Dopaminergic reinforcement in the motor system: Implications for
Parkinson’s disease and deep brain stimulation
Abstract
Millions of people suffer from dopamine-related disorders spanning
disturbances in movement, cognition and emotion, often attributed to
changes in striatal dopamine function. Understanding how dopamine
signaling in the striatum and basal ganglia shapes human behavior is
fundamental to advancing the treatment of affected patients.
Dopaminergic neurons innervate large scale brain networks and many
different roles for dopamine signals have been proposed, such as
invigoration of movement and tracking of reward contingencies. The
canonical circuit architecture of cortico-striatal loops sparks the
question, whether dopamine signals in the basal ganglia serve an
overarching computational principle which could provide new insights
into symptom generation in psychiatry to neurology. Here, we review the
perspective that dopamine could bidirectionally control neural
population dynamics, increasing, or decreasing their strength and
likelihood to reoccur in the future, a process previously termed neural
reinforcement. We outline how the basal ganglia pathways could drive
strengthening and weakening of circuit dynamics and discuss the
implication of this hypothesis on the understanding of motor signs of
Parkinson’s disease (PD), the most frequent dopaminergic disorder. We
propose that loss of dopamine in PD may lead to a pathological brain
state where repetition of neural activity leads to weakening and
instability, possibly explanatory for the fact that movement in PD
deteriorates with repetition, as defined by the sequence effect or
decrement of movement. Finally, we speculate on how therapeutic
interventions such as deep brain stimulation (DBS) may be able to
reinstate reinforcement signals and thereby improve treatment strategies
of PD in the future.