Dopamine is one of the main neurotransmitters in the brain, best known for its involvement in pleasure-related processes and reward systems. However, its role in motor control is crucial, using the different dopaminergic pathways to cross the brain.
One of these neural networks is the black streak path. Throughout this article, we’ll talk about the structures that make it up, as well as its role in brain function and the clinical implications of its deterioration.
What is the black striped way?
The black streak path is one of the four pathways that make up the dopaminergic system. Along with the mesolimbic pathway, mesocortical pathway and tuberoinfundibular pathway, it is responsible for transporting dopamine from one place to another in the brain.
To be more precise, the black streak path is that the bundles are projected from the substantia nigra towards the corpus striatum, in particular towards the caudate nucleus and the putamen. This path plays a key role in engine control, Being the stimulation of intentional movement the main function of it.
Injuries or changes typical of disorders such as Parkinson’s disease or chorea affect the black streak path, causing many symptoms. D2 dopaminergic antagonists may also induce extrapyramidal symptoms associated with pseudoparkinsonism.
As mentioned above, the black streak path passes through the brain from the substantia nigra to the caudate nucleus and putamen, located in the corpus striatum.
1. Black substance
The substantia nigra is an area of the brain located in the midbrain, which stores dopamine-producing neurons. It is called a black substance because its tone is darker than other areas around it, due to the fact that his neuromelanin levels are the highest in the region.
The main function of dark matter is related to eye movements, motor control, reward-seeking, learning, and addiction. However, most of them are also mediated by the corpus striatum.
When this structure begins to disintegrate or begins a process of degeneration, conditions such as Parkinson’s disease appear, Which involves many motor and cognitive disorders.
2. Corpus striatum
Also called nucleus striata, the corpus striatum forms the subcortical part of the telencephalon. This structure is distinguished by being essential in the transmission of information to the basal ganglia.
The set of structures that make up the corpus striata are the caudate nucleus, putamen and nucleus accumbens. However, this article will only describe the former as being an essential part of the functioning of the black streak path.
3. Caudate nuclei
The structures called caudate nuclei are located approximately in the center of the brain, very close to the thalamus. We are talking about plural nuclei because there are two different nuclei inside each of the hemispheres of the brain.
Traditionally, the basal ganglia have been associated with higher order motor control. Within these functions, the caudate nucleus participates in the domain of voluntary control, as well as in the processes of learning and memory.
The putamen is a system also located in the central area of the brain, which plays an essential role in the control of movement, especially in the control and direction of fine voluntary movements.
In addition, the proper functioning of the putamen exerts a significant influence on the operating conditioning and recent studies qualify it as a source of feelings of love and hate.
Role in brain function
As we have seen, the black striated path, and the structures that compose it, are responsible for govern and promote the control of voluntary movements.
In general, movement control is the result of the successful combination of sensitive information and motor information coordinated by the central nervous system (CNS).
In this motor control we find voluntary and involuntary movements and reflexes. However, in this case, it is the voluntary movements that are controlled by the black streak path.
Voluntary movements are made with the intention of achieving a goal, that is, they are proactive. Outraged, most of these movements can be learned and improved by practice
Clinical implications and associated disorders
Knowing the structures related to the mesocortical pathway and the functions it performs, it will be much easier for us to understand what effects or consequences the decrease in activity in these neural networks implies.
This decrease in activity level can occur either by the administration of dopamine D2 antagonists, or by progressive degeneration of the pathway, which gives rise to diseases such as chorea or Parkinson’s disease.
D2 antagonists are commonly used in the treatment of stomach problems such as nausea, vomiting or gastrointestinal problems. However, its action as a dopamine antagonist can cause unwanted extrapyramidal effects such as dystonia or pseudoparkinsonian-like movements.
Choreas are a group of neurological conditions that are distinguished by causing a series of strange involuntary movements in the feet and hands in people. These impulses are caused by a series of intermittent and uneven muscle contractionsThat is, they do not have a repeating or rhythmic pattern, but seem to transmit from one muscle or another.
Within this group is the famous Huntington’s Korea, Benign Familial Chorea or Familial Reverse Choroatathesis.
Parkinson’s disease is a relatively common motor disorder in people over the age of 60. The origin of this disease lies in a decrease in the production of dopamine, in particular in the black streak path, which is no longer sufficient to meet the demands of the brain.
It is a disease that develops gradually, first affecting one side of the body and then acting on the other. The main symptoms of this disease are:
- Tremors in the upper and lower limbs, Hands, feet, jaw and face.
- Hardening of the muscles of the arms, legs and trunk.
- Slowness of movement.
- Balance alterations and coordination.