Theta-band phase locking during encoding leads to coordinated entorhinal-hippocampal replay

Precisely timed interactions between hippocampal and cortical neurons during replay epochs are thought to support learning. Indeed, research has shown that replay is associated with heightened hippocampal-cortical synchrony. Yet many caveats remain in our understanding. Namely, it remains unclear how this offline synchrony comes about, whether it is specific to particular behavioral states, and how-if at all-it relates to learning. In this study, we sought to address these questions by analyzing coordination between CA1 cells and neurons of the deep layers of the medial entorhinal cortex (dMEC) while rats learned a novel spatial task. During movement, we found a subset of dMEC cells that were particularly locked to hippocampal LFP theta-band oscillations and that were preferentially coordinated with hippocampal replay during offline periods. Further, dMEC synchrony with CA1 replay peaked ∼10 ms after replay initiation in CA1, suggesting that the distributed replay reflects extra-hippocampal information propagation and is specific to "offline" periods. Finally, theta-modulated dMEC cells showed a striking experience-dependent increase in synchronization with hippocampal replay trajectories, mirroring the animals' acquisition of the novel task and coupling to the hippocampal local field. Together, these findings provide strong support for the hypothesis that synergistic hippocampal-cortical replay supports learning and highlights phase locking to hippocampal theta oscillations as a potential mechanism by which such cross-structural synchrony comes about

Episodic memory development: Bridging animal and human research

Human episodic memory is not functionally evident until about 2 years of age and continues to develop into the school years. Behavioral studies have elucidated this developmental timeline and its constituent processes. In tandem, lesion and neurophysiological studies in non-human primates and rodents have identified key neural substrates and circuit mechanisms that may underlie episodic memory development. Despite this progress, collaborative efforts between psychologists and neuroscientists remain limited, hindering progress. Here, we seek to bridge human and non-human episodic memory development research by offering a comparative review of studies using humans, non-human primates, and rodents. We highlight critical theoretical and methodological issues that limit cross-fertilization and propose a common research framework, adaptable to different species, that may facilitate cross-species research endeavors

Coordinated grid and place cell replay during rest

Hippocampal replay has been hypothesized to underlie memory consolidation and navigational planning, yet the involvement of grid cells in replay is unknown. During replay we found grid cells to be spatially coherent with place cells, encoding locations 11 ms delayed relative to the hippocampus, with directionally modulated grid cells and forward replay exhibiting the greatest coherence with the CA1 area of the hippocampus. This suggests grid cells are engaged during the consolidation of spatial memories to the neocortex

Towards inclusive funding practices for early career researchers

Securing research funding is a challenge faced by most scientists in academic institutions worldwide. Funding success rates for all career stages are low, but the burden falls most heavily on early career researchers (ECRs). These are young investigators in training and new principal investigators who have a shorter track record. ECRs are dependent on funding to establish their academic careers. The low number of career development awards and the lack of sustained research funding result in the loss of ECR talent in academia. Several steps in the current funding process, from grant conditions to review, play significant roles in the distribution of funds. Furthermore, there is an imbalance where certain research disciplines and labs of influential researchers receive more funding. As a group of ECRs with global representation, we examined funding practices, barriers, and facilitators to the current funding systems. We also identified alternatives to the most common funding distribution practices, such as diversifying risk or awarding grants on a partly random basis. Here, we detail recommendations for funding agencies and grant reviewers to improve ECR funding prospects worldwide and promote a fairer and more inclusive funding landscape for ECRs.Instituto de VirologíaFil: de Winde, Charlotte M. University College London. MRC Laboratory for Molecular Cell Biology; Reino UnidoFil: de Winde, Charlotte M. Amsterdam University Medical Center. Department of Molecular Cell Biology & Immunology; Países BajosFil: Sarabipour, Sarvenaz. Johns Hopkins University. Department of Biomedical Engineering. Institute for Computational Medicine; Estados UnidosFil: Carignano, Hugo Adrian. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología e Innovaciones Tecnológicas; ArgentinaFil: Davla, Sejal. City University of New York. Advanced Science Research Center; Estados UnidosFil: Eccles, David. Malaghan Institute of Medical Research; Nueva ZelandaFil: Hainer, Sarah J. University of Pittsburgh. Department of Biological Sciences; Estados UnidosFil: Haidar, Mansour. Hasselt University; BélgicaFil: Ilangovan, Vinodh. Aarhus University; DinamarcaFil: Jadavji, Nafisa M. Midwestern University. Department of Biomedical Sciences; Estados UnidosFil: Jadavji, Nafisa M. Carleton University. Department of Neuroscience; CanadáFil: Kritsiligkou, Paraskevi. German Cancer Research Center; AlemaniaFil: Lee, Tai-Ying. University of Oxford; Reino UnidoFil: Ólafsdóttir, H. Freyja. Radboud University. Donders Institute for Brain, Cognition and Behaviour; Países Bajo

Efficient neural decoding of self-location with a deep recurrent network.

