Basal Ganglia Pathways

Direct Pathway = Disinhibition of the Thalamus

• Motor Cortex excites the Striatum (cauduate nucleus and putamen)

• Leads to inhibitory signals to the Globus pallidus internal

• Also leads to inhibitory signals to the Substantia Nigra pars reticulata/reticularis

• In the mean time, Substantia Nigra pars compacta = dopaminergic signalling to Striatum via D1 receptors

• Further enhances Inhibitory signal of Striatum and Pars reticulata

• VA/VL nuclei of Thalamus = excited = talks back to cortex

• Ultimately resulting in Muscle movement

Indirect Pathway = Dampening down signal (less movement = fine-tuning to prevent overstimulation probably)

• Motor Cortex excites the Striatum (cauduate nucleus and putamen)

• Leads to inhibitory signals to the Globus pallidus external

• Leads to disinhibition of Subthalamic nuclei

• Subthalamic Nucleus = excites Pars reticulata and globus pallidus internal

• Leads to inhibition of Thalamus = lowers output = less movement

• In the mean time, Pars compacta = dopamine signalling via D2 receptors to enhance inhibition of globus pallidus externa