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Hippocampus Dec 2020High-level cognitive abilities such as navigation and spatial memory are thought to rely on the activity of grid cells in the medial entorhinal cortex (MEC), which...
High-level cognitive abilities such as navigation and spatial memory are thought to rely on the activity of grid cells in the medial entorhinal cortex (MEC), which encode the animal's position in space with periodic triangular patterns. Yet the neural mechanisms that underlie grid-cell activity are still unknown. Recent in vitro and in vivo experiments indicate that grid cells are embedded in highly structured recurrent networks. But how could recurrent connectivity become structured during development? And what is the functional role of these connections? With mathematical modeling and simulations, we show that recurrent circuits in the MEC could emerge under the supervision of weakly grid-tuned feedforward inputs. We demonstrate that a learned excitatory connectivity could amplify grid patterns when the feedforward sensory inputs are available and sustain attractor states when the sensory cues are lost. Finally, we propose a Fourier-based measure to quantify the spatial periodicity of grid patterns: the grid-tuning index.
Topics: Action Potentials; Animals; Entorhinal Cortex; Grid Cells; Humans; Models, Neurological; Neural Networks, Computer; Space Perception
PubMed: 33022854
DOI: 10.1002/hipo.23254 -
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 -
NeuroImage Feb 2020Neuroimaging has revealed numerous neural predictors of individual differences in creativity; however, with most of these identified in only one study, sometimes...
Neuroimaging has revealed numerous neural predictors of individual differences in creativity; however, with most of these identified in only one study, sometimes involving very small samples, their reliability is uncertain. To contribute to a convergent cognitive neuroscience of creativity, we conducted a pre-registered conceptual replication and extension study in which we assessed previously reported predictors of creativity using a multimodal approach, incorporating volumetric, white matter, and functional connectivity neuroimaging data. We assessed sets of pre-registered predictors against prevailing measures of creativity, including visual and verbal tests of divergent thinking, everyday creative behaviour, and creative achievement. We then conducted whole-brain exploratory analyses. Greater creativity was broadly predicted by features of the inferior frontal gyrus (IFG) and inferior parietal lobe (IPL), including both local grey matter and white matter predictors in the IFG, the superior longitudinal fasciculus that connects them, and IFG-IPL functional connectivity. As IFG and IPL are important nodes within executive control and default mode networks (DMN), respectively, this result supports the view that executive modulation of DMN activity optimizes creative ideation. Furthermore, white matter integrity of the basal ganglia was also a generalizable creativity predictor, and exploratory analyses revealed the anterior lobe of the cerebellum and the parahippocampal gyrus to both be reliable predictors of creativity across neuroimaging modalities. This pattern aligns with proposals ascribing roles of working and long-term memory to problem-solving and imagination. Overall, our findings help to consolidate some, but not all, neural correlates of individual differences that have been discussed in the cognitive neuroimaging of creativity, yielding a subset that appear particularly promising for focused future investigation.
Topics: Adult; Brain; Cerebellum; Connectome; Creativity; Gray Matter; Humans; Magnetic Resonance Imaging; Nerve Net; Parahippocampal Gyrus; Parietal Lobe; Prefrontal Cortex; White Matter
PubMed: 31654758
DOI: 10.1016/j.neuroimage.2019.116292 -
Annual Review of Vision Science Sep 2020The entorhinal cortex (EC) is a critical element of the hippocampal formation located within the medial temporal lobe (MTL) in primates. The EC has historically received... (Review)
Review
The entorhinal cortex (EC) is a critical element of the hippocampal formation located within the medial temporal lobe (MTL) in primates. The EC has historically received attention for being the primary mediator of cortical information going into and coming from the hippocampus proper. In this review, we highlight the significance of the EC as a major player in memory processing, along with other associated structures in the primate MTL. The complex, convergent topographies of cortical and subcortical input to the EC, combined with short-range intrinsic connectivity and the selective targeting of EC efferents to the hippocampus, provide evidence for subregional specialization and integration of information beyond what would be expected if this structure were a simple conduit of information for the hippocampus. Lesion studies of the EC provide evidence implicating this region as critical for memory and the flexible use of complex relational associations between experienced events. The physiology of this structure's constituent principal cells mirrors the complexity of its anatomy. EC neurons respond preferentially to aspects of memory-dependent paradigms including object, place, and time. EC neurons also show striking spatial representations as primates explore visual space, similar to those identified in rodents navigating physical space. In this review, we highlight the great strides that have been made toward furthering our understanding of the primate EC, and we identify paths forward for future experiments to provide additional insight into the role of this structure in learning and memory.
Topics: Animals; Entorhinal Cortex; Hippocampus; Memory; Neurons; Primates
PubMed: 32580662
DOI: 10.1146/annurev-vision-030320-041115 -
Current Biology : CB Sep 2023Hippocampal sharp-wave ripples (SPW-Rs) are critical for memory consolidation and retrieval. The neuronal content of spiking during SPW-Rs is believed to be under the...
