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Menno P Witter - One of the best experts on this subject based on the ideXlab platform.
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development and topographical organization of projections from the hippocampus and parahippocampus to the retrosplenial cortex
European Journal of Neuroscience, 2019Co-Authors: Kamilla Gjerland Haugland, Jorgen Sugar, Menno P WitterAbstract:The rat hippocampal formation (HF), Parahippocampal Region (PHR), and retrosplenial cortex (RSC) play critical roles in spatial processing. These Regions are interconnected, and functionally dependent. The neuronal networks mediating this reciprocal dependency are largely unknown. Establishing the developmental timing of network formation will help to understand the emergence of this dependency. We questioned whether the long-range outputs from HF-PHR to RSC in Long Evans rats develop during the same time periods as previously reported for the intrinsic HF-PHR connectivity and the projections from RSC to HF-PHR. The results of a series of retrograde and anterograde tracing experiments in rats of different postnatal ages show that the postnatal projections from HF-PHR to RSC display low densities around birth, but develop during the first postnatal week, reaching adult-like densities around the time of eye-opening. Developing projections display a topographical organization similar to adult projections. We conclude that the long-range projections from HF-PHR to RSC develop in parallel with the intrinsic circuitry of HF-PHR and the projections of RSC to HF-PHR.
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postnatal development of retrosplenial projections to the Parahippocampal Region of the rat
eLife, 2016Co-Authors: Jorgen Sugar, Menno P WitterAbstract:Our ability to navigate critically depends on part of the brain called the Parahippocampal Region. Within this Region, there are several different types of brain cells (or neurons) whose activity “codes” different aspects of navigation, such as position, direction and speed. To understand how Parahippocampal neurons are able to form these activity patterns, we need to understand how they develop connections with neurons from other brain Regions that are important for navigation, such as the retrosplenial cortex. If inputs from retrosplenial neurons are important for generating the activity patterns observed in the Parahippocampal Region, the connections between the two groups of neurons should be fully mature before the activity patterns emerge. In rats, this should occur around 11–16 days after birth. Sugar and Witter have now assessed how the retrosplenial inputs are organized in the Parahippocampal Region of rats. This revealed that, when the rats are born, there are very few retrosplenial inputs present in the Parahippocampal Region. However, the few inputs that are present are organized similarly to how they eventually will be organized in adults. After birth, the number of inputs gradually increases until the rats are approximately 12 days old, at which point the pattern of connections is indistinguishable from what we observe in adults. Thus it appears that retrosplenial inputs are fully mature before activity patterns emerge in the Parahippocampal Region. In the future, Sugar and Witter would like to investigate how inputs to the Parahippocampal Region are able to organize themselves during early development. The importance of retrosplenial inputs could also be investigated by manipulating them during development and adulthood.
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a three plane architectonic atlas of the rat hippocampal Region
Hippocampus, 2015Co-Authors: Charlotte N Boccara, Lisa Jannicke Kjonigsen, Ingvild M Hammer, Jan G Bjaalie, Trygve B Leergaard, Menno P WitterAbstract:The hippocampal Region, comprising the hippocampal formation and the Parahippocampal Region, has been one of the most intensively studied parts of the brain for decades. Better understanding of its functional diversity and complexity has led to an increased demand for specificity in experimental procedures and manipulations. In view of the complex 3D structure of the hippocampal Region, precisely positioned experimental approaches require a fine-grained architectural description that is available and readable to experimentalists lacking detailed anatomical experience. In this paper, we provide the first cyto- and chemoarchitectural description of the hippocampal formation and Parahippocampal Region in the rat at high resolution and in the three standard sectional planes: coronal, horizontal and sagittal. The atlas uses a series of adjacent sections stained for neurons and for a number of chemical marker substances, particularly parvalbumin and calbindin. All the borders defined in one plane have been cross-checked against their counterparts in the other two planes. The entire dataset will be made available as a web-based interactive application through the Rodent Brain WorkBench (http://www.rbwb.org) which, together with this paper, provides a unique atlas resource.
