What Is the Parahippocampal Gyrus?

Returning from the hippocampus:

Returning from the hippocampus:

The hippocampus is located on the medial side of the occipital lobe and the temporal lobe. As the main cortical input of the hippocampus, it has an important relationship with cognition and emotion. The hippocampus is an important center of emotional regulation and has always been an important nucleus for depression research. Para hippocampal gyrus-hippocampus-papillary body-prethalamic nucleus-cingulate gyrus-para hippocampal gyrus forms the hippocampal loop, which is related to emotion, learning and memory and other advanced neurological activities. The hippocampal gyrus is an important structure for the hippocampus to function, and its structural damage can cause abnormal emotions and cognitive behaviors. When a scholar studied the brain regions associated with depression and memory, he found that during learning tasks, the activity of para hippocampal gyrus increased, and the activity of prefrontal and parietal lobes decreased. In addition, some scholars performed a VBA analysis of gray matter and white matter in 21 patients with severe depression, and found that the gray matter volume in the hippocampal gyrus, hippocampus, middle frontal gyrus, and anterior cingulate gyrus decreased. These studies suggest that para hippocampus plays an important role in the neuropathology of depression.

Chinese name

Hippocampus

Foreign name

parahippocompalgyrus

Location

Medial below occipital lobe and temporal lobe

Front shape

Bend backwards

Anatomy of the hippocampus :

1. Hippocampus:

The hippocampus is a long, arched cortex formed by the anterior cortex of the temporal lobe being rolled into the ventral side. The coastal horse runs and is covered by the hippocampal gyrus. The functions of the hippocampus are: regulating food and drinking; related to memory; related to sexual behavior.

2. Occipital lobe:

The occipital lobe is relatively small and is the rear part of the hemisphere of the brain. It is divided into the dorsal lateral surface, medial lateral surface, and basal surface (cerebellopontine surface).

Dorsal lateral surface: The frontal boundary is not obvious. The line connecting the upper end of the parietal occipital groove to the anterior occipital notch can be used as the boundary with the parietal and temporal lobes. The sulcus of the occipital lobe is irregular, and the occipital transverse sulcus is common. It is a continuation of the interparietal sulcus downward and is approximately at right angles to it. There is a crescent-shaped groove in front of the occipital pole, and the rear end of the sulcus sometimes extends to the outer side of the back. The lateral occipital sulcus is a short, parallel sulcus that is slightly oblique to the dorsal medial edge and is sometimes divided into sections. The lateral occipital sulcus divides the occipital lobe into two parts: the part above the sulcus is called the upper occipital gyrus, and the part under the sulcus is called the lateral occipital gyrus.

Inner side: the wedge-shaped part between the posterior segment of the sulcus groove and the occipital sulcus is called wedge leaf; the part below the sulcus groove is lingual gyrus.

Bottom surface: The front boundary is not obvious, and the line connecting the notch from the front of the pillow to the lower part of the corpus callosum can be used as the front boundary. The sulcus gyrus on the underside is phase-shifted with the underside of the temporal lobe. The lingual gyrus is located between the talus sulcus and the lateral collateral, and the part between the lateral sulcus and the subtemporal sulcus is the posterior part of the fusiform gyrus.

Diseases related to hippocampus:

Hippocampal hook hernia (Cerebellum canopy hernia, canopy hiatus):

Any occupying lesion in the cerebral hemisphere on the celestial canopy can cause the ipsilateral hook gyrus and the lateral hippocampal gyrus to shift to the midline and sub-occipital direction and exit through the cerebellar celestial hiatus. This most often occurs when the occupying lesion is located in the temporal lobe. The width of the hernia is different depending on the volume of the canopy pool and the size of the occupying lesion. An anterior hernia is called an anterior hernia when it comes out of the hippocampus. This condition often occurs when the frontal lobe has a lesion. When the lesion occurs in the parietal occipital region, especially the occipital lesion, a posterior hernia of the hippocampus may occur, which is called a posterior hernia. When the entire hippocampus shows a semicircular hernia, it is called a total hippocampal hernia.

When a hippocampal hernia occurs, the midbrain narrows at the horizontal axis (left and right diameter) and the aqueduct is compressed. The contralateral cerebral foot is pushed to the contralateral free edge of the sky, and the ipsilateral oculomotor nerve is compressed between the edge of the sky and the posterior cerebral artery. Compression of the oculomotor nerve initially causes swelling, then bends at an angle on the posterior cerebral artery, and often causes bleeding within the nerve bundle. The resulting oculomotor nerve paralysis caused drooping eyelids, dilated pupils on the ipsilateral side, and the direct reflection of light disappeared, while the indirect opposite side of the light reflection disappeared. The upward and medial movements of the eyes disappeared, because the sixth cranial nerve lost its antagonism, and the eyeballs were deflected laterally under the action of other directions of movement. Mydriasis is the earliest symptom of a canopy hernia and can occur before conscious damage.

The dome hernia continues to expand, and wedge-shaped hemorrhagic necrosis will form at the edge of the sulcus formed by the coastal horse. Contralateral cerebral feet against the free edge of the sky can cause a hemorrhagic or non-bleeding infarction on the dorsal side of the brain. Any factor that can increase the pressure difference between the two sides of the cerebellum can aggravate the cerebellar canopy. Increased pressure differences can often cause rapid deterioration of neurological symptoms in patients, such as demining of the brain and loss of sensation. Obvious midline shift can cause interventricular foramen obstruction and narrowing of aqueduct to cause hydrocephalus and further increase ICP.

In addition to the consequences described above, increased ICP and cerebellar canopy hernia can also cause arterial compression, causing bleeding and infarction of brain tissue in different parts.