Hippocampal sharp-wave ripples (SPW-Rs) are critical for memory consolidation and retrieval. The neuronal content of spiking during SPW-Rs is believed to be under the influence of neocortical inputs via the entorhinal cortex (EC). Optogenetic silencing of the medial EC (mEC) reduced the incidence of SPW-Rs with minor impacts on their magnitude or duration, similar to local CA1 silencing. The effect of mEC silencing on CA1 firing and field potentials was comparable to the effect of transient cortex-wide DOWN states of non-REM (NREM) sleep, implying that decreased SPW-R incidence in both cases is due to tonic disfacilitation of hippocampal circuits. The neuronal composition of CA1 pyramidal neurons during SPW-Rs was altered by mEC silencing but was restored immediately after silencing. We suggest that the mEC provides both tonic and transient influences on hippocampal network states by timing the occurrence of SPW-Rs and altering their neuronal content.
Topics: Entorhinal Cortex; Hippocampus; Neurons; Pyramidal Cells; Memory Consolidation; Action Potentials
PubMed: 37572665
DOI: 10.1016/j.cub.2023.07.039 -
Journal of Psychiatry & Neuroscience :... Jul 2020Childhood trauma is reliably associated with smaller hippocampal volume in adults; however, this finding has not been shown in children, and even less is known about how...
BACKGROUND
Childhood trauma is reliably associated with smaller hippocampal volume in adults; however, this finding has not been shown in children, and even less is known about how sex and trauma interact to affect limbic structural development in children.
METHODS
Typically developing children aged 9 to 15 years who completed a trauma history questionnaire and structural T1-weighted MRI were included in this study (n = 172; 85 female, 87 male). All children who reported 4 or more traumas (n = 36) composed the high trauma group, and all children who reported 3 or fewer traumas (n = 136) composed the low trauma group. Using multivariate analysis of covariance, we compared FreeSurfer-derived structural MRI volumes (normalized by total intracranial volume) of the amygdalar, hippocampal and parahippocampal regions by sex and trauma level, controlling for age and study site.
RESULTS
We found a significant sex × trauma interaction, such that girls with high trauma had greater volumes than boys with high trauma. Follow-up analyses indicated significantly increased volumes for girls and generally decreased volumes for boys, specifically in the hippocampal and parahippocampalregions for the high trauma group; we observed no sex differences in the low trauma group. We noted no interaction effect for the amygdalae.
LIMITATIONS
We assessed a community sample and did not include a clinical sample. We did not collect data about the ages at which children experienced trauma.
CONCLUSION
Results revealed that psychological trauma affects brain development differently in girls and boys. These findings need to be followed longitudinally to elucidate how structural differences progress and contribute to well-known sex disparities in psychopathology.
Topics: Adolescent; Adverse Childhood Experiences; Amygdala; Bereavement; Child; Exposure to Violence; Female; Hippocampus; Humans; Magnetic Resonance Imaging; Male; Organ Size; Parahippocampal Gyrus; Psychological Trauma; Sex Factors; Violence
PubMed: 32078279
DOI: 10.1503/jpn.190013 -
Cerebral Cortex (New York, N.Y. : 1991) Aug 2022Effective connectivity measurements in the human hippocampal memory system based on the resting-state blood oxygenation-level dependent signal were made in 172...
Effective connectivity measurements in the human hippocampal memory system based on the resting-state blood oxygenation-level dependent signal were made in 172 participants in the Human Connectome Project to reveal the directionality and strength of the connectivity. A ventral "what" hippocampal stream involves the temporal lobe cortex, perirhinal and parahippocampal TF cortex, and entorhinal cortex. A dorsal "where" hippocampal stream connects parietal cortex with posterior and retrosplenial cingulate cortex, and with parahippocampal TH cortex, which, in turn, project to the presubiculum, which connects to the hippocampus. A third stream involves the orbitofrontal and ventromedial-prefrontal cortex with effective connectivity with the hippocampal, entorhinal, and perirhinal cortex. There is generally stronger forward connectivity to the hippocampus than backward. Thus separate "what," "where," and "reward" streams can converge in the hippocampus, from which back projections return to the sources. However, unlike the simple dual stream hippocampal model, there is a third stream related to reward value; there is some cross-connectivity between these systems before the hippocampus is reached; and the hippocampus has some effective connectivity with earlier stages of processing than the entorhinal cortex and presubiculum. These findings complement diffusion tractography and provide a foundation for new concepts on the operation of the human hippocampal memory system.
Topics: Connectome; Entorhinal Cortex; Hippocampus; Humans; Parahippocampal Gyrus; Temporal Lobe
PubMed: 35034120
DOI: 10.1093/cercor/bhab442 -
Cortex; a Journal Devoted To the Study... Feb 2024Procrastination has adverse effects on personal growth and social development. Behavior research has found reward sensitivity is positively correlated with...
