The basal ganglia downstream control of brainstem motor centres - an evolutionarily conserved strategy

- A large part of the basal ganglia output targets brainstem motor centres directly.
- During initiation of movement both the direct and indirect pathway become active.
- The dopamine system targets brainstem motor centres in addition to the forebrain.
- The organisation of the basal ganglia and habenulae is phylogenetically conserved.

The basal ganglia plays a crucial role in decision-making and control of motion. The output of the basal ganglia consists of tonically active GABAergic neurons, a proportion of which project to different brainstem centres and another part projecting to thalamus and back to cortex. The focus here is on the former part, which keeps the different brainstem motor-centres tonically inhibited under resting conditions. These centres will be disinhibited when called into action. In the control of motion the direct pathway will promote movement and the indirect pathway inhibit competing movement patterns counteracting the motor-command issued. The basal ganglia detailed structure and function are conserved throughout the vertebrate evolution, including the afferent (e.g. habenulae) and efferent control of the dopamine system.