Place cells in the mammalian hippocampus signal self-location with sparse spatially stable firing fields. Based on observation of place cell activity it is possible to accurately decode an animal's location. The precision of this decoding sets a lower bound for the amount of information that the hippocampal population conveys about the location of the animal. In this work we use a novel recurrent neural network (RNN) decoder to infer the location of freely moving rats from single unit hippocampal recordings. RNNs are biologically plausible models of neural circuits that learn to incorporate relevant temporal context without the need to make complicated assumptions about the use of prior information to predict the current state. When decoding animal position from spike counts in 1D and 2D-environments, we show that the RNN consistently outperforms a standard Bayesian approach with either flat priors or with memory. In addition, we also conducted a set of sensitivity analysis on the RNN decoder to determine which neurons and sections of firing fields were the most influential. We found that the application of RNNs to neural data allowed flexible integration of temporal context, yielding improved accuracy relative to the more commonly used Bayesian approaches and opens new avenues for exploration of the neural code

Dissociation between dorsal and ventral posterior parietal cortical responses to incidental changes in natural scenes.

The posterior parietal cortex (PPC) is thought to interact with the medial temporal lobe (MTL) to support spatial cognition and topographical memory. While the response of medial temporal lobe regions to topographical stimuli has been intensively studied, much less research has focused on the role of PPC and its functional connectivity with the medial temporal lobe.Here we report a dissociation between dorsal and ventral regions of PPC in response to different types of change in natural scenes using an fMRI adaptation paradigm. During scanning subjects performed an incidental target detection task whilst viewing trial unique sequentially presented pairs of natural scenes, each containing a single prominent object. We observed a dissociation between the superior parietal gyrus and the angular gyrus, with the former showing greater sensitivity to spatial change, and the latter showing greater sensitivity to scene novelty. In addition, we observed that the parahippocampal cortex has increased functional connectivity with the angular gyrus, but not superior parietal gyrus, when subjects view change to the scene content.Our findings provide support for proposed dissociations between dorsal and ventral regions of PPC and suggest that the dorsal PPC may support the spatial coding of the visual environment even when this information is incidental to the task at hand. Further, through revealing the differential functional interactions of the SPG and AG with the MTL our results help advance our understanding of how the MTL and PPC cooperate to update representations of the world around us

Angular gyrus is functionally connected to the parahippocampal cortex during the viewing of novel scenes.

<p>PPI analyses, run on the scene novelty contrast, revealed that the right parahippocampal cortex had an enhanced connectivity with the left angular gyrus. The glass brain (<b>A</b>), along with Coronal and Axial sections for the left angular gyrus (<b>B</b>) at the peak levels for this contrast are displayed (<i>x,y,z</i> = −45, −58, 40; <i>t = </i>4.38). Threshold for these images is set at <i>p</i><0.001 (uncorrected for multiple comparisons). Activations are significant at <i>p</i><0.001 (uncorrected for multiple comparisons), cluster size >10 contiguous voxels. Peak coordinates are reported in Montreal Neurological Institute (MNI) space. L = Left side.</p

Experimental conditions were created by manipulating the second picture presented.

<p>These are illustrated here using one picture, a red inflatable boat on a lake. The position of the object (highlighted by the light grey ‘O’) and the background image (highlighted by the black ‘B’) were manipulated independently to create 5 conditions, these were: 1) there was no movement of any element of the picture (‘No_move’), 2) the background changed to a new position horizontally left or right of where it was previously located on the projection screen (‘Background_move’), 3) the object changed to a new position on the projection screen, moving horizontally left or right of where it was previously located (‘Object_move’), 4) the background and the object both changed to a new position, horizontally left or right of where they were previously located, with the each re-locating in the opposite direction (‘Object&background_move’), or 5) the whole scene (object and background) moves left or right (‘Scene_move’). Also included was a condition in which a completely new object and background was presented as the second picture (‘Novel_scene’). There was one further condition (not shown), the Repeat_scene condition, in which a previously seen scene was re-presented.</p

Eye-tracking analysis.

<p>The regions of interest (rectangular boxes) used for data analysis were: 1) the current object position, 2) the position of pre-stimulus fixation cross, and 3) the remainder of the scene (background). Fixations (overlaid circles), along with their durations, are shown. For this trial, three fixations were recorded on the current object region and accounted for 65.9% of the total viewing duration, the remaining fixation (34.1% of duration) occurred on the background. No fixations fell within the position of the pre-stimulus fixation cross.</p