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Published in Terence R. Anthoney, Neuroanatomy and the Neurologic Exam, 2017
On gross anatomical grounds, the hippocampus proper, the dentate gyrus, and the subiculum are contiguous and jointly make up the cortical structures buried within the hippocampal sulcus. By location, by larger size, and by relationship to the nearby alveus and fimbria, these structures are easily differentiable from other derivatives of the embryologic hippocampal formation, such as the indusium griseum. The hippocampus proper and the subiculum also have in common that they contribute efferent fibers to the fornix (e.g., C&S, p. 630; Nolt, p. 299). Indeed, Nauta and Feirtag state that “on that ground it [the ‘subiculum’] is a part of the hippocampus”—the “subiculum hippocampi” (1986, p. 275).
The Stress System
Published in Len Wisneski, The Scientific Basis of Integrative Health, 2017
In Chapter 1, we introduced you to the subiculum, a structure that runs along the length of the hippocampal formation. Not surprisingly, given its location, recent research indicates that the subiculum plays a role in memory, stress, and likely in the combination of the two experiences. In order to understand the significance of its role, we must first provide you with background information on this impressive little structure.
Transmitter Glutamate in Mammalian Hippocampus and Striatum
Published in Elling Kvamme, Glutamine and Glutamate in Mammals, 1988
The area dentata is the major entrance of fibers to the hippocampus. The perforant path, which originates in the enthorinal cortex, terminates in the outer molecular layer of the area dentata where it makes contact with the dendrites of the granular cells.4,5 The granular cells project their axons, the mossy fibers, to the pyramidal cells in hilus and in the CA3.6 The CA3 pyramidal cells project the so-called Schaffer collaterals with characteristic enpassage synapses to the CA1 pyramidal cell apical dendrites.7 The CA3 cells send a second branch of the axon through the fomix/fimbria mainly to the lateral septum.8 The CA1 pyramidal cells project further to the subiculum, but also send fibers through the fomix/fimbria. The pyramidal cells of the subiculum project to several brain regions such as the basal hypothalamus, nucleus accumbens, and mammillary bodies.8
Sectorization of the hippocampal formation: Cytoarchitectonics, topography, or vulnerability to hypoxia?
Published in Journal of the History of the Neurosciences, 2022
But the terminology related to these structures also shows some discrepancies: for example, the term hippocampal formation designates either the hippocampal complex to which is added the subiculum (Nieuwenhuys, Voogd, and van Huijzen 2008, 372) or all of these structures plus the entorhinal cortex (Standring 2016, 387). The Terminologia Anatomica, which is supposed to simplify the nomenclature and to clarify once and for all the meaning of terms used in morphological sciences, is unfortunately of very little help. It includes under the term “Hippocampus” the hippocampus proper (or Ammon’s horn, formed by regions I–IV or sectors CA1-C4), the subiculum and its subdivisions (why apart from the prosubiculum?), the fimbria, the layers of hippocampus, and the dentate gyrus with its layers (Federative Committee on Anatomical Terminology, 1998, 128).
Exploring the effect of chronotype on hippocampal volume and shape: A combined approach
Published in Chronobiology International, 2018
Charlotte Mary Horne, Ray Norbury
We did not observe an association between later chronotypes and global hippocampal volume. We did, however, observe more subtle localised atrophy related to chronotype in a mid-anterior region of the right hippocampus. Indeed, a number of studies in depressed patients have revealed localised shape changes in the absence of global reductions in volume. For example, Isikli et al. (2013) reported bilateral hippocampal shape alterations in currently depressed patients as compared to a matched group of healthy controls in a number of regions including an area on the inferior surface of the right hippocampus (subiculum) similar to that reported here. Similarly, Posener and colleagues, using high dimensional mapping of the hippocampus, reported inward deformations in the right subiculum of currently depressed patients (Posener et al. 2003). Bearden et al. (2009) observed that more severe symptom severity in unmedicated currently depressed patients was associated with greater left hippocampal atrophy in Cornu Ammonis (CA) 1 and subiculum (Bearden et al. 2009). More recently, Watanabe and colleagues (Watanabe et al. 2017) reported significant inward deformations in bilateral CA 1 and subiculum in first episode drug-naïve depressed patients as compared to a demographically similar healthy control group. In addition, within the patient group there was a linear relationship between the degree of deformation and serum cortisol levels.
Therapeutic potential of GABAA receptor subunit expression abnormalities in fragile X syndrome
Published in Expert Review of Precision Medicine and Drug Development, 2022
Mathijs B. van der Lei, R. Frank Kooy
There are some limitations regarding the detection of the expression of subunits of the GABAA receptor. The mRNA and protein expression of multiple subunits of the GABAA receptor is less well demarcated in the fragile X syndrome mouse model. For instance, the mRNA expression of the β1-3 subunits showed conflicting results with decreased or unaltered outcomes in the cortex and cerebellum of adult Fmr1 KO mice. Furthermore, the number of studies that investigated GABAA receptor expression is limited, resulting in the lack of data for several subunits in multiple brain regions at different ages. More studies are necessary to resolve these apparent discrepancies. Other limitations are the conflicting outcomes in reported mRNA and protein expression for the same subunit of the GABAA receptor, as for the δ subunit in the hippocampus in adult Fmr1 KO mice. mRNA is eventually translated into protein, but post transcriptional mechanisms and errors or noise in mRNA and protein experiments could for instance influence outcomes. Finally, the low overall abundancy for several subunits of the GABAA receptor could have prevented reliable detection of differential expression in other brain regions. For instance, the expression of the α5 subunit of the GABAA receptor was only decreased in the subiculum of adult Fmr1 KO mice, but unaltered in the hippocampus, cortex and cerebellum. Perhaps the overall low abundancy of the α5 subunit in the brain prevented reliable detection of differential expression in other brain regions than the subiculum. Of note, the α5 subunit is a potential interesting subunit, because it has been associated with learning and memory, and alterations in the expression of this subunit have been observed in patients with neurodevelopmental disorders including intellectual disability and autism [44].