Subthalamic Nucleus

Anatomy

• A small lens-shaped nucleus in the ventral diencephalon, below the thalamus and medial to the internal capsule; the substantia nigra lies just beneath it.
• The only glutamatergic (excitatory) nucleus of the basal ganglia.
• Input: cortex (hyperdirect pathway: right IFG, pre-SMA, motor cortex) and GPe; output: GPi, SNr and GPe.
• Motor, associative and limbic subregions from dorsolateral to ventromedial.

Functions

• Response inhibition: fast transmission of the “stop” signal (right IFG → STN).
• Braking during decision conflict: raises the decision threshold when choices become difficult (Frank, 2006).
• Suppresses unwanted movements by exciting the GPi/SNr through the indirect and hyperdirect pathways.

Connections and chemistry

• Cortex (right IFG, pre-SMA, motor cortex) → STN (hyperdirect pathway, glutamate)
• GPe ↔ STN (indirect pathway, beta rhythm)
• STN → GPi and SNr (excitatory output)
• Glutamate (output), GABA (input)

Development

Developmental course through childhood and adolescence.

• Response inhibition (stop-signal reaction time) develops markedly from childhood to adolescence; linked to maturation of the fronto-subthalamic network.

Clinical

• ADHD: difficulty with response inhibition; differences in the right IFG–STN network have been reported.
• OCD: STN deep brain stimulation has been studied in adult refractory OCD (Mallet et al., 2008).
• In Parkinson’s disease, STN deep brain stimulation improves motor symptoms; impulsivity and hypomania appear as side effects in some patients.

Treatment

This region from the perspective of medication, psychotherapy and neuromodulation. Letter badges are evidence levels.

• In Parkinson’s disease, STN deep brain stimulation reduces motor symptoms and medication needs; impulsivity and hypomania can develop in some patients, showing the role of the STN’s “stop” function in decision-making. A
• In refractory OCD, STN stimulation reduced symptoms in a sham-controlled crossover trial (Mallet et al., 2008); adults, a late-line option. B
• In ADHD, methylphenidate increases right IFG activation during response inhibition tasks (fMRI meta-analyses); human evidence for a corresponding effect at the level of the STN is limited. C

Assessment

Neuropsychological tasks and measures that probe this region's function.

• Stop-Signal task (stop-signal reaction time)
• Go/No-Go task
• Movement disorder examination (ballism, chorea)

Lesions and damage

Clinical findings expected with damage or dysfunction.

• Contralateral hemiballismus: sudden, flinging, involuntary arm and leg movements (classically from an STN infarct).

In the model

How this structure is defined in the 3D model, and the data source.

CIT168 subthalamic nucleus probability map (right/left).

References

Full citations for the card; links go to the paper (DOI) or a PubMed search.

1. Frank MJ. Hold your horses: a dynamic computational role for the subthalamic nucleus in decision making. Neural Netw 2006;19(8):1120–1136. DOI: 10.1016/j.neunet.2006.03.006
2. Mallet L et al. Subthalamic nucleus stimulation in severe obsessive–compulsive disorder. N Engl J Med 2008;359(20):2121–2134. DOI: 10.1056/NEJMoa0708514