What Is the Hippocampal Formation?

Hippocampal structure: The hippocampal structure is the part of the medial edge of the cerebral hemisphere cortex, belonging to the ancient cortex. This structure includes a part of the upper corpus callosum, bundle gyrus, dentate gyrus, hippocampus, lower leg, and hippocampal sulcus. Due to the extreme development of the neocortex, this cortex is pushed to the inner side of the hemisphere. It lies between the hippocampus and choroid, and bends downward with the development of the temporal lobe. It forms an arched gray matter area, but the development of each part is uneven.

Hippocampal structure: The hippocampal structure is the part of the medial edge of the cerebral hemisphere cortex, belonging to the ancient cortex. This structure includes a part of the upper corpus callosum, bundle gyrus, dentate gyrus, hippocampus, lower leg, and hippocampal sulcus. Due to the extreme development of the neocortex, this cortex is pushed to the inner side of the hemisphere. It lies between the hippocampus and choroid, and bends downward with the development of the temporal lobe. It forms an arched gray matter area, but the development of each part is uneven.

Chinese name

Hippocampal structure

Foreign name

hippocampus formation

The composition of the hippocampal structure:

The hippocampal structure includes complete structures and functional bodies including the hippocampus and its nearby dentate gyrus, bundle gyrus, upper corpus callosum, hippocampal hook and lower leg. It is closely related to the processing and motor functions of learning, memory, attention, emotion, sensory perception.

Morphological structure of hippocampal structure:

The hippocampal structure belongs to the cortex of the olfactory system. During the embryonic period, the coastal horse fissure is attached to the inner wall of the hemisphere, above the choroid fissure. With the formation of the temporal lobe, the hippocampal fissure and choroid fissure are squeezed down and forward. The arched hippocampal structure develops unevenly. Due to the invasion of the corpus callosum fibers, the part of the hippocampal structure above the corpus callosus rarely differentiates, forming a gray The lower part was not affected by the corpus callosum, and developed into the main part of the hippocampal structure, that is, the hippocampus that was trapped in the bottom of the lateral ventricle. The hippocampal structure is an important part of the limbic system, and it is also a high-profile area in modern epilepsy research. Some people think that the hippocampal structure is similar to an amplifier of epilepsy-like activity. A large number of experimental and clinical studies have found that hippocampal sclerosis, or medial temporal sclerosis, is closely related to temporal lobe seizures. In addition, the relationship between intractable epilepsy associated with low-grade malignant astrocytoma and loss of hippocampal neurons has been confirmed and confirmed by pathological studies. Although the causal relationship between epilepsy and hippocampal structural sclerosis is uncertain, it is generally believed that the two interact and affect each other. Hippocampal sclerosis is the basis of "epilepsy maturity". Different surgical methods designed by clinicians based on the structural characteristics of the hippocampus have achieved satisfactory results in controlling epilepsy.

The shape of the hippocampus structure:

The hippocampal structure is anterior and posterior, occupying the inner and lower parts of the temporal lobe, protruding from the medial side of the lateral ventricle at the base of the temporal angle of the lateral ventricle. The naming and differentiation of hippocampal structures has not yet been unified. It is usually divided from the outside to the inside (or from the bottom to the top) into the hippocampal gyrus, under the hippocampus, hippocampus, dentate gyrus (corner of hippocampus), chamber bed and hippocampus. The hippocampus is formed by several small cerebral gyruses that curl inwardly to cover the hippocampal sulcus. It is named after the appearance of the hippocampus, and the hippocampus seen when the temporal angle of the lateral ventricle is opened looks more like a silkworm or sheep's horn. The hippocampus is a hippocampus; the hippocampus is about 5cm long, and the hippocampus is slightly bent inward, connecting with the amygdaloid nucleus straddling the tip of the temporal angle of the lateral ventricle. The ventricular bed is a glittering white matter layer spreading on the ventricular surface of the hippocampus. This layer of white matter extends backward to form a hippocampal umbrella, which further extends inward and backward to form a dome.

1. Grey quilt:

The gray quilt is also called the upper corpus callosum. It is a thin layer of gray matter on the back of the corpus callosum. It enters the corpus callosum groove on both sides and migrates to the cingulate cortex at the bottom of the sulcus. It bypasses the corpus callosum forward and moves on both sides of the corpus callosum; it passes backwards around the corpus callosum and moves on both sides of the bundled gyrus. The bundle gyrus is a piece of gray matter that moves forward, downward, and outward in the dentate gyrus and hippocampus. On each side of the corpus callosum, there are two longitudinal fiber bundles. The one near the midline is called the medial longitudinal line, and the other one is called the lateral longitudinal line. The longitudinal fibers connect the lower corpus callosum forward and return to the hippocampal umbrella in a bundle. Carcass fibers may penetrate the corpus callosum and enter the fornix.

