The putamen is a narrowing of the brain that is located right in the middle region of the brain. Together with the caudate nucleus it forms a subcortical region of the forebrain known as the striatum.
On the other hand, the putamen forms another important structure of the brain. Together with the globus pallidus it constitutes the extraventricular nucleus of the corpus striatum or lenticular nucleus.
Putamen (light blue)
Thus, the putamen is one of the three main nuclei of the basal ganglia of the brain, and at the same time, it forms two secondary structures through the union with two different nuclei.
At a functional level, it stands out for participating mainly in motor control of the body. Specifically, it seems to be especially involved in the execution of specific voluntary movements.
Characteristics of the putamen
The putamen is a brain structure that is located right in the center of the brain. The connection it establishes with the caudate nucleus constitutes the striatum, while its union with the globe pallidus gives rise to the lenticular nucleus.
Etymologically, the word putamen comes from Latin and refers to something that falls when pruning. Specifically, the term putamen comes from "putare" which means to prune.
It stands out for being one of the main nuclei of the basal ganglia of the brain. These ganglia form a group of gray matter masses that are located between the ascending and descending white matter pathways of the brain.
Thus, the putamen is a small region referring to the telencephalon, the most superior encephalic structure of the brain. This region is mainly responsible for motor control of the body, but recent research has linked it to other types of functions.
The functioning of the putamen together with the connection it establishes with other nuclei of the striatum could play an important role in processes such as learning or emotional regulation.
Putamen circuit
Putamen (orange color), Caudate nucleus (purple color)
The putamen circuit is a motor pathway that belongs to the basal ganglia. It determines a series of connections established by the putamen, which seem to play an especially important role in the execution of learned movements.
In fact, this circuit of the putamen is also known as a motor circuit, since it is the neural connection system that is responsible for motor programs according to the context.
However, this circuit does not start in the putamen, but in the cerebral cortex. Specifically, it has its beginning in the pre-motor, supplementary, primary motor, and somatosensory areas of the cerebral cortex.
These superior structures project glutamatergic nerve fibers to the putamen and, therefore, establish connection with said nucleus of the striatum. This projection of fibers is executed through two main channels: the direct route and the indirect route.
The direct pathway of the circuit ends in the internal globe pallidus and the reticular black substance. These structures project nerve fibers into the thalamus and return information to the cortex, thus forming a feedback loop.
In the indirect route, on the other hand, the putamen sends information to the external pale and this structure is responsible for projecting the fibers towards the subthalamic nucleus. Subsequently, the subthalamic nucleus projects into the medial pallidus and the reticular substantia nigra. Finally, the information is returned through the thalamus.
Functioning
Putamen (yellow)
The putamen is characterized by having a feedback activity with the cerebral cortex. That is, it collects information pertaining to these brain structures and, later, sends it back.
However, this connection is not made directly but projects the nerve fibers to other structures before they reach the motor cortex. In the same way, when the cerebral cortex projects towards the putamen, the information previously passes through other brain regions.
In this sense, through the direct route, the putamen connects with the cerebral cortex through the internal globe pallidus, the thalamus, and the reticular substantia nigra. In the indirect route, it does the same through the subthalamic nucleus, the internal pallidum and the reticular substantia nigra.
The two connecting paths operate in parallel and oppose each other. That is, the activation of the direct pathway reduces the inhibitory function of the internal pallidum and the reticular substantia nigra to the thalamus, which is disinhibited and sends more excitatory information to the cortex.
On the other hand, activation of the indirect pathway increases the activity of the subthalamic nucleus and, therefore, the inhibitory output of the internal pallidum and the reticular substantia nigra. In this case, the activity of the thalamus is decreased and less information is sent to the cortex.
Features
The putamen has three main functions: control of movement, reinforcement learning, and regulation of feelings of love and hate. While the first two activities are highly evidenced, the third is currently only a hypothesis.
With regard to movement, the putamen does not constitute a specialized structure for motor functions. However, its close relationship with other regions such as the caudate nucleus or accumbens, makes it participate in these types of activities.
On the other hand, many studies have shown that the putamen is a structure that plays an important role in different types of learning. The main ones are reinforcement learning and category learning.
Finally, a recent study carried out by the neurobiology laboratory at the University of London has postulated that the putamen participates in the regulation and development of feelings of love and hate.
Associated diseases
The putamen appears to be a brain structure involved in a large number of pathologies. Of all of them, the one most associated with its functioning is Parkinson's disease.
Likewise, other alterations such as cognitive impairment caused by Alzheimer's disease, Huntington's disease, Lewy body dementia, schizophrenia, depression, tourette syndrome or ADHD could also, in some cases, be associated with the functioning of this brain structure.
References
- Grillner, S; Ekeberg,; He, Manira; Lansner, A; Parker, D; Tegnér, J; Wallén, P (May 1998). "Intrinsic function of a neuronal network - a vertebrate central pattern generator". Brain research. Brain research reviews 26 (2-3): 184–97.
- Griffiths PD; Perry RH; Crossman AR (March 14, 1994). "A detailed anatomical analysis of neurotransmitter receptors in the putamen and caudate in Parkinson's disease and Alzheimer's disease." Neuroscience Letters. 169 (1–2): 68–72.
- Parent, André. »The History of the Basal Ganglia: The Contribution of Karl Friedrich Burdach». Neuroscience & Medicine. 03 (04): 374–379.
- Packard MG; Knowlton BJ (2002). "Learning and memory functions of the Basal Ganglia." Annu Rev Neurosci. 25 (1): 563–93.