Deep within the forebrain is a large, round structure known as the putamen. It is a paired structure, with one residing in each hemisphere of the brain. The putamen acts as a central hub, interconnected with various brain regions to facilitate communication and coordinate a wide range of functions. This structure is a component of the basal ganglia, which are involved in everything from movement to learning.
Anatomy and Location of the Putamen
The putamen is situated at the base of the forebrain and is the outermost portion of the basal ganglia. It is one of three main nuclei in this group, working alongside the caudate nucleus and the globus pallidus. The putamen and the caudate nucleus are so closely related that they are collectively known as the dorsal striatum. A large fiber tract called the internal capsule separates the putamen from the more medially located caudate nucleus.
Medial to the putamen lies the globus pallidus. These two structures, the putamen and the globus pallidus, together form a lens-shaped structure called the lentiform nucleus. The putamen covers the globus pallidus like a shell. This entire assembly is part of the cerebrum and is connected to the thalamus and various regions of the cerebral cortex, forming complex loops for its function.
Core Functions in Movement and Learning
The putamen’s most well-understood role is in the control of voluntary motor movements. It is involved in multiple stages of movement, including the preparation and execution of actions. The putamen helps to specify the amplitude and sequence of movements, ensuring they are carried out smoothly. For example, studies show that as the extent of a limb movement increases, so does the activity within the putamen.
Beyond motor control, the putamen has a significant function in procedural learning, the process of acquiring skills and habits until they become automatic. This allows individuals to perform complex motor sequences without conscious thought, such as riding a bicycle or driving a car. The putamen helps to encode these motor routines, transforming deliberate actions into a single, fluid habit.
This learning mechanism involves the putamen’s role within neural circuits connecting the cortex, striatum, and thalamus. As a new motor skill is practiced, the putamen becomes more active and facilitates the association between a stimulus, the action, and its outcome. This process relies on the neurotransmitter dopamine, supplied from a midbrain structure called the substantia nigra.
Role in Behavior and Emotion
While involved in motor functions, the putamen also contributes to behavior and emotion. It is part of the brain’s reward system and is involved in reinforcement learning. The putamen’s activity is modulated by reward, which is a foundation of habit formation, including those related to addiction.
The structure is also implicated in processing specific social and emotional cues. Neuroimaging studies show the putamen is active during the processing of social rewards, such as value affirmation and emotional support. It also plays a part in processing certain negative emotions, as its activity has been linked to feelings of anger and retaliation in social interactions.
The putamen is involved in more complex emotional and social behaviors. It has been shown to be involved in the maternal brain’s ability to recognize one’s own infant. The volume of the putamen has also been inversely correlated with the ability to recognize fearful facial expressions, suggesting a role in interpreting emotional states. This demonstrates its functions extend beyond motor control into social cognition.
Association with Neurological and Psychiatric Conditions
Disruptions to the putamen’s structure or function are linked to a range of neurological and psychiatric conditions. Because of its role in motor control, its dysfunction is a feature of several movement disorders. In Parkinson’s disease, the degeneration of dopamine-producing neurons in the substantia nigra leads to a dopamine deficit in the putamen. This deficit impairs the putamen’s ability to regulate movement, resulting in symptoms like tremors, rigidity, and slowed movement (bradykinesia).
Conversely, Huntington’s disease involves the degeneration of neurons within the putamen itself, leading to involuntary, dance-like movements known as chorea. The putamen’s role in the automatic performance of learned movements is also implicated in Tourette syndrome, characterized by involuntary motor and vocal tics. The volume of the putamen has been found to be altered in individuals with Tourette syndrome, often showing an increase.
The putamen’s connections to cognitive and emotional circuits mean its dysfunction is also associated with psychiatric disorders. Reduced putamen volume has been observed in individuals with major depression and is linked to symptoms like apathy. Conditions like Obsessive-Compulsive Disorder (OCD) and addiction are also tied to the putamen’s function in habit formation and reward processing. In some cases of OCD and certain substance use disorders, an enlarged putamen volume has been reported.