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waxholm space atlas of the rat brain hippocampal Region three dimensional delineations based on magnetic resonance and diffusion tensor imaging
NeuroImage, 2015Co-Authors: Lisa Jannicke Kjonigsen, Jan G Bjaalie, Menno P Witter, Sveinung Lillehaug, Trygve B LeergaardAbstract:Abstract Atlases of the rat brain are widely used as reference for orientation, planning of experiments, and as tools for assigning location to experimental data. Improved quality and use of magnetic resonance imaging (MRI) and other tomographical imaging techniques in rats have allowed the development of new three-dimensional (3-D) volumetric brain atlas templates. The rat hippocampal Region is a commonly used model for basic research on memory and learning, and for preclinical investigations of brain disease. The Region features a complex anatomical organization with multiple subdivisions that can be identified on the basis of specific cytoarchitectonic or chemoarchitectonic criteria. We here investigate the extent to which it is possible to identify boundaries of divisions of the hippocampal Region on the basis of high-resolution MRI contrast. We present the boundaries of 13 divisions, identified and delineated based on multiple types of image contrast observed in the recently published Waxholm Space MRI/DTI template for the Sprague Dawley rat brain (Papp et al., Neuroimage 97:374–386, 2014). The new detailed delineations of the hippocampal formation and Parahippocampal Region (Waxholm Space atlas of the Sprague Dawley rat brain, v2.0) are shared via the INCF Software Center ( http://software.incf.org/ ), where also the MRI/DTI reference template is available. The present update of the Waxholm Space atlas of the rat brain is intended to facilitate interpretation, analysis, and integration of experimental data from this anatomically complex Region.
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topographic organization of orbitofrontal projections to the Parahippocampal Region in rats
The Journal of Comparative Neurology, 2014Co-Authors: Hideki Kondo, Menno P WitterAbstract:The Parahippocampal Region, which comprises the perirhinal, postrhinal, and entorhinal cortices, as well as the pre- and parasubiculum, receives inputs from several association cortices and provides the major cortical input to the hippocampus. This study examined the topographic organization of projections from the orbitofrontal cortex (OFC) to the Parahippocampal Region in rats by injecting anterograde tracers, biotinylated dextran amine (BDA) and Phaseolus vulgaris-leucoagglutinin (PHA-L), into four subdivisions of OFC. The rostral portion of the perirhinal cortex receives strong projections from the medial (MO), ventral (VO), and ventrolateral (VLO) orbitofrontal areas and the caudal portion of lateral orbitofrontal area (LO). These projections terminate in the dorsal bank and fundus of the rhinal sulcus. In contrast, the postrhinal cortex receives a strong projection specifically from VO. All four subdivisions of OFC give rise to projections to the dorsolateral parts of the lateral entorhinal cortex (LEC), preferentially distributing to more caudal levels of LEC. The medial entorhinal cortex (MEC) receives moderate input from VO and weak projections from MO, VLO, and LO. The presubiculum receives strong projections from caudal VO but only weak projections from other OFC Regions. As for the laminar distribution of projections, axons originating from OFC terminate more densely in upper layers (layers I-III) than in deep layers in the Parahippocampal Region. These results thus show a striking topographic organization of OFC-to-Parahippocampal connectivity. Whereas LO, VLO, VO, and MO interact with perirhinal-LEC circuits, the interactions with postrhinal cortex, presubiculum, and MEC are mediated predominantly through the projections of VO.
Asla Pitkanen - One of the best experts on this subject based on the ideXlab platform.
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projections from the periamygdaloid cortex to the amygdaloid complex the hippocampal formation and the Parahippocampal Region a pha l study in the rat
Hippocampus, 2003Co-Authors: Katarzyna Majak, Asla PitkanenAbstract:The periamygdaloid cortex, an amygdaloid Region that processes olfactory information, projects to the hippocampal formation and Parahippocampal Region. To elucidate the topographic details of these projections, pathways were anterogradely traced using Phaseolus vulgaris leukoagglutinin (PHA-L) in 14 rats. First, we investigated the intradivisional, interdivisional, and intra-amygdaloid connections of various subfields [periamygdaloid subfield (PAC), medial subfield (PACm), sulcal subfield (PACs)] of the periamygdaloid cortex. Thereafter, we focused on projections to the hippocampal formation (dentate gyrus, hippocampus proper, subiculum) and to the Parahippocampal Region (presubiculum, parasubiculum, entorhinal, and perirhinal and postrhinal cortices). The PACm had the heaviest intradivisional projections and it also originated light interdivisional projections to other periamygdaloid subfields. Projections from the other subfields converged in the PACs. All subfields provided substantial intra-amygdaloid projections to the medial and posterior cortical nuclei. In addition, the PAC subfield projected to the ventrolateral and medial divisions of the lateral nucleus. The heaviest periamygdalohippocampal projections originated in the PACm and PACs, which projected moderately to the temporal end of the stratum lacunosum moleculare of the CA1 subfield and to the molecular layer of the ventral subiculum. The PACm also projected moderately to the temporal CA3 subfield. The heaviest projections to the entorhinal cortex originated in the PACs and terminated in the amygdalo-entorhinal, ventral intermediate, and medial subfields. Area 35 of the perirhinal cortex was lightly innervated by the PAC subfield. Thus, these connections might allow for olfactory information entering the amygdala to become associated with signals from other sensory modalities that enter the amygdala via other nuclei. Further, the periamygdalohippocampal pathways might form one route by which the amygdala modulates memory formation and retrieval in the medial temporal lobe memory system. These pathways can also facilitate the spread of seizure activity from the amygdala to the hippocampal and Parahippocampal Regions in temporal lobe epilepsy. © 2003 Wiley-Liss, Inc.
