The brain, a remarkably intricate organ, governs all our thoughts, emotions, and actions. This article explores the dorsolateral striatum, a brain area that plays a significant role in how we learn, move, and form habits.
Understanding the Dorsolateral Striatum
The striatum is a collection of interconnected nuclei located deep within the brain, forming a major part of the basal ganglia. This structure is broadly divided into two main sections: the ventral striatum and the dorsal striatum. The dorsal striatum is further subdivided into the dorsomedial striatum and the dorsolateral striatum (DLS).
The DLS is a sub-region of the dorsal striatum. The dorsal striatum comprises the caudate nucleus and the putamen. The DLS receives projections from the sensorimotor cortex, making it a hub for processing information related to action and habit. This positions the dorsolateral striatum as an important area for controlling movements and forming learned behaviors.
Key Functions of the Dorsolateral Striatum
The dorsolateral striatum is involved in how behaviors transition from conscious control to automatic habits. Initially, actions are often goal-directed, performed with a specific outcome. As these actions are repeated, the DLS contributes to their transformation into responses automatically triggered by environmental cues, becoming less reliant on conscious thought. For example, automatic movements involved in typing or tying shoelaces exemplify how the DLS facilitates the development of such routine behaviors.
Beyond habit formation, the DLS contributes to motor control and procedural learning. It helps in coordinating movements and in acquiring skills that become automatic over time. This includes activities like riding a bicycle, playing a musical instrument, or driving a car. The DLS contains cell ensembles that exhibit bursts of activity at the initiation of well-learned action sequences.
The DLS also integrates reward information within learned routines, reinforcing behaviors that lead to positive outcomes. While the ventral striatum is more associated with initial reward processing, the DLS’s involvement strengthens the association between stimulus and response through this reward-guided learning once a behavior becomes habitual. This contributes to the persistence of habits, even when the initial motivation or reward may no longer be explicitly present.
Dorsolateral Striatum and Neurological Conditions
Dysfunction or damage to the dorsolateral striatum is implicated in several neurological and psychiatric conditions. In Parkinson’s disease, the DLS plays a role in the characteristic motor symptoms. The degeneration of dopamine-producing neurons in the substantia nigra leads to impairments in motor control, causing tremors, rigidity, and slowed movements.
The DLS is also involved in the development of addiction, particularly in the shift from goal-directed drug use to compulsive, habit-like behaviors. As individuals repeatedly engage in substance use, the control over drug-seeking behavior transitions from areas involved in reward to the DLS, contributing to the automatic and often uncontrollable nature of addictive behaviors, even when the initial pleasure diminishes.
The DLS is involved in obsessive-compulsive disorder (OCD). This condition is characterized by repetitive thoughts and ritualistic behaviors, which share similarities with the compulsive, habit-driven actions seen in addiction. While research continues to unravel the precise mechanisms, dysfunction in the DLS and its circuits is thought to contribute to the inflexible and repetitive behaviors observed in individuals with OCD.