scholarly journals Complementary Roles of Hippocampus and Medial Entorhinal Cortex in Episodic Memory

2008 ◽  
Vol 2008 ◽  
pp. 1-8 ◽  
Author(s):  
P. A. Lipton ◽  
H. Eichenbaum
Keyword(s):  
Information Processing ◽  
Episodic Memory ◽  
Entorhinal Cortex ◽  
Spatial Information ◽  
Spatial Mapping ◽  
Hippocampal Function ◽  
Medial Entorhinal Cortex ◽  
Spatially Extended ◽  
Electrophysiological Findings ◽  
Hippocampal Networks

Spatial mapping and navigation are figured prominently in the extant literature that describes hippocampal function. The medial entorhinal cortex is likewise attracting increasing interest, insofar as evidence accumulates that this area also contributes to spatial information processing. Here, we discuss recent electrophysiological findings that offer an alternate view of hippocampal and medial entorhinal function. These findings suggest complementary contributions of the hippocampus and medial entorhinal cortex in support of episodic memory, wherein hippocampal networks encode sequences of events that compose temporally and spatially extended episodes, whereas medial entorhinal networks disambiguate overlapping episodes by binding sequential events into distinct memories.

scholarly journals Transient network synchrony of the developing medial entorhinal cortex

2017 ◽  
Author(s):  
Julia Dawitz ◽  
J.J. Johannes Hjorth ◽  
Tim Kroon ◽  
Marta Ruiperez-Alonso ◽  
Nandakumar Chandrasekhar ◽  
...  
Keyword(s):  
Entorhinal Cortex ◽  
Neuronal Networks ◽  
Gabaergic Inhibition ◽  
Medial Entorhinal Cortex ◽  
The Third ◽  
Tightly Coupled ◽  
Network Synchrony ◽  
Transient Network ◽  
Firing Properties ◽  
Hippocampal Networks

AbstractThe medial entorhinal cortex (MEC) contains a variety of specialized spatially-tuned neurons whose properties emerge during the third postnatal week onwards in rodents. How neuronal networks underlying the spatial firing patterns are formed is largely unknown but they are hypothesized to develop from topographic modules of synchronized neurons in superficial MEC. Here, we show that developing MEC neuronal networks in the second postnatal week are synchronously active in spatially-grouped modules. Network synchrony is intrinsic to MEC and desynchronized just prior to the emergence of spatially-tuned firing properties. The MEC network is modulated but not driven by the immature hippocampus and is tightly-coupled to neighboring neocortical networks. Unlike hippocampal networks, developing modules are dominated by glutamatergic excitation rather than GABAergic inhibition. Our results demonstrate that intrinsically synchronous modules exist in immature MEC: these may play a key role in establishing and organizing circuitry necessary for spatially-tuned firing properties of MEC neurons.

scholarly journals Homotopic Commissural Projections of Area Prostriata in Rat and Mouse: Comparison With Presubiculum and Parasubiculum

2020 ◽  
Vol 14 ◽  
Author(s):  
Chang-Hui Chen ◽  
Jin-Meng Hu ◽  
Sheng-Qiang Chen ◽  
Shi-Ming Liu ◽  
Song-Lin Ding
Keyword(s):  
Entorhinal Cortex ◽  
Visual Information ◽  
Rapid Detection ◽  
Spatial Information ◽  
Anatomical Structure ◽  
Medial Entorhinal Cortex ◽  
Connection Pattern ◽  
Projection Pattern ◽  
Tracing Techniques ◽  
Commissural Connections

Area prostriata in primates has recently been found to play important roles in rapid detection and processing of peripheral visual, especially fast-moving visual information. The prostriata in rodents was not discovered until recently and its connectivity is largely unknown. As a part of our efforts to reveal brain-wide connections of the prostriata in rat and mouse, this study focuses on its commissural projections in order to understand the mechanisms underlying interhemispheric integration of information, especially from peripheral visual field. Using anterograde, retrograde and Cre-dependent tracing techniques, we find a unique commissural connection pattern of the prostriata: its layers 2-3 in both hemispheres form strong homotopic commissural connections with few heterotopic projections to bilateral medial entorhinal cortex. This projection pattern is in sharp contrast to that of the presubiculum and parasubiculum, two neighbor regions of the prostriata. The latter two structures project very strongly to bilateral medial entorhinal cortex and to their contralateral counterparts. Our results also suggest the prostriata is a distinct anatomical structure from the presubiculum and parasubiculum and probably plays differential roles in interhemispheric integration and the balancing of spatial information between two hemispheres.

scholarly journals Egocentric coding of external items in the lateral entorhinal cortex

Science ◽  
2018 ◽  
Vol 362 (6417) ◽  
pp. 945-949 ◽  
Author(s):  
Cheng Wang ◽  
Xiaojing Chen ◽  
Heekyung Lee ◽  
Sachin S. Deshmukh ◽  
D. Yoganarasimha ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Spatial Cognition ◽  
Entorhinal Cortex ◽  
Essential Role ◽  
Reference Frames ◽  
Single Neurons ◽  
Spatial Coding ◽  
Medial Entorhinal Cortex ◽  
Neural Representations ◽  
Conscious Recollection