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projections from the periamygdaloid cortex to the amygdaloid complex the hippocampal formation and the Parahippocampal Region a pha l study in the rat
Hippocampus, 2003Co-Authors: Katarzyna Majak, Asla PitkanenAbstract:The periamygdaloid cortex, an amygdaloid Region that processes olfactory information, projects to the hippocampal formation and Parahippocampal Region. To elucidate the topographic details of these projections, pathways were anterogradely traced using Phaseolus vulgaris leukoagglutinin (PHA-L) in 14 rats. First, we investigated the intradivisional, interdivisional, and intra-amygdaloid connections of various subfields [periamygdaloid subfield (PAC), medial subfield (PACm), sulcal subfield (PACs)] of the periamygdaloid cortex. Thereafter, we focused on projections to the hippocampal formation (dentate gyrus, hippocampus proper, subiculum) and to the Parahippocampal Region (presubiculum, parasubiculum, entorhinal, and perirhinal and postrhinal cortices). The PACm had the heaviest intradivisional projections and it also originated light interdivisional projections to other periamygdaloid subfields. Projections from the other subfields converged in the PACs. All subfields provided substantial intra-amygdaloid projections to the medial and posterior cortical nuclei. In addition, the PAC subfield projected to the ventrolateral and medial divisions of the lateral nucleus. The heaviest periamygdalohippocampal projections originated in the PACm and PACs, which projected moderately to the temporal end of the stratum lacunosum moleculare of the CA1 subfield and to the molecular layer of the ventral subiculum. The PACm also projected moderately to the temporal CA3 subfield. The heaviest projections to the entorhinal cortex originated in the PACs and terminated in the amygdalo-entorhinal, ventral intermediate, and medial subfields. Area 35 of the perirhinal cortex was lightly innervated by the PAC subfield. Thus, these connections might allow for olfactory information entering the amygdala to become associated with signals from other sensory modalities that enter the amygdala via other nuclei. Further, the periamygdalohippocampal pathways might form one route by which the amygdala modulates memory formation and retrieval in the medial temporal lobe memory system. These pathways can also facilitate the spread of seizure activity from the amygdala to the hippocampal and Parahippocampal Regions in temporal lobe epilepsy.
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projections from the posterior cortical nucleus of the amygdala to the hippocampal formation and Parahippocampal Region in rat
Hippocampus, 2002Co-Authors: Samuli Kemppainen, Esa Jolkkonen, Asla PitkanenAbstract:The posterior cortical nucleus of the amygdala is involved in the processing of pheromonal information and presumably participates in ingestive, defensive, and reproductive behaviors as a part of the vomeronasal amygdala. Recent studies suggest that the posterior cortical nucleus might also modulate memory processing via its connections to the medial temporal lobe memory system. To investigate the projections from the posterior cortical nucleus to the hippocampal formation and the Parahippocampal Region, as well as the intra-amygdaloid connectivity in detail, we injected the anterograde tracer phaseolus vulgaris-leucoagglutinin into different rostrocaudal levels of the posterior cortical nucleus. Within the hippocampal formation, the stratum lacunosum-moleculare of the temporal CA1 subfield and the adjacent molecular layer of the proximal temporal subiculum received a moderate projection. Within the Parahippocampal Region, the ventral intermediate, dorsal intermediate, and medial subfields of the entorhinal cortex received light to moderate projections. Most of the labeled terminals were in layers I, II, and III. In the ventral intermediate subfield, layers V and VI were also moderately innervated. Layers I and II of the parasubiculum received a light projection. There were no projections to the presubiculum or to the perirhinal and postrhinal cortices. The heaviest intranuclear projection was directed to the deep part of layer I and to layer II of the posterior cortical nucleus. There were moderate-to-heavy intra-amygdaloid projections terminating in the bed nucleus of the accessory olfactory tract, the central division of the medial nucleus, and the sulcal division of the periamygdaloid cortex. Our data suggest that via these topographically organized projections, pheromonal information processed within the posterior cortical nucleus can influence memory formation in the hippocampal and Parahippocampal areas. Also, these pathways provide routes through which seizure activity can spread from the epileptic amygdala to the surrounding Region of the temporal lobe. Hippocampus 2002;12:735–755. © 2002 Wiley-Liss, Inc.
