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Basic Science
Anatomy
13 notes available
1 Last Minute Review 2 Embryology & Developmental Anatomy 3 Vascular Anatomy 4 Cerebral Cortex 5 Subcortical Nuclei (BG, Thalamus, Hypothalamus) 6 Limbic System 7 Cerebellum 8 Brainstem 9 Cranial Nerves 10 Spinal Cord 11 Motor System 12 Sensory System 13 Peripheral Nerves and Muscles
Basic Science › Anatomy

Subcortical Nuclei (BG, Thalamus, Hypothalamus)

Subcortical Nuclei: Basal Ganglia, Thalamus & Hypothalamus

What You'll Learn

  • Basal ganglia components — striatum (caudate + putamen), lentiform nucleus (putamen + globus pallidus [GPi + GPe]), STN, substantia nigra (SNc/SNr)
  • Direct vs. indirect pathway — direct = facilitates movement (D1), indirect = inhibits movement (D2); dopamine excites D1 direct-pathway MSNs and inhibits D2 indirect-pathway MSNs → both effects reduce GPi/SNr braking → net facilitation
  • Lesion-to-disorder mapping — SNc loss → Parkinson disease; caudate atrophy → Huntington disease; STN lesion → hemiballismus; putamen copper → Wilson disease
  • Thalamic relay nuclei — VPL (body), VPM (face), VL (cerebellum → motor), VA (BG → motor), LGN (vision), MGN (hearing)
  • Thalamic stroke syndromes — Dejerine-Roussy (thalamic pain), paramedian stroke (vertical gaze palsy + memory loss), artery of Percheron (bilateral)
  • Hypothalamic nuclei — lateral = hunger, ventromedial = satiety, anterior = cooling, posterior = heating, suprachiasmatic = circadian, mammillary bodies = memory
  • Internal capsule — anterior limb, genu, posterior limb; somatotopy; lacunar syndromes (pure motor hemiparesis, ataxic hemiparesis)
HighYield Pearls
  • Direct pathway (D1, Gs): cortex → striatum → GPi/SNr (inhibited) → thalamus (disinhibited) → cortex → FACILITATES movement
  • Indirect pathway (D2, Gi): cortex → striatum → GPe (inhibited) → STN (disinhibited) → GPi (excited) → thalamus (inhibited) → SUPPRESSES competing movement
  • Hyperdirect pathway: cortex → STN directly — rapid “STOP” signal; bypasses striatum
  • Parkinson disease: SNc dopaminergic loss → ↓ direct + ↑ indirect → hypokinetic (bradykinesia, rigidity, rest tremor)
  • Huntington disease: loss of striatal medium spiny GABAergic neurons (indirect pathway first) → hyperkinetic chorea; caudate atrophy → boxcar ventricles
  • Hemiballismus: contralateral STN lesion — classic metabolic mimic is nonketotic hyperglycemia (severe hyperglycemia without ketosis/acidosis) with striatal T1 hyperintensity
  • Wilson disease: copper deposition in putamen → face of giant panda (midbrain) + double panda (pons) sign; Kayser-Fleischer rings
  • Artery of Percheron: single thalamoperforator off one P1 → bilateral paramedian thalamic + midbrain infarct → coma + amnesia + vertical gaze palsy
  • Dejerine-Roussy: VPL/VPM thalamic stroke → contralateral sensory loss followed by thalamic pain (burning dysesthesia)
  • VL/VA thalamic nuclei — motor relay (cerebellum → VL; BG → VA); Vim of VL = DBS target for essential tremor
  • Anterior thalamic nucleus — mammillothalamic tract terminus, Papez memory circuit; lesion → anterograde amnesia
  • Mediodorsal nucleus — limbic/prefrontal relay; lesion → Korsakoff amnesia + confabulation (alcoholic thiamine deficiency)
  • Reticular nucleus of thalamus — GABAergic shell that envelops thalamus; participates in thalamocortical oscillations that sustain 3-Hz spike-wave absence discharges
  • Intralaminar/centromedian nucleus — arousal & nociception; DBS target for generalized epilepsy; lesion → altered mental status
  • Hypothalamic lateral nucleus → hunger + arousal (orexin/hypocretin); lesion → anorexia; orexin loss → narcolepsy type 1
  • Ventromedial nucleus → satiety; lesion → hyperphagia, obesity (Fröhlich/Babinski syndrome) + rage
  • Anterior hypothalamus → cooling/heat dissipation (A/C = Anterior Cooling); lesion → hyperthermia
  • Posterior hypothalamus → heat conservation + shivering; lesion → poikilothermia (cold-blooded)
  • SCN → circadian rhythm (driven by retinohypothalamic input); VLPO (preoptic) → GABAergic sleep promotion
  • PVN + SON → magnocellular → ADH + oxytocin to posterior pituitary; lesion → central diabetes insipidus
