Putamen: structure, functions, and related disorders

The basal ganglia are a subcortical region that is involved in various physical and cognitive functions, particularly in movement, both voluntary and automatic. The nuclei that make up this superstructure have been grouped in different ways, giving rise to names that overlap with each other.

The putamen is one of the sections of the basal ganglia. In this article we will describe the structure, functions, and disorders associated with injury to the putamen, paying special attention to the relationship of this nucleus with the rest of the regions of the ganglia basal.

• Related article: "Basal ganglia: anatomy and functions"

What is the putamen?

The putamen is a brain structure that plays a fundamental role in the preparation and execution of limb movements. It is part of the anatomical-functional region known as the “basal ganglia”, which regulates voluntary motor skills, automatic habits and procedural learning.

It is formed by Gray matter, that is, by bodies of neurons, unmyelinated dendrites and glial cells. It is located below the cerebral hemispheres, at the base of the telencephalon and in the central part of the brain. Its shape is roughly circular.

The functions of the putamen depend on the neurotransmitters GABA and acetylcholine, as well as enkephalin, an opioid peptide involved in pain perception and its regulation. For its part, gamma-aminobutyric acid or GABA is the main inhibitory neurotransmitter, while acetylcholine (ACh) activates muscle movement.

• You may be interested: "GABA (neurotransmitter): what it is and what role does it play in the brain"

Structure and anatomy

The putamen, the striated body, the pale balloon, the caudate nucleus, the nucleus accumbens, the subthalamic nucleus, the substantia nigra, and the red substance form the basal ganglia. The putamen is the outermost of these nuclei.

The word "ganglion" is normally used to designate groups of neuronal cells that are located in the system. peripheral nervous system, so the nomenclature is paradoxical in this case, as the basal ganglia are located in the brain.

Morphologically and functionally the putamen is intimately related to the caudate nucleus, globus pallidus, and nucleus accumbens; as a whole, these three structures are known as the striatum. Likewise, we call the "lenticular nucleus" the junction between the putamen and the globe pallidus.

The putamen is connected to the substantia nigra and the globe pallus by different nerve pathways. This allows the exchange of information between the basal ganglia and the cerebral cortex, with the thalamus fulfilling its usual function of relay nucleus.

• Related article: "Parts of the human brain (and functions)"

Functions of the putamen

The two main functions of the putamen are regulation of movement and facilitation of different types of learning. It is also involved in disgust and feelings of hatred.

Let's see what are the pathways and mechanisms that allow the putamen to fulfill these functions.

1. Regulation of movement

The putamen and the rest of the structures that make up the striatum send afferences to the brain stem, to the regions of the thalamus involved in movement, and to the motor cortex. These signals ensure that locomotion occurs properly.

Other motor activities related to the putamen include selection of movements, regulation of motor learning and planning of motor sequences. This structure is considered to be important especially for the control of the arms and legs.

However, a motor function is not attributed to the putamen specifically, but this role is due to its connections with other structures, both cortical and subcortical.

2. Operant conditioning

The operant or instrumental conditioning it is a type of learning that is based on the positive (reinforcement) or negative (punishment) consequences of the behavior. Dopaminergic and cholinergic neurons that abound in the basal ganglia play a key role in this regard.

3. Implicit learning

Implicit learning is one that occurs passively, through mere exposure to certain stimuli. Dopamine and acetylcholine are believed to account for this function of the putamen, as does operant conditioning.

4. Learning categories

Scientific research suggests that the putamen also influences category learning, that is, broad psychological constructs that include other more specific ones. For example, the category "animal" encompasses the concepts "elephant", "fish" and "fox".

• Related article: "The 8 higher psychological processes"

5. Disgust, contempt and hatred

It has been theorized that the putamen is involved in feelings of disgust and contempt due to its connections with the insula; this route is known as the "hate circuit". In addition, it is believed that the putamen is also part of the motor system that acts as a consequence of these emotions.

Related disorders

Injuries to the putamen cause involuntary movements such as tremors, sudden spasms, or chores (rapid shaking of the feet and hands). These types of motor symptoms are very characteristic of damage in the basal ganglia, as well as in the cerebellum, which is functionally related to these nuclei.

Various neurodegenerative diseases cause motor symptoms of this type by destroying tissues of the putamen and other basal ganglia. In particular, the disease of Parkinson's, Huntington's and Lewy body dementia.

Other psychological and neurological disorders associated with the putamen are attention deficit hyperactivity disorder, Tourette syndrome, schizophrenia, obsessive-compulsive disorder, and some types of depression.

Likewise, damage to this structure can cause restless leg syndrome, a disorder characterized by a feeling of discomfort in the lower extremities. When moving them the discomfort is reduced, so that people with this alteration are compelled to shake them. The symptoms appear in a state of rest, making it difficult to fall asleep.