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Current Biology : CB Jun 2023The mammalian entorhinal cortex routes inputs from diverse sources into the hippocampus. This information is mixed and expressed in the activity of many specialized...
The mammalian entorhinal cortex routes inputs from diverse sources into the hippocampus. This information is mixed and expressed in the activity of many specialized entorhinal cell types, which are considered indispensable for hippocampal function. However, functionally similar hippocampi exist even in non-mammals that lack an obvious entorhinal cortex or, generally, any layered cortex. To address this dilemma, we mapped extrinsic hippocampal connections in chickadees, whose hippocampi are used for remembering numerous food caches. We found a well-delineated structure in these birds that is topologically similar to the entorhinal cortex and interfaces between the hippocampus and other pallial regions. Recordings of this structure revealed entorhinal-like activity, including border and multi-field grid-like cells. These cells were localized to the subregion predicted by anatomical mapping to match the dorsomedial entorhinal cortex. Our findings uncover an anatomical and physiological equivalence of vastly different brains, suggesting a fundamental nature of entorhinal-like computations for hippocampal function.
Topics: Animals; Entorhinal Cortex; Hippocampus; Neurons; Brain; Songbirds; Mammals
PubMed: 37295426
DOI: 10.1016/j.cub.2023.05.031 -
Current Opinion in Neurobiology Oct 2021To plan trajectories and navigate, animals must maintain a mental representation of the environment and their own position within it. This "cognitive map" is thought to... (Review)
Review
To plan trajectories and navigate, animals must maintain a mental representation of the environment and their own position within it. This "cognitive map" is thought to be supported in part by the entorhinal cortex, where grid cells are active when an animal occupies the vertices of a scaling hierarchy of periodic lattices of locations in an enclosure. Here, we review computational developments which suggest that the grid cell network is: (a) efficient, providing required spatial resolution with a minimum number of neurons, (b) self-organizing, dynamically coordinating the structure and scale of the responses, and (c) adaptive, re-organizing in response to changes in landmarks and the structure of the boundaries of spaces. We consider these ideas in light of recent discoveries of similar structures in the mental representation of abstract spaces of shapes and smells, and in other brain areas, and highlight promising directions for future research.
Topics: Animals; Entorhinal Cortex; Models, Neurological; Neurons; Space Perception
PubMed: 34861597
DOI: 10.1016/j.conb.2021.11.007 -
Philosophical Transactions of the Royal... Jan 2023The neural coding of space centres on three foundational cell types: place cells, head direction cells and grid cells. One notable characteristic of these neurons is the... (Review)
Review
The neural coding of space centres on three foundational cell types: place cells, head direction cells and grid cells. One notable characteristic of these neurons is the symmetry properties of their spatial firing patterns. In symmetric environments, firing patterns are often also symmetric: for example, place cells show translational symmetry in aligned sub-compartments of a multi-compartment environment. A single head direction cell has a mirror-symmetric firing pattern, while a sub-class of head direction cells can show multi-fold rotational symmetries in multi-compartment environments, matching the symmetry of the recently experienced environment. The entorhinal grid cells are notable for the symmetry of their firing patterns in both rotational and translational domains. However, these symmetries are broken in a variety of situations. These symmetry-making and -breaking observations shed light on the underlying computations that generate these firing patterns, and also invite speculation as to whether they may have a functional role. This article outlines these findings and speculates on the consequences of the resultant firing symmetries and asymmetries for spatial coding and cognition. This article is part of a discussion meeting issue 'New approaches to 3D vision'.
Topics: Entorhinal Cortex; Space Perception; Neurons; Action Potentials
PubMed: 36511410
DOI: 10.1098/rstb.2021.0452 -
Scientific Reports Feb 2023Progesterone and its receptors (PRs) participate in mating and reproduction, but their role in spatial declarative memory is not understood. Male mice expressed PRs,...
