linked items together at a global level. Participants made item recognition judgments while undergoing high-resolution fMRI. We performed voxel pattern similarity analyses to answer the question of how human hippocampal subfields represent retrieved information about cognitive states and the time at which a past event took place. As participants recollected previously presented items, activity patterns in the CA23DG subregion carried information about prior cognitive states associated with these items. We found no evidence to suggest reinstatement of information about temporal context at the level of list membership, but exploratory analyses revealed representations of temporal context at a coarse level in conjunction with representations of cognitive contexts. Results are consistent with characterizations of CA23DG as a critical site for binding together items and contexts in the service of memory retrieval.

The hippocampus plays a critical role in supporting episodic memory. 7Although we know that temporal context is a defining feature of episodic memory, we 8understand relatively little about how this information may be represented by the 9 hippocampus. Research in rodents has suggested that the hippocampus represents 10 temporal information on an absolute scale or in terms of relative temporal intervals, but 11 cognitive models of memory have argued that temporal context in episodic memory is a 12 consequence of changes in cognitive states and experiences. Here, we combined high-13resolution fMRI imaging with voxel pattern similarity analyses to answer the question of 14 how human hippocampal subfields represent retrieved information about cognitive 15 states and the time at which a past event took place. As participants recollected 16 previously presented items, activity patterns in the CA23DG subregion carried 17 information about prior cognitive states, along with coarse-grained information about 18 when the item was previously encountered. These findings are consistent with the idea 19

The medial temporal lobes play an important role in episodic memory, but over time, hippocampal contributions to retrieval may be diminished. However, it is unclear whether such changes are related to the ability to retrieve contextual information, and whether they are common across all medial temporal regions. Here, we used functional neuroimaging to compare neural responses during immediate and delayed recognition. Results showed that recollection-related activity in the posterior hippocampus declined after a 1-day delay. In contrast, activity was relatively stable in the anterior hippocampus and in neocortical areas. Multi-voxel pattern similarity analyses also revealed that anterior hippocampal patterns contained information about context during item recognition, and after a delay, context coding in this region was related to successful retention of context information. Together, these findings suggest that the anterior and posterior hippocampus have different contributions to memory over time and that neurobiological models of memory must account for these differences.

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