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projections from the posterior cortical nucleus of the amygdala to the hippocampal formation and Parahippocampal Region in rat
Hippocampus, 2002Co-Authors: Samuli Kemppainen, Esa Jolkkonen, Asla PitkanenAbstract:The posterior cortical nucleus of the amygdala is involved in the processing of pheromonal information and presumably participates in ingestive, defensive, and reproductive behaviors as a part of the vomeronasal amygdala. Recent studies suggest that the posterior cortical nucleus might also modulate memory processing via its connections to the medial temporal lobe memory system. To investigate the projections from the posterior cortical nucleus to the hippocampal formation and the Parahippocampal Region, as well as the intra-amygdaloid connectivity in detail, we injected the anterograde tracer phaseolus vulgaris-leucoagglutinin into different rostrocaudal levels of the posterior cortical nucleus. Within the hippocampal formation, the stratum lacunosum-moleculare of the temporal CA1 subfield and the adjacent molecular layer of the proximal temporal subiculum received a moderate projection. Within the Parahippocampal Region, the ventral intermediate, dorsal intermediate, and medial subfields of the entorhinal cortex received light to moderate projections. Most of the labeled terminals were in layers I, II, and III. In the ventral intermediate subfield, layers V and VI were also moderately innervated. Layers I and II of the parasubiculum received a light projection. There were no projections to the presubiculum or to the perirhinal and postrhinal cortices. The heaviest intranuclear projection was directed to the deep part of layer I and to layer II of the posterior cortical nucleus. There were moderate-to-heavy intra-amygdaloid projections terminating in the bed nucleus of the accessory olfactory tract, the central division of the medial nucleus, and the sulcal division of the periamygdaloid cortex. Our data suggest that via these topographically organized projections, pheromonal information processed within the posterior cortical nucleus can influence memory formation in the hippocampal and Parahippocampal areas. Also, these pathways provide routes through which seizure activity can spread from the epileptic amygdala to the surrounding Region of the temporal lobe.
Howard Eichenbaum - One of the best experts on this subject based on the ideXlab platform.
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towards a functional organization of episodic memory in the medial temporal lobe
Neuroscience & Biobehavioral Reviews, 2012Co-Authors: Howard Eichenbaum, Norbert J. Fortin, Magdalena M Sauvage, Robert W Komorowski, Paul A LiptonAbstract:Here we describe a model of medial temporal lobe organization in which parallel “what” and “where” processing streams converge within the hippocampus to represent events in the spatio-temporal context in which they occurred; this circuitry also mediates the retrieval of context from event cues and vice versa, which are prototypes of episodic recall. Evidence from studies in animals are reviewed in support of this model, including experiments that distinguish characteristics of episodic recollection from familiarity, neuropsychological and recording studies that have identified a key role for the hippocampus in recollection and in associating events with the context in which they occurred, and distinct roles for Parahippocampal Region areas in separate “what” and “where” information processing that contributes to recollective and episodic memory.
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towards a functional organization of the medial temporal lobe memory system role of the Parahippocampal and medial entorhinal cortical areas
Hippocampus, 2008Co-Authors: Howard Eichenbaum, Paul A LiptonAbstract:The medial entorhinal cortex (MEC), home of the “grid cells” (Hafting et al., 2005), is a component of a large and complex system that connects widespread areas of the cerebral cortex with the hippocampus, known as the medial temporal lobe (MTL) system. It is generally agreed that this system supports declarative memory (Eichenbaum & Cohen, 2001; Squire et al., 2007). Notably, several investigators pursue the notion that components of this system support spatial information processing that underlies navigation, path integration, and cognitive mapping (e.g. McNaughton et al., 2006), and it is not clear whether these spatial processing functions are considered the same or distinct from the role of this system in memory (e.g., Leutgeb et al., 2005; Bird & Burgess, 2008). Many of the papers in this special issue focus on the role of the MEC and its grid cells in spatial processing. In contrast, here we consider the anatomical and functional organization of the entire MTL memory system, with particular attention paid to the MEC and neighboring parts of the Parahippocampal Region as components of that system. We first provide an overview of the anatomy of the system, wherein the inputs and outputs of the MEC and neighboring cortical areas will be highlighted. We then briefly review the literature on the functional roles of major components of the MTL system, contrasting functions of the hippocampus and the adjacent cortical areas including the MEC. Next we expand on the role of the MEC and its closest cortical associate, the Parahippocampal cortex, in humans and animals. At the conclusion of this review we suggest a role for the MEC that is quite different than the navigational function espoused by other papers in this special issue.
