Striated body: structure, functions and associated disorders
The basal ganglia are fundamental structures for the regulation of movement and for rewarding learning, among other functions. This part of the brain is composed of several nuclei, among which stand out those we know as “striated body” .
In this article we will describe the structure and functions of the striated body . We will also explain its relationship with other encephalic regions and with certain physical and psychological disorders that occur as a result of alterations in the striatum.
Striated body and basal ganglia
The striated body is also known as “striated nucleus” and “neo-striated” . It is a set of structures located at a subcortical level which in turn forms 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 is located in the prosencephalon (or anterior brain), below the lateral ventricles. They consist of the caudate nucleus, the putamen, the nucleus accumbens, the olfactory tuber, the globus pallidus, the substantia nigra and part of the subthalamus.
Technically the term “striated body” encompasses most of the basal ganglia, except for 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.
Today we call “striated” the set composed of the caudate nucleus, the putamen and the nucleus accumbens , which connects the two previous structures. The concept of “striated body” is used above all to designate the combination of the striated and the globus pallidus.
Structure and connections
The striated body is made up of two main sections: the dorsal and ventral striation . The former includes the putamen, the globus pallidus and the caudate and lenticular nuclei, while the ventral striatum is formed by the nucleus accumbens and the olfactory bulb.
Most of the neurons that make up the striatum are medium-sized spinal neurons, named after the shape of their dendrites. We can also find Deiter’s neurons, which have long dendrites with few branches, and interneurons, especially cholinergic and catecholaminergic ones.
The caudate and putamen, which together form the neostriatum receive afferences from the cerebral cortex , constituting the most important route by which information reaches the basal ganglia.
In contrast, the basal ganglia efferences start mainly from the globus pallidus, which, as we have said, is part of the striated body according to the classical definition, but not of the striation as such. From the globus pallidus, gabaergic (and therefore inhibitory) efferences are sent indirectly to the premotor cortex, which is responsible for voluntary movement.
Functions of the groove
As a whole, the basal ganglia carry out a variety of functions, mainly related to motor skills. These nuclei contribute to the correct functioning of the following processes:
- Motor learning.
- Processing of procedural memory.
- Beginning of the voluntary movements.
- Regulation of voluntary movements : direction, intensity, amplitude…
- Execution of automatic movements.
- Start of eye movements.
- Regulation of the working (or operational) memory.
- Focus of attention .
- Regulation of motivated behaviour (based on dopamine).
- Stock selection based on expected reward.
The striated body is related to most of these functions, as it constitutes the most important part of the basal ganglia. In particular, the ventral striatum mediates learning and motivated behaviour through dopamine secretion, while the dorsal section is involved in movement control and executive functions.
Most disorders and diseases related to the striated body 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’s 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 into the striatum, causing motor symptoms such as slowness, rigidity, tremors and postural instability. Symptoms of a depressive type also occur.
2. Huntington’s disease
During its initial phase, Huntington’s disease primarily affects the striatum; this explains why the 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 for this has been found for both type I and type II bipolar disorder.
4. Obsessive-compulsive disorder and depression
Obsessive-compulsive disorder and depression, which have a similar biological basis , have been associated with dysfunctions in the striatum. This would explain the decrease in mood that occurs in both disorders; in OCD, difficulty in inhibiting movement is also relevant.
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 go back to seeking the experiences we know are pleasurable. This explains addictions from a physiological point of view .