Progesterone and its receptors (PRs) participate in mating and reproduction, but their role in spatial declarative memory is not understood. Male mice expressed PRs, predominately in excitatory neurons, in brain regions that support spatial memory, such as the hippocampus and entorhinal cortex (EC). Furthermore, segesterone, a specific PR agonist, activates neurons in both the EC and hippocampus. We assessed the contribution of PRs in promoting spatial and non-spatial cognitive learning in male mice by examining the performance of mice lacking this receptor (PRKO), in novel object recognition, object placement, Y-maze alternation, and Morris-Water Maze (MWM) tasks. In the recognition test, the PRKO mice preferred the familiar object over the novel object. A similar preference for the familiar object was also seen following the EC-specific deletion of PRs. PRKO mice were also unable to recognize the change in object position. We confirmed deficits in spatial memory of PRKO mice by testing them on the Y-maze forced alternation and MWM tasks; PR deletion affected animal's performance in both these tasks. In contrast to spatial tasks, PR removal did not alter the response to fear conditioning. These studies provide novel insights into the role of PRs in facilitating spatial, declarative memory in males, which may help with finding reproductive partners.
Topics: Animals; Male; Mice; Entorhinal Cortex; Hippocampus; Limbic System; Maze Learning; Memory Disorders; Progesterone; Receptors, Progesterone; Spatial Memory
PubMed: 36750584
DOI: 10.1038/s41598-023-29100-2 -
BMC Neuroscience Jun 2022To examine the pathological effect of a mesial temporal seizure onset zone (SOZ) on local and inter-regional response to faces in the amygdala and other structures of...
BACKGROUND
To examine the pathological effect of a mesial temporal seizure onset zone (SOZ) on local and inter-regional response to faces in the amygdala and other structures of the temporal lobe.
METHODS
Intracranial EEG data was obtained from the amygdala, hippocampus, fusiform gyrus and parahippocampal gyrus of nine patients with drug-refractory epilepsy during visual stimulation with faces and mosaics. We analyzed event-related potentials (ERP), gamma frequency power, phase-amplitude coupling and phase-slope-index and compared the results between patients with versus without a mesial temporal SOZ.
RESULTS
In the amygdala and fusiform gyrus, faces triggered higher ERP amplitudes compared to mosaics in both patient groups and higher gamma power in patients without a mesial temporal SOZ. In the hippocampus, famous faces triggered higher gamma power for both groups combined but did not affect ERPs in either group. The differentiated ERP response to famous faces in the parahippocampal gyrus was more pronounced in patients without a mesial temporal SOZ. Phase-amplitude coupling and phase-slope-index results yielded bidirectional modulation between amygdala and fusiform gyrus, and predominately unidirectional modulation between parahippocampal gyrus and hippocampus.
CONCLUSIONS
A mesial temporal SOZ was associated with an impaired response to faces in the amygdala, fusiform gyrus and parahippocampal gyrus in our patients. Compared to this, the response to faces in the hippocampus was impaired in patients with, as well as without, a mesial temporal SOZ. Our results support existing evidence for face processing deficits in patients with a mesial temporal SOZ and suggest the pathological effect of a mesial temporal SOZ on the amygdala to play a pivotal role in this matter in particular.
Topics: Electrocorticography; Epilepsy; Epilepsy, Temporal Lobe; Evoked Potentials; Hippocampus; Humans; Magnetic Resonance Imaging; Seizures
PubMed: 35698042
DOI: 10.1186/s12868-022-00715-x -
Nature Feb 2024The temporal lobe of the human brain contains the entorhinal cortex (EC). This region of the brain is a highly interconnected integrative hub for sensory and spatial... (Comparative Study)
Comparative Study
The temporal lobe of the human brain contains the entorhinal cortex (EC). This region of the brain is a highly interconnected integrative hub for sensory and spatial information; it also has a key role in episodic memory formation and is the main source of cortical hippocampal inputs. The human EC continues to develop during childhood, but neurogenesis and neuronal migration to the EC are widely considered to be complete by birth. Here we show that the human temporal lobe contains many young neurons migrating into the postnatal EC and adjacent regions, with a large tangential stream persisting until the age of around one year and radial dispersal continuing until around two to three years of age. By contrast, we found no equivalent postnatal migration in rhesus macaques (Macaca mulatta). Immunostaining and single-nucleus RNA sequencing of ganglionic eminence germinal zones, the EC stream and the postnatal EC revealed that most migrating cells in the EC stream are derived from the caudal ganglionic eminence and become LAMP5RELN inhibitory interneurons. These late-arriving interneurons could continue to shape the processing of sensory and spatial information well into postnatal life, when children are actively interacting with their environment. The EC is one of the first regions of the brain to be affected in Alzheimer's disease, and previous work has linked cognitive decline to the loss of LAMP5RELN cells. Our investigation reveals that many of these cells arrive in the EC through a major postnatal migratory stream in early childhood.