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evolution of declarative memory
Hippocampus, 2006Co-Authors: Joseph R. Manns, Howard EichenbaumAbstract:The present review considers research on the hippocampus and related areas from humans and experimental animals and makes three main points. First, many of the anatomical details of the hippocampus and adjacent cortical areas in the Parahippocampal Region are conserved across mammals. Second, the functional role of these areas in declarative memory is also conserved across species. Third, an evolutionary approach will be key to understanding exactly how the local circuitry of the hippocampus and Parahippocampal Region supports declarative memory. To highlight the utility of this approach, a schematic model is described in which separate streams of spatial and nonspatial information converge on the hippocampus. By this view, a fundamental function of the mammalian hippocampus is to combine incoming information about spatial context from the postrhinal (Parahippocampal in primates) cortex and medial entorhinal area with incoming information about nonspatial items from the perirhinal cortex and lateral entorhinal area. The underlying neurobiological computations that arise from local circuitry enable item-in-context memory and are proposed to be fundamental to many examples of declarative memory, including episodic memory in humans and spatial memory in experimental animals.
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a cortical hippocampal system for declarative memory
Nature Reviews Neuroscience, 2000Co-Authors: Howard EichenbaumAbstract:Recent neurobiological studies have begun to reveal the cognitive and neural coding mechanisms that underlie declarative memory--our ability to recollect everyday events and factual knowledge. These studies indicate that the critical circuitry involves bidirectional connections between the neocortex, the Parahippocampal Region and the hippocampus. Each of these areas makes a unique contribution to memory processing. Widespread high-order neocortical areas provide dedicated processors for perceptual, motor or cognitive information that is influenced by other components of the system. The Parahippocampal Region mediates convergence of this information and extends the persistence of neocortical memory representations. The hippocampus encodes the sequences of places and events that compose episodic memories, and links them together through their common elements. Here I describe how these mechanisms work together to create and re-create fully networked representations of previous experiences and knowledge about the world.
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memory representation within the Parahippocampal Region
The Journal of Neuroscience, 1997Co-Authors: Brian Young, Tim Otto, Gregory D Fox, Howard EichenbaumAbstract:The activity of 378 single neurons was recorded from areas of the Parahippocampal Region (PHR), including the perirhinal and lateral entorhinal cortex, as well as the subiculum, in rats performing an odor-guided delayed nonmatching-to-sample task. Nearly every neuron fired in association with some trial event, and every identifiable trial event or behavior was encoded by neuronal activity in the PHR. The greatest proportion of cells was active during odor sampling, and for many cells, activity during this period was odor selective. In addition, odor memory coding was reflected in two general ways. First, a substantial proportion of cells showed odor-selective activity throughout or at the end of the memory delay period. Second, odor-responsive cells showed odor-selective enhancement or suppression of activity during stimulus repetition in the recognition phase of the task. These data, combined with evidence that the PHR is critical for maintaining odor memories in animals performing the same task, indicate that this cortical Region mediates the encoding of specific memory cues, maintains stimulus representations, and supports specific match–nonmatch judgments critical to recognition memory. By contrast, hippocampal neurons do not demonstrate evoked or maintained stimulus-specific codings, and hippocampal damage results in little if any decrement in performance on this task. Thus it becomes increasingly clear that the Parahippocampal cortex can support recognition memory independent of the distinct memory functions of the hippocampus itself.
Rebecca D Burwell - One of the best experts on this subject based on the ideXlab platform.
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functional neuroanatomy of the Parahippocampal Region in the rat the perirhinal and postrhinal cortices
Hippocampus, 2007Co-Authors: Sharon C. Furtak, Kara L Agster, Rebecca D BurwellAbstract:The Parahippocampal Region in the rodent brain includes the perirhinal, postrhinal, and entorhinal cortices, the presubiculum, and the parasubiculum. In recent years, the perirhinal and postrhinal cortices have been a focus in memory research because they supply highly processed, polymodal sensory information to the hippocampus, both directly and via the entorhinal cortex. Available evidence indicates that these cortices receive different complements of cortical information, which are then forwarded to the hippocampus via parallel pathways.Here we have summarized the cortical, subcortical, and hippocampal connections of the perirhinal and postrhinal cortices in order to provide further insight into the nature of the information that is processed by these Regions prior to arriving in the hippocampus. As has been previously described, the cortical afferents of the rodent postrhinal cortex are dominated by structures known to be involved in the processing of visual and spatial information, whereas the cortical afferents of the perirhinal cortex result in remarkable convergence of polymodal sensory information. The two Regions are also differentiated by their cortical efferents. The perirhinal cortex projects more strongly to piriform, frontal, and insular Regions, whereas the postrhinal cortex projects preferentially to visual and visuospatial Regions. The subcortical connections of the two Regions provide further evidence that they have different functions. For example, the perirhinal cortex has strong reciprocal connections with the amygdala, which suggest involvement in processing affective stimuli. Subcortical input to the postrhinal cortex is dominated by projections from dorsal thalamic structures, particularly the lateral posterior nucleus. Although the perirhinal and postrhinal cortices are considered to contribute to the episodic memory system, many questions remain about their particular roles. A detailed description of the anatomical connections of the perirhinal and postrhinal cortices will permit the generation of new, anatomically guided, hypotheses about their role in episodic memory and other cognitive processes. © 2007 Wiley-Liss, Inc.
