When acquiring a new habit or skill, an organism is faced with an enormous space of possibilities from which to choose. THE DEGREES OF FREEDOM PROBLEM AND OPTIMAL PERFORMANCE With sufficient practice, both lead to “automaticity” and a resilience against competing actions that might lead to unlearning.

In either instance, after sufficient experience, the need for reward becomes lower and lower. Both habits and skills can leverage reward-based learning, particularly during their initial acquisition. Physical skills are changes in a physical repertoire: new combinations of movements that lead to new capacities for goal-directed action. Habits are consistent behaviors triggered by appropriate events (typically, but not always, external stimuli) occurring within particular contexts. Habits and skills have many common features. The capacity to tie the laces properly is a skill. Tying one’s shoes after putting them on is something we consider a habit-part of a behavioral routine. Without resorting to technical definitions, we all have an intuition of what habits and skills are. Here, we consider relevant physiological properties of the striatum by contrasting two common forms of adaptation found in all mammals: the acquisition of behavioral habits and physical skills. A fundamental question is how these two capacities-(motor behavior and reinforcement-based learning)-relate to each other and what role the striatum and other basal ganglia nuclei have in forming new behavioral repertoires. Interactions between the dopamine-containing neurons of the midbrain and their targets in the striatum are critical to this function. In parallel, however, the basal ganglia, and especially the striatum, are now widely recognized as being engaged in activity related to learning. Pathology within different basal ganglia circuits predictably leads to either hypokinetic or hyperkinetic movement disorders. Whether measured at the neuronal or regional level, the activities of neurons in the basal ganglia correlate with many movement parameters, particularly those that influence the vigor of an action, such as force and velocity. The nuclei and interconnections of the basal ganglia are widely recognized for modulating motor behavior.

In Cold Domain by Anne Fine