Striatum: Structure, Functions And Associated Disorders
The basal ganglia are fundamental structures for the regulation of movement and reward-motivated learning, among other functions. This part of the brain is made up of various nuclei, among which What we know as the “striatum” stands out
In this article we will describe the structure and functions of the striatum We will also explain its relationship with other brain regions and with certain physical and psychological disorders that occur as a result of alterations in the striatum.
The striatum It is also known as the “striate nucleus” and “neostriate.” It is a set of structures located at the subcortical level that is in turn part of the basal ganglia, involved in the regulation of intentional and automatic movements, as well as in procedural learning, reinforcement and planning.
The basal ganglia are located in the forebrain (or forebrain), below the lateral ventricles. They are formed by the caudate nucleus, the putamen, the nucleus accumbens, the olfactory tubercle, the globus pallidus, the substantia nigra and part of the subthalamus.
Technically, the term “striatum” encompasses most of the basal ganglia, with the exception of the substantia nigra and the subthalamic nucleus, since in the past these structures were conceived as a functionally related whole; However, thanks to recent research we have more information about the differences between these areas.
Nowadays we call the whole “striated” composed of the caudate nucleus, putamen and nucleus accumbens, which connects the two previous structures. For its part, the concept “striatum” is used above all to designate the combination of the striatum and the globus pallidus.
Structure and connections
The striatum is made up of two main sections: the dorsal and ventral striatum The first includes the putamen, the globus pallidus, and the caudate and lenticular nuclei, while the ventral striatum is made up of the nucleus accumbens and the olfactory bulb.
Most of the neurons that make up the striatum are medium spiny neurons, which owe their name to the shape of their dendrites. We can also find Deiter neurons, which have long dendrites with few branches, and interneurons, especially cholinergic and catecholaminergic.
The caudate and putamen, which together form the neostriatum, receive input from the cerebral cortex constituting the most important route through which information reaches the basal ganglia.
On the other hand, the output of the basal ganglia comes mainly from the globus pallidus, which, as we have said, is part of the striatum according to the classical definition, but not the striatum as such. GABAergic efferents are sent from the globus pallidus (and therefore inhibitory) indirectly to the premotor cortex, responsible for voluntary movement.
Functions of the striatum
Together, the basal ganglia carry out very varied functions, mainly related to motor skills. These nuclei contribute to the correct functioning of the following processes:
The striatum is related to most of these functions, constituting the most important part of the basal ganglia. Specifically, the ventral striatum mediates learning and motivated behavior through the secretion of dopamine, while the dorsal section is involved in movement control and executive functions.
Most disorders and diseases related to the striatum affect movements, both voluntary and automatic Parkinson’s disease and Huntington’s disease are two basic examples of basal ganglia dysfunction.
However, certain psychological alterations seem to be influenced by the functioning of this structure, mainly in relation to its role in the brain reward system.
1. Parkinson’s disease
Parkinson’s disease causes lesions in the brain, mainly in the basal ganglia. The death of dopaminergic neurons in the substantia nigra interferes with the release of dopamine in the striatum, causing motor symptoms such as slowness, rigidity, tremors and postural instability. Depressive symptoms also occur.
2. Huntington’s disease
During its initial phase, Huntington’s disease mainly affects the striatum; This explains why early symptoms are related to motor control, emotions and executive functions. In this case the basal ganglia are unable to inhibit unnecessary movements so hyperkinesia occurs.
3. Bipolar disorder
Research suggests that in some cases of bipolar disorder there are alterations in the genes that regulate the function of the striatum. Evidence in this regard has been found for both type I and type II bipolar disorder.
4. Obsessive-compulsive disorder and depression
Obsessive-compulsive disorder and depression, which They have a similar biological basis, have been associated with dysfunctions in the striatum. This would explain the decreased mood that occurs in both disorders; Difficulty inhibiting movements is also relevant in OCD.
5. Addictions
Dopamine is a neurotransmitter involved in the brain’s reward system; The pleasant sensations we feel when dopamine is released in the basal ganglia explain our motivation to again seek out the experiences we know are pleasurable. This explains addictions from a physiological point of view
