HIPPOCAMPUS ANATOMY SERIES
This observation was the basis of his lamellar hypothesis, which proposed that the hippocampus can be thought of as a series of parallel strips, operating in a functionally independent way. The perforant path-to-dentate gyrus-to-CA3-to-CA1 was called the trisynaptic circuit by Per Andersen, who noted that thin slices could be cut out of the hippocampus perpendicular to its long axis, in a way that preserves all of these connections. Subicular neurons send their axons mainly to the EC. Pyramidal cells of CA1 send their axons to the subiculum and deep layers of the EC. Pyramidal cells of CA3 send their axons to CA1. Granule cells of the DG send their axons (called "mossy fibers") to CA3. There is also a distinct pathway from layer 3 of the EC directly to CA1, often referred to as the temporoammonic or TA-CA1 pathway. These axons arise from layer 2 of the entorhinal cortex (EC), and terminate in the dentate gyrus and CA3. Most external input comes from the adjoining entorhinal cortex, via the axons of the so-called perforant path. The major signaling pathways flow through the hippocampus and combine to form a loop.
HIPPOCAMPUS ANATOMY PLUS
Most anatomists use the term "hippocampus proper" to refer to the four CA fields, and hippocampal formation to refer to the hippocampus proper plus dentate gyrus and subiculum. After this comes a pair of ill-defined areas called the presubiculum and parasubiculum, then a transition to the cortex proper (mostly the entorhinal area of the cortex). After CA1 comes an area called the subiculum. The CA areas are all filled with densely packed Pyramidal cells similar to those found in the neocortex. Next come a series of Cornu Ammonis areas: first CA4 (which underlies the dentate gyrus), then CA3, then a very small zone called CA2, then CA1. The first of these, the dentate gyrus (DG), is actually a separate structure, a tightly packed layer of small granule cells wrapped around the end of the hippocampus proper, forming a pointed wedge in some cross-sections, a semicircle in others. Starting at the dentate gyrus and working inward along the S-curve of the hippocampus means traversing a series of narrow zones. Basic hippocampal circuit Basic circuit of the hippocampus, shown using a modified drawing by Ramon y Cajal. While most neuroscientists no longer believe in the concept of a unified "limbic system", these regions are highly interconnected and do interact with one another. Paul MacLean once suggested, as part of his triune brain theory, that the limbic structures constitute the neural basis of emotion. These limbic structures include the hippocampus, cingulate cortex, olfactory cortex, and amygdala. The structures that line the edge of the hole collectively make up the so-called limbic system (Latin limbus = border), with the hippocampus lining the posterior edge of this hole. Topologically, the surface of a cerebral hemisphere can be regarded as a sphere with an indentation where it attaches to the midbrain. Shape of human hippocampus and associated structures. Neuroimaging pictures can show a number of different shapes, depending on the angle and location of the cut. Due to the three-dimensional curvature of this structure, two-dimensional sections such as shown are commonly seen. In primate brains, including humans, the portion of the hippocampus near the base of the temporal lobe is much broader than the part at the top. For example, in the rat, the two hippocampi look similar to a pair of bananas, joined at the stems.
HIPPOCAMPUS ANATOMY FULL
This general layout holds across the full range of mammalian species, from hedgehog to human, although the details vary. It has a distinctive, curved shape that has been likened to the sea-horse monster of Greek mythology and the ram's horns of Amun in Egyptian mythology. Hippocampus anatomy describes the physical aspects and properties of the hippocampus, a neural structure in the medial temporal lobe of the brain. Nissl-stained coronal section of the brain of a macaque monkey, showing hippocampus (circled). WikiMili Hippocampus anatomy Last updated JHuman hippocampus.
0 kommentar(er)
