Formatio Reticularis: Structure, Function & Diseases

The formatio reticularis form a nerve plexus in the human brain that consists of gray as well as white matter (substantia alba and substantia grisea) and traverses the entire brainstem. It extends to the spinal cord and consists of extensive, diffusely connected neuron networks. The formatio reticularis controls, among other things, waking and sleeping states, the vital circulatory and respiratory centers, the vomiting center, and large parts of the motor system.

What is the formatio reticularis?

The formatio reticularis is a network of diverse neurons that extend from the brainstem to the spinal cord. The Latin term formatio reticularis is composed of the terms formatio (= shaping or formation) and reticulum (= small network). In German, the trivial name Hirnnetz (brain network) is also sometimes used. The term reticular formation is also commonly used. The neuronal network consists of white and gray matter (substantia alba and substantia grisea). The reticular formation processes information from all motor and sensory nuclei of the brain. It is home to the circulatory and respiratory centers and is involved in sleep and wakefulness control. Parts of the medical literature define the formatio reticularis negatively due to its strong interconnectedness. Accordingly, it includes all fiber tracts and neurons of the brainstem that do not clearly serve motor or sensory functions. However, the prerequisite should be that the fiber tracts or neurons are located in the mesencephalon, rhombencephalon, or myelencephalon (specific subregions of the brain). The advantage of this negative definition is that it eliminates the often difficult delineation of the individual subregions of the reticular formation.

Anatomy and structure

The formate reticularis can be divided into three major core groups. Accordingly, a distinction is made between

  • A median zone,
  • A lateral zone and
  • A laterally adjacent medial zone

distinguished. The median zone is composed of narrow cell plates called Raphne nuclei. This zone is used for information processing. Here, information from other areas of the brain (eg, the limbic system or the frontal cortex) is also received and transmitted. The lateral zone is mainly responsible for motor efferents. This zone is composed of small cells. In contrast, the laterally adjacent medial zone consists of comparatively large cells. From here, information and substances are transmitted to the thalamus and partially to the cortex (both are brain areas). In addition, information from the spinal cord, cerebellum, and sensory nerve nuclei of the brain arrives in the medial zones.

Function and tasks

The various zones of the formatio reticularis direct vital functions of the body. For example, vomiting and swallowing are controlled from here. The formatio reticularis are also involved in micturition. The term micturition is used to describe the physical process of emptying the urinary bladder. The special feature of the brain network is that it combines motor sub-functions into a holistic conduction (forwarding and bundling function). Here, information from almost all parts of the brain is brought together, processed and finally forwarded. A large part of the information is sent to the cerebellum, cerebrum and diencephalon. This is why we also speak of the brain network as the “bridge to the diencephalon”. The formatio reticularis also controls consciousness and the differentiation between waking and sleeping states. In the literature, it is also reported to be involved in pain control. Also involved is the formatio reticularis in controlling the circulatory system (cardiovascular system) as well as influencing the respiratory center. Because the brain network connects the limbic system to the nuclei of the hypothalamus, it also plays a role in the coloring of sensory input. In addition, it is involved in the formation and controls of human emotions.

Diseases

Post-traumatic stress disorder (PTSD or, according to the English, “post-traumatic stress disorder” PTSD) often occurs in connection with the formatio reticularis. The disorder results from events that are particularly traumatic and extremely difficult to process (e.g., wars, natural disasters, accidents, or rape).Medical literature estimates that 2-7% of people worldwide will be affected by PTSD once in their lifetime. The stress disorder restricts the everyday life of those affected and can become chronic if not treated properly. Timely therapy is therefore essential. The stress disorder always follows chronologically after a traumatic situation. However, it does not have to occur immediately afterwards. PTSD can also lead to noticeable symptoms many years after the trauma. These are intrusive, recurring memories of the traumatic event (called flashbacks). They can occur during sleep in the form of nightmares, but also during the day. Memory gaps are also possible. However, they are always characterized by great fear and a feeling of extreme helplessness. Those affected are therefore under massive tension. The connection between post-traumatic stress disorders and the formatio reticularis is explained in the literature by the fact that the stress disorders lead to permanent changes in the brain network. Such changes may also be the cause of sleep disorders because the formaio reticularis is significantly involved in the initiation of sleep or the control of waking and sleeping states. However, PTSD in particular has been treated exclusively psychologically or psychiatrically. Whether the therapy takes place on an inpatient or outpatient basis depends on the concrete manifestation in the individual case. This also determines whether or not drug treatment is necessary.