The putamen is a large, rounded structure deep inside the brain that plays a central role in movement control, learning from rewards, and forming habits. It sits within a group of interconnected structures called the basal ganglia, which act as a relay system between the brain’s outer cortex and its deeper motor centers. Though most people have never heard of it, the putamen is involved in everything from riding a bike to deciding whether to repeat a choice that worked out well last time.
Where the Putamen Sits in the Brain
The putamen is located near the center of the brain, nestled alongside two neighboring structures: the caudate nucleus and the globus pallidus. A thick band of nerve fibers called the internal capsule separates the putamen from the caudate nucleus, though small bridges of cells cut across that barrier to connect them. Together, the putamen and globus pallidus form what anatomists call the lenticular nucleus, a lens-shaped mass visible on brain scans.
Despite being physically separated from the caudate nucleus, the putamen shares a similar cell composition and is often grouped with it under the name “striatum.” This distinction matters because the striatum is where most of the action happens in the basal ganglia. It receives incoming signals from the cortex and filters them before passing instructions along to structures that fine-tune movement and behavior.
How the Putamen Controls Movement
The putamen’s best-understood job is motor control. It sits at the center of what neuroscientists call the “motor loop,” a circuit that connects movement-planning areas of the cortex to the basal ganglia and back again. When you reach for a coffee cup or shift your weight while walking, the putamen helps coordinate the timing and force of those movements. Disrupting the back portion of the putamen in animal studies reliably slows movement down, consistent with the fact that this region receives heavy input from the brain’s motor and sensory cortices.
The putamen is also critical for learning motor skills through repetition. When you first learn to type or play a chord on a guitar, the movements require conscious attention. Over time, as the putamen encodes the sequence, those actions become automatic. This shift from deliberate effort to fluid habit is one of the basal ganglia’s signature contributions to daily life.
Decision-Making and Reward Learning
Beyond movement, the putamen helps you learn from outcomes. Research in primates has shown that when the putamen is temporarily inactivated, subjects lose the ability to make optimal choices based on recent experience. They can still follow simple rules like repeating a choice that just paid off or switching away from one that didn’t. But when they need to integrate the results of multiple past actions to figure out which option is best, performance falls apart.
This points to a specific role: the putamen tracks the value of different actions based on what happened before and updates those values over time. It essentially keeps a running scorecard, combining information about which actions you tried and what rewards followed, then uses that history to guide your next move. This process depends heavily on dopamine, a chemical messenger that signals reward and motivation throughout the striatum. Dopamine acts on two types of receptors in the putamen, and the balance between them shapes whether a particular behavior gets reinforced or suppressed.
Emotional and Social Functions
The putamen isn’t purely a motor or reward structure. Brain imaging studies have linked it to emotion regulation, particularly in social situations. In experiments where participants played cooperative games while experiencing anger, activation of the left putamen was associated with higher cooperation rates and lower self-reported anger toward a partner. This suggests the putamen may help suppress disruptive emotions so that goal-directed behavior can proceed, a function that fits neatly with its broader role in selecting actions based on expected outcomes rather than raw impulse.
The Putamen’s Chemical Environment
The putamen runs on two key chemical messengers. Dopamine, released by neurons projecting up from the brainstem, is essential for signaling reward and driving learning. GABA, the brain’s primary inhibitory messenger, is produced by about 90% of the putamen’s neurons. These GABA-producing cells, called medium spiny neurons, are the putamen’s workhorses. They receive cortical input, process it, and send inhibitory signals onward to other basal ganglia structures.
The interplay between dopamine and GABA sets the tone for how the putamen operates. Dopamine release in the putamen is kept in check by a background level of GABA inhibition, regulated in part by surrounding support cells called astrocytes. When this balance shifts, either through disease or drugs, the consequences for movement and motivation can be profound.
What Happens When the Putamen Is Damaged
Because of its rich blood supply and deep location, the putamen is one of the most common sites for a type of stroke caused by high blood pressure. These hemorrhages can range enormously in severity. A small bleed may produce no noticeable symptoms at all, while a large one can extend into the surrounding white matter and fluid-filled ventricles of the brain, causing significant disability. The symptoms at onset and the long-term outcome depend almost entirely on how much bleeding occurs.
In Huntington’s disease, the putamen gradually loses its medium spiny neurons, the same GABA-producing cells that make up the vast majority of its population. Interestingly, larger neighboring neurons that use a different chemical messenger are spared until late in the disease. The caudate nucleus tends to shrink before the putamen in early Huntington’s, but both structures deteriorate as the disease progresses, contributing to the characteristic movement problems and cognitive decline.
Putamen Changes in ADHD and Addiction
Structural brain imaging has revealed that the putamen looks different in people with certain psychiatric and behavioral conditions. In ADHD, the left putamen tends to be smaller compared to healthy controls. In substance use disorders, the pattern reverses: the left putamen is actually larger than normal. A direct comparison between the two groups confirmed this contrast, with the ADHD group showing significantly less putamen volume than the substance use group. These differences likely reflect distinct disruptions in the dopamine-driven reward circuits that pass through the putamen, though they manifest in opposite structural directions.
How the Putamen Changes With Age
The putamen shrinks steadily over a lifetime. An MRI study of 36 healthy volunteers found a strong correlation between advancing age and decreasing putamen volume, with the caudate nucleus following a similar but slightly less dramatic pattern. This gradual loss of tissue likely contributes to the subtle motor slowing and reduced adaptability in learning new skills that most people experience as they get older. The shrinkage is a normal part of aging, distinct from the accelerated atrophy seen in neurodegenerative diseases.