  • Mammillary bodies → Papez memory; petechial hemorrhages in Wernicke-Korsakoff (thiamine deficiency)
  • Klüver-Bucy syndrome — bilateral amygdala/anterior temporal lesion → hyperorality + hypersexuality + placidity + visual agnosia (HSV encephalitis)
  • Internal capsule posterior limb — corticospinal tract (arm & leg); lacunar stroke → pure motor hemiparesis (face + arm + leg equally)
  • Circumventricular organs (no BBB) — area postrema (vomiting), OVLT & SFO (osmoreception), median eminence, neurohypophysis, pineal
🔍 Quick ReferenceBG / circuits · Thalamic relay · Hypothalamus / lesion
BG / circuits
  • “Face of the giant panda” midbrain + “double panda” pons on T2 → Wilson disease (putaminal copper)
  • Unilateral flinging, large-amplitude proximal limb movements → hemiballismus (contralateral STN lesion)
  • “Boxcar” lateral ventricles + caudate atrophy → Huntington disease (CAG repeat, chromosome 4)
  • T1 striatal hyperintensity in a hyperglycemic patient with chorea → non-ketotic hyperglycemic hemichorea-hemiballismus
  • Resting pill-rolling tremor + cogwheel rigidity + bradykinesia + asymmetric onset → Parkinson disease (SNc dopaminergic loss)
  • Lewy bodies (α-synuclein) in SNc neurons → idiopathic Parkinson disease
  • Kayser-Fleischer rings + low ceruloplasmin + young pt with dystonia/tremor → Wilson disease
  • D1 = Gs (direct, facilitates) / D2 = Gi (indirect, inhibits) → dopamine net facilitates movement via striatum
  • Mesolimbic VTA → NAc → reward / addiction / positive symptoms of schizophrenia
  • Tuberoinfundibular (arcuate → pituitary) → DA inhibits prolactin; D2 blockade → hyperprolactinemia + galactorrhea
Thalamic relay nuclei
  • VPL → body somatosensation (medial lemniscus + spinothalamic → S1)
  • VPM → face somatosensation + taste (trigeminothalamic + solitary tract)
  • VL → motor relay from cerebellum (dentate) → M1; Vim subnucleus = DBS target for essential tremor
  • VA → motor relay from basal ganglia (GPi) → SMA/premotor
  • LGN → vision (retina → optic radiations → V1); 6 layers, M/P streams
  • MGN → audition (inferior colliculus → A1 transverse gyrus of Heschl)
  • Anterior nucleus → Papez memory circuit (mammillothalamic tract input)
  • Mediodorsal → limbic + prefrontal; lesion → Korsakoff amnesia + confabulation
  • Pulvinar → parieto-temporo-occipital association; “pulvinar sign” on FLAIR → variant CJD
  • Centromedian/intralaminar → arousal + nociception; DBS target for refractory generalized epilepsy
  • Reticular nucleus → GABAergic shell; participates in thalamocortical oscillations that sustain 3-Hz spike-wave absence discharges
  • Dejerine-Roussy syndrome → VPL/VPM stroke → contralateral thalamic pain + hemisensory loss
  • Artery of Percheron infarct → bilateral paramedian thalami ± midbrain → coma, vertical gaze palsy, amnesia
Hypothalamus / lesion syndromes
  • Lateral nucleus lesion → anorexia, wasting (“Lateral = Lean”); orexin/hypocretin loss → narcolepsy type 1 + cataplexy
  • Ventromedial nucleus lesion → hyperphagia, obesity, rage (“VentroMedial = Very Much”); craniopharyngioma classic cause
  • Anterior hypothalamus lesion → hyperthermia (loss of cooling; “A/C = Anterior Cooling”)
  • Posterior hypothalamus lesion → poikilothermia / hypothermia (loss of heat conservation)
  • SCN lesion → loss of circadian rhythm; receives retinohypothalamic input
  • VLPO (preoptic) lesion → insomnia (loss of GABAergic sleep promotion); fatal familial insomnia targets thalamus
  • PVN/SON lesion → central diabetes insipidus (ADH loss) ± SIADH from disinhibition
  • Mammillary body petechial hemorrhages → Wernicke-Korsakoff (thiamine deficiency — alcoholics, bariatric, hyperemesis)
  • Arcuate nucleus → POMC (satiety) + NPY/AgRP (hunger); leptin & ghrelin sensing; DA → tuberoinfundibular PRL inhibition
  • Klüver-Bucy syndrome → bilateral amygdala → hyperorality + hypersexuality + placidity + visual agnosia (HSV encephalitis classic)
  • Fröhlich syndrome (adiposogenital dystrophy) → ventromedial/infundibular lesion → obesity + hypogonadism in boys
  • Diencephalic syndrome (Russell) → anterior hypothalamic glioma in child → profound emaciation despite normal intake
  • Pituitary stalk transection → loss of DA tone → hyperprolactinemia (“stalk effect”)
Basal Ganglia Anatomy