Episodic memory, the conscious recollection of past events, is typically experienced from a first-person (egocentric) perspective. The hippocampus plays an essential role in episodic memory and spatial cognition. Although the allocentric nature of hippocampal spatial coding is well understood, little is known about whether the hippocampus receives egocentric information about external items. We recorded in rats the activity of single neurons from the lateral entorhinal cortex (LEC) and medial entorhinal cortex (MEC), the two major inputs to the hippocampus. Many LEC neurons showed tuning for egocentric bearing of external items, whereas MEC cells tended to represent allocentric bearing. These results demonstrate a fundamental dissociation between the reference frames of LEC and MEC neural representations.

scholarly journals Medial entorhinal cortex activates in a traveling wave

2019 ◽  
Author(s):  
J.J. Hernández-Pérez ◽  
K.W. Cooper ◽  
E.L. Newman
Keyword(s):  
Information Processing ◽  
Entorhinal Cortex ◽  
Traveling Waves ◽  
Traveling Wave ◽  
Field Potential ◽  
Cortical Activity ◽  
Phase Shifts ◽  
Medial Entorhinal Cortex ◽  
Theta Phase ◽  
Cortical Information Processing

SummaryTraveling waves of cortical activity are hypothesized to organize cortical information processing and support interregional communication. Yet, it remains unknown whether interacting areas exhibit the matched traveling waves necessary to support this hypothesized form of interaction. Here, we show that the strongly-interacting medial entorhinal cortex (MEC) and hippocampus exhibit matched traveling waves. We demonstrate that both the field potential and spiking in the MEC exhibit prominent 6-12 Hz ‘theta’ traveling waves matching those of the hippocampus. The theta phase shifts observed along the MEC were accounted for largely by variation in waveform asymmetry. From this, we hypothesize that that gradients in local physiology underlie both the generation of MEC traveling waves and the functional variations observed previously across the MEC.

scholarly journals Object and object-memory representations across the proximodistal axis of CA1

2020 ◽  
Author(s):  
Brianna Vandrey ◽  
James A. Ainge
Keyword(s):  
Episodic Memory ◽  
Entorhinal Cortex ◽  
Place Cells ◽  
Spatial Representations ◽  
Place Field ◽  
Medial Entorhinal Cortex ◽  
Object Memory ◽  
Place Memory ◽  
Object Locations ◽  
Memory Representations

AbstractEpisodic memory requires information about objects to be integrated into a spatial framework. Place cells in the hippocampus encode spatial representations of objects that could be generated through signalling from the entorhinal cortex. Projections from lateral and medial entorhinal cortex to the hippocampus terminate in distal and proximal CA1, respectively. We recorded place cells in distal and proximal CA1 as rats explored an environment that contained objects. Place cells in distal CA1 demonstrated higher measures of spatial tuning and expressed place fields closer to objects. Further, remapping to object displacement was modulated by place field proximity to objects in distal, but not proximal CA1. Finally, representations of previous object locations were more precise in distal CA1. Our data suggest that lateral entorhinal cortex inputs to the hippocampus support spatial representations that are more precise and responsive to objects in cue-rich environments. This is consistent with functional segregation in the entorhinal-hippocampal circuits underlying object-place memory.

scholarly journals The role of the hippocampus in navigation is memory

2017 ◽  
Vol 117 (4) ◽  
pp. 1785-1796 ◽  
Author(s):  
Howard Eichenbaum
Keyword(s):  
Neural Activity ◽  
Spatial Navigation ◽  
Cognitive Maps ◽  
Spatial Mapping ◽  
Relational Memory ◽  
Hippocampal Function ◽  
Knowledge Domains ◽  
Considerable Research ◽  
Hippocampal Networks

There is considerable research on the neurobiological mechanisms within the hippocampal system that support spatial navigation. In this article I review the literature on navigational strategies in humans and animals, observations on hippocampal function in navigation, and studies of hippocampal neural activity in animals and humans performing different navigational tasks and tests of memory. Whereas the hippocampus is essential to spatial navigation via a cognitive map, its role derives from the relational organization and flexibility of cognitive maps and not from a selective role in the spatial domain. Correspondingly, hippocampal networks map multiple navigational strategies, as well as other spatial and nonspatial memories and knowledge domains that share an emphasis on relational organization. These observations suggest that the hippocampal system is not dedicated to spatial cognition and navigation, but organizes experiences in memory, for which spatial mapping and navigation are both a metaphor for and a prominent application of relational memory organization.

scholarly journals Mouse entorhinal cortex encodes a diverse repertoire of self-motion signals

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Caitlin S. Mallory ◽  
Kiah Hardcastle ◽  
Malcolm G. Campbell ◽  
Alexander Attinger ◽  
Isabel I. C. Low ◽  
...  
Keyword(s):  
Entorhinal Cortex ◽  
Medial Temporal Lobe ◽  
Visual Cues ◽  
Neural Circuits ◽  
Sensory Cues ◽  
Medial Entorhinal Cortex ◽  
Representation Of Space ◽  
Self Motion ◽  
Information Streams ◽  
Representations Of Space

AbstractNeural circuits generate representations of the external world from multiple information streams. The navigation system provides an exceptional lens through which we may gain insights about how such computations are implemented. Neural circuits in the medial temporal lobe construct a map-like representation of space that supports navigation. This computation integrates multiple sensory cues, and, in addition, is thought to require cues related to the individual’s movement through the environment. Here, we identify multiple self-motion signals, related to the position and velocity of the head and eyes, encoded by neurons in a key node of the navigation circuitry of mice, the medial entorhinal cortex (MEC). The representation of these signals is highly integrated with other cues in individual neurons. Such information could be used to compute the allocentric location of landmarks from visual cues and to generate internal representations of space.

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