Basal Ganglia Pathways

DIRECT · INDIRECT · LIVE CIRCUIT STATE

Normal
Dopamine (SNc)
Striatal dopamine100%
0100200
100% = normal · drag to model loss or excess
Clinical presets
Interventions
⚡STN lesion
◉STN-DBS (130 Hz)
✕GPi lesion (pallidotomy)
▽D2 neuron loss (HD)
Direct pathway Indirect pathway Glu + Glu + DA + DA − GABA · SP − GABA − GABA · Enk − GABA − Glu + GABA − Glu + Glu + Cortex SNc baseline SNc baseline Striatum D1 · direct baseline D2 · indirect baseline ACh GPe baseline STN baseline GPi / SNr baseline GPi / SNr baseline Thalamus (VA / VL) baseline ↓ To cortical motor areas
Movement output
hypokineticnormalhyperkinetic
Normal movement

Normal

Dopamine balances the two pathways. The direct pathway briefly silences GPi to release the thalamus and permit movement; the indirect pathway raises GPi to suppress unwanted movement. Net thalamic output sits at baseline.

Circuit readout

Tap any nucleus

Select a box in the circuit to see its role and what is happening to it in the current state.

How to read the circuit
Bright + glowing = hyperactive
Solid = activated
Dim = baseline
Faded = inhibited
Dashed/ghost = silenced
disinhibbrake removed → released
Excitatory (Glu, DA→D1)
Inhibitory (GABA, DA→D2)
Circuit layout adapted from Blumenfeld H, Neuroanatomy Through Clinical Cases (Sinauer Associates / Oxford University Press). Diagram redrawn and made interactive for teaching; not the original figure.