2. dentate gyrus:

The dentate gyrus is a narrow strip of gray matter, which is surrounded by the hippocampus except the inner side. The free surface of the dentate gyrus is separated by a horizontal groove to form a tooth shape. The back end is separated from the hippocampal umbrella and migrates in the bundle gyrus. Its front end reaches the notch of the hippocampal ditch, bends inward at an acute angle, and crosses the underside of the hippocampal ditch. This horizontal band is called the dentate tail. This horizontal band divides the hippocampal ditch into two parts, the front part is called ditch gyrus, and the rear part is called inner edge gyrus.

3. Hippocampus:

The hippocampus is a bow-shaped hump on the bottom of the lateral ventricle, with a wide front end and a shallow groove separated into 2 to 3 humps, which are claw-shaped, called the hippocampus. The rear end of the hippocampus migrates in the bundle gyrus. The surface of the hippocampus is covered with a ventricular membrane. The deep side of the membrane is a layer of white matter that becomes the ventricular bed. Its fibers gather toward the inner edge of the hippocampus, forming a longitudinal fiber bundle, called the hippocampus umbrella. The hippocampus moves backwards in the dome.

4. Settlement:

The lower cortex is the transitional cortex between the hippocampal cortex and the hippocampal cortex. From the six layers of the para hippocampal cortex to the three layers of the hippocampal cortex, the cortical area gradually changes from five layers to four layers, and the connections between different departments are also different . Therefore, the holder is often divided into four band-shaped areas: the side holder, the front holder, the holder and the cusp. Generally, the first two bands are classified as the entorhinal region, and the last two bands are classified as the hippocampus.

The function of hippocampal structure:

Anatomical and physiological studies have shown that the hippocampal structure is not related to the sense of smell, and the size of mammalian hippocampal shapes has not been directly related to the development of the sense of smell. Very well. In human brain samples lacking the olfactory bulb and olfactory tract, the hippocampus develops well. The hippocampus does not receive direct olfactory fibers from the olfactory bulb, but indirectly from the entorhinal area. Animal experiments show that when the hippocampus is removed, it does not affect the discrimination of the sense of smell, and the conditioned reflex function of the sense of smell still exists. Existing data indicate that hippocampus may be related to recent memory. When the hippocampus on both sides is damaged extensively, it can cause a high loss of recent memory, while long-term memory is usually not affected. The patient's loss of ability to learn new things and new technologies is consistent with the symptoms caused by bilateral mid-temporal resection. Some people believe that the hippocampus in the temporal lobe may work in conjunction with other neural structures during memory and recall. Clinical reports show that patients with severe "recent memory" disturbances after resection of the hippocampus including the hippocampus and the hippocampus in the hippocampus. The extent of the disorder usually depends on the extent of the hippocampal injury, but only when the frontal part of the temporal lobe is damaged, and Does not affect memory, memory impairment occurs only when the extent of the injury extends backwards into the hippocampus, dentate gyrus, and part of the hippocampus. The loss of memory usually occurs after damage to both the hippocampal structure and the hippocampal gyrus. Sometimes, some patients may have mild speech disturbance or memory impairment after partial resection of the temporal lobe of the dominant hemisphere. It is generally believed that the hippocampus on the opposite side of these cases must be damaged. In some patients with dementia with memory loss, the most obvious lesions can be found in the hippocampus. Research reports also indicate that the hippocampus is involved in emotional response or emotional control, participates in certain visceral activities, and has an effect on the ascending activation system of the brainstem reticular structure. [1]

Hippocampal structure and epilepsy:

The hippocampus has a very low seizure threshold. Originated from the episodic release of a part of the olfactory brain, it quickly spread to other areas of the olfactory brain and the lower part of the thalamus, or became diffuse. In the hippocampus and near the midline of the temporal lobe, structural sclerosis near the hippocampus is the most common pathological change in the brain of epilepsy patients at the time of autopsy. Therefore, it is considered that the temporal lobe is the most common cause of seizures in childhood. During hippocampal seizures, various psychomotor effects can occur, including olfactory, visual, tactile, and other types of hallucinations. Even if the patient loses consciousness, knowing that it is an illusion, it cannot be suppressed.