Topics: Animals; Child, Preschool; Humans; Infant; Cell Movement; Entorhinal Cortex; Ganglionic Eminence; Interneurons; Macaca mulatta; Neurons; Single-Cell Gene Expression Analysis; Temporal Lobe
PubMed: 38122823
DOI: 10.1038/s41586-023-06981-x -
PloS One 2022Impairment of cognitive functions is commonly observed in temporal lobe epilepsy (TLE). The aim of this study was to assess visuospatial memory functions and...
PURPOSE
Impairment of cognitive functions is commonly observed in temporal lobe epilepsy (TLE). The aim of this study was to assess visuospatial memory functions and memory-related networks using an adapted version of Roland's Hometown Walking (RHWT) functional MRI (fMRI) task in patients with TLE.
METHODS
We used fMRI to study activation patterns based on a visuospatial memory paradigm in 32 TLE patients (9 right; 23 left) and also within subgroups of lesional and non-lesional TLE. To test for performance, a correlational analysis of fMRI activation patterns and out-of-scanner neuropsychological visuospatial memory testing was performed. Additionally, we assessed memory-related networks using functional connectivity (FC).
RESULTS
Greater contralateral than ipsilateral mesiotemporal (parahippocampal gyrus/hippocampus) activation was observed in left (n = 23)/right (n = 9) TLE. In lesional left TLE (n = 17), significant activations were seen in right more than left mesiotemporal areas (parahippocampal gyrus), while non-lesional left TLE patients (n = 6) showed significant bilateral (left>right) activations in mesiotemporal structures (parahippocampal gyrus). In left TLE, visuospatial cognitive testing correlated with fMRI activations in left (parahippocampal gyrus) and right mesiotemporal structures (hippocampus), characterized by greater fMRI activation being associated with better memory scores. In right TLE, higher scores in visuospatial memory testing were associated with greater fMRI activations in left and right insular regions. FC patterns of memory-related networks differ in right and left TLE.
CONCLUSION
While TLE in general leads to asymmetrical mesiotemporal activation, lesion-induced and non-lesional TLE patients reveal different memory fMRI activation patterns. In right TLE, insular regions try to compensate for impaired right mesiotemporal structures during the performance of visuospatial tasks. Underlying functional visuospatial memory networks differ in right and left TLE.
Topics: Adolescent; Adult; Child; Cognition; Epilepsy, Temporal Lobe; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Space Perception; Spatial Memory; Visual Perception
PubMed: 35192676
DOI: 10.1371/journal.pone.0264349 -
Glia Aug 2022The entorhinal cortex-dentate gyrus circuit is centrally involved in memory processing conveying to the hippocampus spatial and nonspatial context information via,... (Review)
Review
The entorhinal cortex-dentate gyrus circuit is centrally involved in memory processing conveying to the hippocampus spatial and nonspatial context information via, respectively, medial and lateral perforant path (MPP and LPP) excitatory projections onto dentate granule cells (GCs). Here, we review work of several years from our group showing that astrocytes sense local synaptic transmission and exert in turn a presynaptic control at PP-GC synapses. Modulation of neurotransmitter release probability by astrocytes sets basal synaptic strength and dynamic range for long-term potentiation of PP-GC synapses. Intriguingly, this astrocyte control is circuit-specific, being present only at MPP-GC (not LPP-GC) synapses, which selectively express atypical presynaptic N-methyl-D-aspartate receptors (NMDAR) suitable to activation by astrocyte-released glutamate. Moreover, the astrocytic control is peculiarly dependent on the cytokine TNFα, which at constitutive levels acts as a gating factor for the astrocyte signaling. During inflammation/infection processes, increased levels of TNFα lead to uncontrolled astrocyte glutamate release, altered PP-GC circuit processing and, ultimately, impaired contextual memory performance. The TNFα-dependent pathological switch of the synaptic control from astrocytes and its deleterious consequences are observed in animal models of HIV brain infection and multiple sclerosis, conditions both known to cause cognitive disturbances in up to 50% of patients. The review also discusses open issues related to the identified astrocytic pathway: its role in contextual memory processing, potential damaging role in Alzheimer's disease, the existence of vesicular glutamate release from DG astrocytes, and the possible synaptic-like connectivity between astrocytic output sites and PP receptive sites.