Procrastination has adverse effects on personal growth and social development. Behavior research has found reward sensitivity is positively correlated with procrastination. However, it remains unclear that the neural substrates underlie the relationship between reward sensitivity and procrastination. To address this issue, the present study used voxel-based morphometry (VBM) and resting-state functional connectivity (RSFC) analyses to investigate the neural substrates underlying the association with reward sensitivity and procrastination in two independent samples (N1 = 388, N2 = 330). In Sample 1, the behavioral result indicated reward sensitivity was positively correlated with procrastination. Moreover, the VBM analysis showed that reward sensitivity was positively associated with the gray matter volume (GMV) of the right parahippocampal gyrus. Furthermore, the RSFC result found reward sensitivity was negatively associated with the functional connectivity of the right parahippocampal gyrus-precuneus. Crucially, the mediation analysis revealed that functional connectivity of the right parahippocampal gyrus-precuneus mediated the relationship between reward sensitivity and procrastination. To verify the robustness of the results, confirmatory analysis was carried out in Sample 2. The results of Sample 1 (i.e., the behavioral, VBM, RSFC, and mediation results) can be verified in Sample 2. In brief, these findings suggested that the functional connectivity of the right parahippocampal gyrus-precuneus involved in reward impulsive control could modulate the relationship between reward sensitivity and procrastination, which is the first to reveal the neural underpinning of the association between reward sensitivity and procrastination.
Topics: Humans; Prefrontal Cortex; Brain Mapping; Procrastination; Magnetic Resonance Imaging; Parahippocampal Gyrus; Gray Matter; Parietal Lobe
PubMed: 38000138
DOI: 10.1016/j.cortex.2023.10.017 -
Nature Aug 2022Memory formation involves binding of contextual features into a unitary representation, whereas memory recall can occur using partial combinations of these contextual...
Memory formation involves binding of contextual features into a unitary representation, whereas memory recall can occur using partial combinations of these contextual features. The neural basis underlying the relationship between a contextual memory and its constituent features is not well understood; in particular, where features are represented in the brain and how they drive recall. Here, to gain insight into this question, we developed a behavioural task in which mice use features to recall an associated contextual memory. We performed longitudinal imaging in hippocampus as mice performed this task and identified robust representations of global context but not of individual features. To identify putative brain regions that provide feature inputs to hippocampus, we inhibited cortical afferents while imaging hippocampus during behaviour. We found that whereas inhibition of entorhinal cortex led to broad silencing of hippocampus, inhibition of prefrontal anterior cingulate led to a highly specific silencing of context neurons and deficits in feature-based recall. We next developed a preparation for simultaneous imaging of anterior cingulate and hippocampus during behaviour, which revealed robust population-level representation of features in anterior cingulate, that lag hippocampus context representations during training but dynamically reorganize to lead and target recruitment of context ensembles in hippocampus during recall. Together, we provide the first mechanistic insights into where contextual features are represented in the brain, how they emerge, and how they access long-range episodic representations to drive memory recall.
Topics: Animals; Brain Mapping; Entorhinal Cortex; Gyrus Cinguli; Hippocampus; Longitudinal Studies; Mental Recall; Mice; Models, Neurological; Neural Inhibition
PubMed: 35831504
DOI: 10.1038/s41586-022-04936-2 -
Hippocampus Dec 2019In this review, we aim to reappraise the organization of intrinsic and extrinsic networks of the entorhinal cortex with a focus on the concept of parallel cortical... (Review)
Review
In this review, we aim to reappraise the organization of intrinsic and extrinsic networks of the entorhinal cortex with a focus on the concept of parallel cortical connectivity streams. The concept of two entorhinal areas, the lateral and medial entorhinal cortex, belonging to two parallel input-output streams mediating the encoding and storage of respectively what and where information hinges on the claim that a major component of their cortical connections is with the perirhinal cortex and postrhinal or parahippocampal cortex in, respectively, rodents or primates. In this scenario, the lateral entorhinal cortex and the perirhinal cortex are connectionally associated and likewise the postrhinal/parahippocampal cortex and the medial entorhinal cortex are partners. In contrast, here we argue that the connectivity matrix emphasizes the potential of substantial integration of cortical information through interactions between the two entorhinal subdivisions and between the perirhinal and postrhinal/parahippocampal cortices, but most importantly through a new observation that the postrhinal/parahippocampal cortex projects to both lateral and medial entorhinal cortex. We suggest that entorhinal inputs provide the hippocampus with high-order complex representations of the external environment, its stability, as well as apparent changes either as an inherent feature of a biological environment or as the result of navigating the environment. This thus indicates that the current connectional model of the parahippocampal region as part of the medial temporal lobe memory system needs to be revised.
Topics: Animals; Entorhinal Cortex; Humans; Nerve Net; Neural Pathways; Neurons
PubMed: 31408260
DOI: 10.1002/hipo.23145