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functional neuroanatomy of the Parahippocampal Region in the rat the perirhinal and postrhinal cortices
Hippocampus, 2007Co-Authors: Sharon C. Furtak, Kara L Agster, Shauming Wei, Rebecca D BurwellAbstract:The Parahippocampal Region in the rodent brain includes the perirhinal, postrhinal, and entorhinal cortices, the presubiculum, and the parasubiculum. In recent years, the perirhinal and postrhinal cortices have been a focus in memory research because they supply highly processed, polymodal sensory information to the hippocampus, both directly and via the entorhinal cortex. Available evidence indicates that these cortices receive different complements of cortical information, which are then forwarded to the hippocampus via parallel pathways. Here we have summarized the cortical, subcortical, and hippocampal connections of the perirhinal and postrhinal cortices in order to provide further insight into the nature of the information that is processed by these Regions prior to arriving in the hippocampus. As has been previously described, the cortical afferents of the rodent postrhinal cortex are dominated by structures known to be involved in the processing of visual and spatial information, whereas the cortical afferents of the perirhinal cortex result in remarkable convergence of polymodal sensory information. The two Regions are also differentiated by their cortical efferents. The perirhinal cortex projects more strongly to piriform, frontal, and insular Regions, whereas the postrhinal cortex projects preferentially to visual and visuospatial Regions. The subcortical connections of the two Regions provide further evidence that they have different functions. For example, the perirhinal cortex has strong reciprocal connections with the amygdala, which suggest involvement in processing affective stimuli. Subcortical input to the postrhinal cortex is dominated by projections from dorsal thalamic structures, particularly the lateral posterior nucleus. Although the perirhinal and postrhinal cortices are considered to contribute to the episodic memory system, many questions remain about their particular roles. A detailed description of the anatomical connections of the perirhinal and postrhinal cortices will permit the generation of new, anatomically guided, hypotheses about their role in episodic memory and other cognitive processes.
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functional neuroanatomy of the Parahippocampal Region the lateral and medial entorhinal areas
Hippocampus, 2007Co-Authors: Kristin M Kerr, Kara L Agster, Sharon C. Furtak, Rebecca D BurwellAbstract:The entorhinal cortex (EC) serves a pivotal role in corticohippocampal interactions, but a complete description of its extrinsic connections has not been presented. Here, we have summarized the cortical, subcortical, and hippocampal connections of the lateral entorhinal area (LEA) and the medial entorhinal area (MEA) in the rat. We found that the targets and relative strengths of the entorhinal connections are strikingly different for the LEA and MEA. For example, the LEA receives considerably heavier input from the piriform and insular cortices, whereas the MEA is more heavily targeted by the visual, posterior parietal, and retrosplenial cortices. Regarding subcortical connections, the LEA receives heavy input from the amygdala and olfactory structures, whereas the MEA is targeted by the dorsal thalamus, primarily the midline nuclei and also the dorsolateral and dorsoanterior thalamic nuclei. Differences in the LEA and MEA connections with hippocampal and Parahippocampal structures are also described. In addition, because the EC is characterized by bands of intrinsic connectivity that span the LEA and MEA and project to different septotemporal levels of the dentate gyrus, special attention was paid to the efferents and afferents of those bands. Finally, we summarized the connections of the dorsocaudal MEA, the Region in which the entorhinal “grid cells” were discovered. The subRegional differences in entorhinal connectivity described here provide further evidence for functional diversity within the EC. It is hoped that these findings will inform future studies of the role of the EC in learning and memory. © 2007 Wiley-Liss, Inc.
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commentary functional neuroanatomy of the Parahippocampal Region the lateral and medial entorhinal areas
2007Co-Authors: Kristin M Kerr, Kara L Agster, Sharon C. Furtak, Rebecca D BurwellAbstract:The entorhinal cortex (EC) serves a pivotal role in corti- cohippocampal interactions, but a complete description of its extrinsic connections has not been presented. Here, we have summarized the cortical, subcortical, and hippocampal connections of the lateral ento- rhinal area (LEA) and the medial entorhinal area (MEA) in the rat. We found that the targets and relative strengths of the entorhinal connec- tions are strikingly different for the LEA and MEA. For example, the LEA receives considerably heavier input from the piriform and insular corti- ces, whereas the MEA is more heavily targeted by the visual, posterior parietal, and retrosplenial cortices. Regarding subcortical connections, the LEA receives heavy input from the amygdala and olfactory struc- tures, whereas the MEA is targeted by the dorsal thalamus, primarily the midline nuclei and also the dorsolateral and dorsoanterior thalamic nuclei. Differences in the LEA and MEA connections with hippocampal and Parahippocampal structures are also described. In addition, because the EC is characterized by bands of intrinsic connectivity that span the LEA and MEA and project to different septotemporal levels of the den- tate gyrus, special attention was paid to the efferents and afferents of those bands. Finally, we summarized the connections of the dorsocaudal MEA, the Region in which the entorhinal ''grid cells'' were discovered. The subRegional differences in entorhinal connectivity described here provide further evidence for functional diversity within the EC. It is hoped that these findings will inform future studies of the role of the EC in learning and memory. V C 2007 Wiley-Liss, Inc.
