Cause of parkinsonian symptoms: Firing rate, firing pattern or dynamic activity changes?

Malfunctions of the basal ganglia cause movement disorders, such as Parkinson's disease and dystonia. Several models have been proposed to explain the pathophysiology of these disorders: (1) firing rate model: activity imbalance between the direct and indirect pathways changes the mean firing rates of the output nuclei of the basal ganglia and induces hypokinetic or hyperkinetic movement disorders; (2) firing pattern model: oscillatory and/or synchronized activity observed in the diseased basal ganglia disturbs information processing in the basal ganglia, resulting in motor symptoms; (3) dynamic activity model: abnormal neuronal modulations through the hyperdirect, direct and indirect pathways interfere with the sequential, dynamic activity changes, and disrupt the balance between the movement-related inhibition and its surrounding excitation in the output nuclei, leading to motor symptoms. In this mini-review, we will critically discuss the three models.