Diseases of the hippocampus
In some people suffering from depression, a decrease in the size (atrophy) of the hippocampus has been observed in studies. The people most affected were those with chronic depression (lasting for many years) or those with very early onset of the disease (in early adulthood). In the context of depression, there is a change in the concentration of the nerve messengers norepinephrine and serotonin.
As a result, the signal transmission between the nerve cells is weakened and nerve cells regress and shrink. At the same time, no further nerve cells are formed in the dentate gyrus (part of the hippocampus). These processes can be further intensified by a stress-induced release of the stress hormone cortisone during the development of depression.
For these reasons mentioned above, a shrinking of the hippocampus occurs in patients with chronic depression. With adequate drug therapy, the processes in the hippocampus are initially reversible.This topic could also be interesting for you: Medication for depressionThe hippocampus is the center for learning and memory processes in the brain. It transfers information from short-term to long-term memory.
For this reason, the hippocampus is one of the first structures in the brain affected by Alzheimer’s disease. While the exact causes for the development of Alzheimer’s disease are still unknown, it is considered certain that the deposition of protein degradation products (amyloid plaques, tau fibrils) leads to a disturbance in the signal transmission between nerve cells. The lack of signal transmission between the nerve cells leads to atrophy of the brain tissue.
These deposits of the above-mentioned protein degradation products can be detected in the hippocampus at an early stage of the disease. This disrupts important learning and memory processes. Especially the short-term memory is often affected at the beginning of the disease.
As the disease progresses, hippocampal atrophy (reduced growth of cells in the hippocampus with shrinking of brain tissue) can also occur. Sclerosis of the hippocampus, also known as hippocampal sclerosis, is accompanied by a large loss of nerve cells and is frequently associated with temporal lobe epilepsy. Sclerosis refers to a degenerative process that is accompanied by hardening.
Certain tissues or organs are transformed into functionless, sclerosed tissue. Among the clearly anatomically localizable forms of epilepsy, the temporal lobe epilepsy is the most severe variant in percentage terms. Typical symptoms are a preceding unpleasant feeling in the digestive tract, followed by repeated, brief loss of consciousness with rhythmic smacking movements of the mouth and spreading body movements.
In the majority of cases, the cause of epilepsy is a so-called mesial temporal sclerosis with varying degrees of nerve cell failure. One possible treatment option for sclerosis is surgical removal, in which the decreasing memory function is a side effect that must be calculated. An increasing sclerosis of the hippocampal region can also be observed in dementia.
In epilepsy, overexcitation of neurons in the brain occurs, which is manifested by numerous symptoms. The hippocampus is a frequent source of overexcitation in temporal lobe epilepsy. Long-term overexcitation of the nerve cells causes the nerve cells to die and the tissue to rebuild with increasing scarring in the area of the hippocampus (so-called ammonium horn sclerosis).
At the same time, the hippocampus also represents a target structure in the treatment of temporal lobe epilepsy with the help of deep brain stimulation. This therapeutic option is indicated in case of failure of drug therapy. In this case, a targeted stimulation of brain structures in the hippocampus with a low current intensity results in a decrease in the hyperexcitability of the nerve cells.
Hippocampal atrophy is a tissue loss due to a decrease in the number of cells in the hippocampus. This tissue loss can have numerous causes and can be detected by imaging (computed tomography, magnetic resonance imaging). Alzheimer’s disease is a common cause of atrophy of the hippocampus.
In this disease, a relevant atrophy of the brain tissue can be detected in early stages. Detection by imaging is an important component in the diagnosis of Alzheimer’s disease. Another cause of hippocampal atrophy is chronic depression.
However, visible atrophy of the tissue often only occurs in an advanced stage of depression. Especially the frequent influence of stress and psychological childhood traumas can significantly inhibit the growth of the hippocampus. In addition, a (silent) stroke can also lead to tissue loss in the hippocampus. The lack of blood supply to the nerve cells during a stroke leads to the death of these cells and subsequent scarring of the tissue.