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The Parahippocampal Region: corticocortical connectivity.
Annals of the New York Academy of Sciences, 2006Co-Authors: Rebecca D BurwellAbstract:: The Parahippocampal Region, as defined in this review, comprises the cortical Regions that surround the rodent hippocampus including the perirhinal, postrhinal, and entorhinal cortices. The comparable Regions in the primate brain are the perirhinal, Parahippocampal, and entorhinal cortices. The perirhinal and postrhinal/Parahippocampal cortices provide the major polysensory input to the hippocampus through their entorhinal connections and are the recipients of differing combinations of sensory information. The differences in the perirhinal and postrhinal cortical afferentation have important functional implications, in part, because these two Regions project with different terminal patterns to the entorhinal cortex. The perirhinal cortex projects preferentially to the lateral entorhinal area (LEA), and the postrhinal cortex projects preferentially to the medial entorhinal area (MEA) and the caudal portion of LEA. Although the perirhinal and postrhinal cortices provide the major cortical input to the entorhinal cortex, the entorhinal cortex itself receives some direct cortical input. An examination of the cortical afferentation of the entorhinal cortex reveals an interesting principle of connectivity among these Regions; the composition of the direct neocortical input to the LEA is more similar to that of the perirhinal cortex, and the composition of the direct neocortical input to the MEA is more similar to that of the postrhinal cortex. Thus, polymodal associational input to the LEA and the MEA exhibits some segregation and is organized in parallel. The organization of intrinsic connections for each of the Parahippocampal Regions also contributes to the segregation of information into parallel pathways.
Marco De Curtis - One of the best experts on this subject based on the ideXlab platform.
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propagation dynamics of epileptiform activity acutely induced by bicuculline in the hippocampal Parahippocampal Region of the isolated guinea pig brain
Epilepsia, 2005Co-Authors: Laura Uva, Laura Librizzi, Fabrice Wendling, Marco De CurtisAbstract:Summary: Purpose: Aim of the study is to investigate the involvement of Parahippocampal subRegions in the generation and in the propagation of focal epileptiform discharges in an acute model of seizure generation in the temporal lobe induced by arterial application of bicuculline in the in vitro isolated guinea pig brain preparation. Methods: Electrophysiological recordings were simultaneously performed with single electrodes and multichannel silicon probes in the entorhinal, perirhinal, and piriform cortices and in the area CA1 of the hippocampus of the in vitro isolated guinea pig brain. Interictal and ictal epileptiform discharges restricted to the temporal Region were induced by a brief (3–5 min) arterial perfusion of the GABAA receptor antagonist, bicuculline methiodide (50 μM). Current source density analysis of laminar field profiles performed with the silicon probes was carried out at different sites to establish network interactions responsible for the generation of epileptiform potentials. Nonlinear regression analysis was conducted on extracellular recordings during ictal onset in order to quantify the degree of interaction between fast activities generated at different sites, as well as time delays. Results: Experiments were performed in 31 isolated guinea pig brains. Bicuculline-induced interictal and ictal epileptiform activities that showed variability of spatial propagation and time course in the olfactory–temporal Region. The most commonly observed pattern (n = 23) was characterized by the initial appearance of interictal spikes (ISs) in the piriform cortex (PC), which propagated to the lateral entorhinal Region. Independent and asynchronous preictal spikes originated in the entorhinal cortex (EC)/hippocampus and progressed into ictal fast discharges (around 25 Hz) restricted to the entorhinal/hippocampal Region. The local generation of fast activity was verified and confirmed both by CSD and phase shift analysis performed on laminar profiles. Fast activity was followed by synchronous afterdischarges that propagated to the perirhinal cortex (PRC) (but not to the PC). Within 1–9 min, the ictal discharge ceased and a postictal period of depression occurred, after which periodic ISs in the PC resumed. Unlike preictal ISs, postictal ISs propagated to the PRC. Conclusions: Several studies proposed that reciprocal connections between the entorhinal and the PRC are under a very efficient inhibitory control (1). We report that ISs determined by acute bicuculline treatment in the isolated guinea pig brain progress from the PC to the hippocampus/EC just before ictal onset. Ictal discharges are characterized by a peculiar pattern of fast activity that originates from the entorhinal/hippocampal Region and only secondarily propagates to the PRC. Postictal propagation of ISs to the PRC occured exclusively when an ictal discharge was generated in the hippocampal/entorhinal Region. The results suggest that reiteration of ictal events may promote changes in propagation pattern of epileptiform discharges that could act as trigger elements in the development of temporal lobe epilepsy.