Topics: Animals; Astrocytes; Cognition; Dentate Gyrus; Entorhinal Cortex; Glutamic Acid; Humans; Synapses; Tumor Necrosis Factor-alpha
PubMed: 34904753
DOI: 10.1002/glia.24128 -
Cognitive, Affective & Behavioral... Dec 2022Connectivity of the brain at rest can reflect individual differences and impact behavioral outcomes, including memory. The present study investigated how culture...
Connectivity of the brain at rest can reflect individual differences and impact behavioral outcomes, including memory. The present study investigated how culture influences functional connectivity with regions of the medial temporal lobe. In this study, 46 Americans and 59 East Asians completed a resting state scan after encoding pictures of objects. To investigate cross-cultural differences in resting state functional connectivity, left parahippocampal gyrus (anterior and posterior regions) and left hippocampus were selected as seed regions. These regions were selected, because they were previously implicated in a study of cultural differences during the successful encoding of detailed memories. Results revealed that left posterior parahippocampal gyrus had stronger connectivity with temporo-occipital regions for East Asians compared with Americans and stronger connectivity with parieto-occipital regions for Americans compared with East Asians. Left anterior parahippocampal gyrus had stronger connectivity with temporal regions for East Asians than Americans and stronger connectivity with frontal regions for Americans than East Asians. Although connectivity did not relate to memory performance, patterns did relate to cultural values. The degree of independent self-construal and subjective value of tradition were associated with functional connectivity involving left anterior parahippocampal gyrus. Findings are discussed in terms of potential cultural differences in memory consolidation or more general trait or state-based processes, such as holistic versus analytic processing.
Topics: Humans; Magnetic Resonance Imaging; Temporal Lobe; Brain Mapping; Brain; Hippocampus
PubMed: 35896854
DOI: 10.3758/s13415-022-01027-7 -
Hippocampus May 2023Hippocampal and parahippocampal gyrus spatial view neurons in primates respond to the spatial location being looked at. The representation is allocentric, in that the... (Review)
Review
Hippocampal and parahippocampal gyrus spatial view neurons in primates respond to the spatial location being looked at. The representation is allocentric, in that the responses are to locations "out there" in the world, and are relatively invariant with respect to retinal position, eye position, head direction, and the place where the individual is located. The underlying connectivity in humans is from ventromedial visual cortical regions to the parahippocampal scene area, leading to the theory that spatial view cells are formed by combinations of overlapping feature inputs self-organized based on their closeness in space. Thus, although spatial view cells represent "where" for episodic memory and navigation, they are formed by ventral visual stream feature inputs in the parahippocampal gyrus in what is the parahippocampal scene area. A second "where" driver of spatial view cells are parietal inputs, which it is proposed provide the idiothetic update for spatial view cells, used for memory recall and navigation when the spatial view details are obscured. Inferior temporal object "what" inputs and orbitofrontal cortex reward inputs connect to the human hippocampal system, and in macaques can be associated in the hippocampus with spatial view cell "where" representations to implement episodic memory. Hippocampal spatial view cells also provide a basis for navigation to a series of viewed landmarks, with the orbitofrontal cortex reward inputs to the hippocampus providing the goals for navigation, which can then be implemented by hippocampal connectivity in humans to parietal cortex regions involved in visuomotor actions in space. The presence of foveate vision and the highly developed temporal lobe for object and scene processing in primates including humans provide a basis for hippocampal spatial view cells to be key to understanding episodic memory in the primate and human hippocampus, and the roles of this system in primate including human navigation.
Topics: Animals; Humans; Primates; Hippocampus; Neurons; Parahippocampal Gyrus; Memory, Episodic; Spatial Navigation
PubMed: 36070199
DOI: 10.1002/hipo.23467