One of the most mysterious brain structures is the substantia nigra, or substantia nigra. Looking at its small size, we might be led to believe that it doesn’t play an important role. But we would be wrong. It is in fact a vital substance for our body.
In this article we will try to describe the substantia nigra and its functions, we will also show you which diseases can be associated with an alteration of the same.
Black substance, what is it?
It is a structure that is part of the basal ganglia, a circuit of interconnected nuclei. It is located in the midbrain area, but there is also evidence of it on both sides of the brain. This means that the substantia nigra is present in each of our cerebral hemisphere.
But why is it called that? The name is due to the dark color of the neurons that make up this structure and which is a consequence of neuromelanin, present in dopaminergic neurons, which are in turn present in large quantities in the substantia nigra.
The functions of the substantia nigra
The black substance is composed of two parts, each with its own functions that we describe below:
- Compact : in charge of the transmission of signals to the basal ganglia, but also of the initiation and regulation of the body’s motor capacity through the projection of dopaminergic neurons. This area of the substantia nigra is the darkest, as it contains the largest number of dopaminergic neurons.
- Reticulated : sends signals from the basal ganglia to different areas of the brain, especially the thalamus (one of the information control centers). Inside, this area contains a smaller amount of dopaminergic neurons.
To avoid misunderstandings, do not think that just because it is equipped with a smaller number of dopaminergic neurons, the cross-linked part does not play an equally essential role. This part is in fact responsible for neuronal inhibition through the neurotransmitter GABA.
The substantia nigra is associated with learning mechanisms, since it is responsible for mediating the brain response to stimuli. Its function is to facilitate learning thanks to the effects of dopamine. And it specializes in spatial learning.
Why this feature? When stimuli appear that we had not anticipated, a large amount of dopaminergic neurons are produced. Precisely this aspect makes the black substance the protagonist of learning, which as we have said several times contains a large number of these neurons. The substantia nigra does not manage learning alone, but uses the help of many other brain structures.
As mentioned at the beginning of the article, the substantia nigra is part of the basal ganglia, a set of nuclei that intervene in movement. With respect to this function, what exactly does the black substance do? Start and check the movements you need to activate our motor skills.
Eye movements affect the activation of exchanges between the reticulated part and the thalamus and other structures of our nervous system. These structures work together to stabilize the gaze, the movements of the face and the head. They also intervene in the visual phenomenon.
Reinforcement and reward
Dopaminergic neurons are also activated when we experience pleasant sensations. In fact, they intervene in the reward circuits. According to Bear, Connors and Paradiso, authors of the book Neuroscience. By exploring the brain , dark matter facilitates conducts that lead to gratification.
Consequently, even when we find ourselves repeating rewarding behavioral behaviors, we are acting thanks to the black substance. This is because we establish associations between stimuli and reactions. It is therefore linked to: motivation, reinforcements and addictions; since it can be triggered by the adaptive use of learning.
Another sphere in which we find the influence of dopaminergic neurons is that of sleep. Thanks to them, the biological rhythm of our sleep is regulated, in particular as regards wakefulness. We refer to the phase of sleep closest to awakening. In addition to this, they are related to the perception of time and the detection of stimulus intervals.
Diseases associated with substantia nigra
As we have seen, this brain structure acts on many motor functions of our organism. For this reason, its possible deficit can affect the development of various diseases. We list two of the most important:
- Schizophrenia. It is a disorder in which an alteration of the dopaminergic pathways occurs, as well as an increase in the levels of these neurotransmitters. It is therefore not uncommon for this disease to have symptoms associated with motivation and mood.
- Parkinson’s disease. Disease that involves a degeneration of dopaminergic neurons, in particular those present in the compact area of the substantia nigra. If we also reflect on the functions that the latter plays in the body, we can see how many of them are linked to the symptoms of this disease. We speak, for example, of motor alterations, mood and sleep.
In conclusion, the substantia nigra intervenes in movement, in motivation, in sleep, in the detection of stimulus intervals, in the mood, in learning and in the connection of nerve signals. An alteration could therefore cause serious problems to the mechanisms of which it is the protagonist.