Today, the structure is just called the hippocampus, with the term Cornu Ammonis (also known as Ammon's horn) surviving in the names of the hippocampal subfields CA1-CA4. The term hippocampus minor fell from use in anatomy textbooks and was officially removed in the Nomina Anatomica of 1895. In 1861 the hippocampus minor became the center of a dispute over human evolution between Thomas Henry Huxley and Richard Owen, satirized as the Great Hippocampus Question. Mayer mistakenly used the term hippopotamus in 1779, and was followed by some other authors until Karl Friedrich Burdach resolved this error in 1829. The renaming of the hippocampus as hippocampus major, and the calcar avis as hippocampus minor, has been attributed to Félix Vicq-d'Azyr systematizing nomenclature of parts of the brain in 1786. The hippocampus was then described as pes hippocampi major, with an adjacent bulge in the occipital horn, described as the pes hippocampi minor and later renamed as the calcar avis. Īnother reference appeared with the term pes hippocampi, which may date back to Diemerbroeck in 1672, introducing a comparison with the shape of the folded back forelimbs and webbed feet of the mythological hippocampus, a sea monster with a horse's forequarters and a fish's tail. This has survived in abbreviated form as CA in naming the subfields of the hippocampus. "Ram's horn" was proposed by the Danish anatomist Jacob Winsløw in 1732 and a decade later his fellow Parisian, the surgeon de Garengeot, used "cornu Ammonis" – horn of (the ancient Egyptian god) Amun, who was often represented as having a ram's head. The German anatomist Duvernoy (1729), the first to illustrate the structure, also wavered between "seahorse" and "silkworm". The earliest description of the ridge running along the floor of the temporal horn of the lateral ventricle comes from the Venetian anatomist Julius Caesar Aranzi (1587), who likened it first to a silkworm and then to a seahorse ( Latin hippocampus, from Greek ἱππόκαμπος, from Greek ἵππος, "horse" + κάμπος, "sea monster"). Image 1: The human hippocampus and fornix (left) compared with a seahorse (right) Hippocampal place cells interact extensively with head direction cells, whose activity acts as an inertial compass, and conjecturally with grid cells in the neighboring entorhinal cortex. Many neurons in the rat and mouse hippocampus respond as place cells: that is, they fire bursts of action potentials when the animal passes through a specific part of its environment. In rodents as model organisms, the hippocampus has been studied extensively as part of a brain system responsible for spatial memory and navigation. LTP is widely believed to be one of the main neural mechanisms by which memories are stored in the brain.
The form of neural plasticity known as long-term potentiation (LTP) was initially discovered to occur in the hippocampus and has often been studied in this structure. Since different neuronal cell types are neatly organized into layers in the hippocampus, it has frequently been used as a model system for studying neurophysiology. People with extensive, bilateral hippocampal damage may experience anterograde amnesia: the inability to form and retain new memories.
Damage to the hippocampus can also result from oxygen starvation ( hypoxia), encephalitis, or medial temporal lobe epilepsy. In Alzheimer's disease (and other forms of dementia), the hippocampus is one of the first regions of the brain to suffer damage short-term memory loss and disorientation are included among the early symptoms. In humans, it contains two main interlocking parts: the hippocampus proper (also called Ammon's horn), and the dentate gyrus. The hippocampus, as the medial pallium, is a structure found in all vertebrates. The hippocampus is located in the allocortex, with neural projections into the neocortex in humans, as well as primates. The hippocampus is part of the limbic system, and plays important roles in the consolidation of information from short-term memory to long-term memory, and in spatial memory that enables navigation. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus (via Latin from Greek ἱππόκαμπος, ' seahorse') is a major component of the brain of humans and other vertebrates.
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