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topographic distribution of direct and hippocampus mediated entorhinal cortex activity evoked by olfactory tract stimulation
European Journal of Neuroscience, 2004Co-Authors: Vadym Gnatkovsky, Laura Uva, Marco De CurtisAbstract:Olfactory information is central for memory-related functions, such as recognition and spatial orientation. To understand the role of olfaction in learning and memory, the distribution and propagation of olfactory tract-driven activity in the Parahippocampal Region needs to be characterized. We recently demonstrated that repetitive stimulation of the olfactory tract in the isolated guinea pig brain preparation induces an early direct activation of the rostrolateral entorhinal Region followed by a delayed response in the medial entorhinal cortex (EC), preceded by the interposed activation of the hippocampus. In the present study we performed a detailed topographic analysis of both the early and the delayed entorhinal responses induced by patterned stimulation of the lateral olfactory tract in the isolated guinea pig brain. Bi-dimensional maps of EC activity recorded at 128 recording sites with 4 x 4 matrix electrodes (410 microm interlead separation) sequentially placed in eight different positions, showed (i) an early (onset at 16.09 +/- 1.2 ms) low amplitude potential mediated by the monosynaptic LOT input, followed by (ii) an associative potential in the rostral EC which originates from the piriform cortex (onset at 33.2 +/- 2.3 ms), and (iii) a delayed potential dependent on the previous activation of the hippocampus. The sharp component of the delayed response had an onset latency between 52 and 63 ms and was followed by a slow wave. Laminar profile analysis demonstrated that in the caudomedial EC the delayed response was associated with two distinct current sinks located in deep and in superficial layers, whereas in the rostrolateral EC a small-amplitude sink could be detected in the superficial layers exclusively. The present report demonstrates that the output generated by the hippocampal activation is unevenly distributed across different EC subRegions and indicates that exclusively the medial and caudal divisions receive a deep-layer input from the hippocampus. In the rostrolateral EC, specific network interactions may be generated by the convergence of the direct olfactory input and the olfaction-driven hippocampal output.
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cytoarchitectonic characterization of the Parahippocampal Region of the guinea pig
The Journal of Comparative Neurology, 2004Co-Authors: Laura Uva, Marco De Curtis, Gerardo Biella, Sebastiaan Gruschke, Menno P WitterAbstract:The cytoarchitectonic features of the Parahippocampal Region (PHR) in the guinea pig are described, based on coronal, horizontal, and sagittal 50-μm sections stained for Nissl substance, zinc, parvalbumin, or calbindin. We differentiate between perirhinal (PRC), postrhinal (POR), and entorhinal (ERC) cortices. PRC is divided into areas 35 and 36 occupying the fundus and the dorsal bank of the rhinal fissure, respectively. POR is located caudal to the PRC. POR and area 36 show a dense, clustered cellular layer II and a thinner layer III in comparison to the adjacent neocortex, and they differ from each other with respect to the orientation of the somata of layer VI neurons. Area 35 is characterized by a thin layer II that is not very different from layer III. Layer IV is (dys)granular in area 36 and POR, and is absent in area 35 and ERC. ERC, located ventromedial to the PRC and POR, is subdivided in six fields, of which field 5 is adjacent to area 35. In both area 35 and field 5, no clear differentiation between layers II and III is present. Field 5 shows a darker cellular stain and exhibits a cell-free zone or lamina dissecans between layers III and V. Medial to field 5, an area characterized by large cell clusters in layer II is designated field 4. The latter field is replaced by field 3 rostromedially, which also typically shows clustering of layer II neurons. These cell clusters in field 3, however, are much more constant in size in spacing compared to those in field 4. The caudomedial portion of ERC is subdivided into fields 1, 1′, and 2. The latter, characterized by a homogeneous distribution of neurons in all layers with large darkly stained neurons in layer V is positioned rostral to field 1 and caudomedial to fields 4 and 5. In field 1, layers V and VI are thinner, and layer II neurons are smaller then in field 1′ and field 2. We conclude that the architectonic features of the guinea pig PHR are comparable to those described in other mammals, particularly the rat. J. Comp. Neurol. 474:289–303, 2004. © 2004 Wiley-Liss, Inc.