Overview & Definitions

  • Basal ganglia — collection of subcortical nuclei deep to cerebral cortex, lateral to the thalamus
  • Primary role: motor control, procedural learning, habit formation, emotion, executive function
  • The basal ganglia do NOT initiate movement — they modulate cortically initiated motor plans

Component Structures

Axial section of the hemisphere showing the basal ganglia and internal capsule
Horizontal (axial) section — the classic basal-ganglia view: head of caudate and putamen (striatum), globus pallidus, and thalamus, with the anterior limb, genu, and retrolenticular internal capsule between them; claustrum and insula lie laterally.© HighYieldNeuro
Structure Components Role
Striatum Caudate nucleus + Putamen INPUT nucleus — receives cortical projections (glutamate); connected across internal capsule by cell bridges giving "striped" appearance
Lentiform nucleus Putamen + Globus pallidus (GPi + GPe) Anatomical grouping — lens-shaped structure lateral to the internal capsule
Globus pallidus externa (GPe) — Intermediate relay in the indirect pathway; GABAergic output to STN
Globus pallidus interna (GPi) — OUTPUT nucleus — tonically inhibits thalamus via GABA; DBS target
Subthalamic nucleus (STN) — Only excitatory (glutamatergic) nucleus in BG; drives GPi activity; DBS target for Parkinson disease
Substantia nigra pars compacta (SNc) — Source of dopamine to striatum (nigrostriatal pathway); lost in Parkinson disease
Substantia nigra pars reticulata (SNr) — OUTPUT nucleus (functionally equivalent to GPi); GABAergic inhibition of thalamus & superior colliculus
Board Pearl

Striatum = INPUT; GPi/SNr = OUTPUT. The internal capsule separates the caudate (medial) from the lentiform nucleus (lateral). Striatal cell bridges crossing the internal capsule give it its "striped" name.

Spatial Relationships & Blood Supply

Coronal section through the internal capsule and basal ganglia
Coronal section through the internal capsule — caudate, lentiform nucleus, and thalamus flank the internal capsule, with the subthalamic nucleus, substantia nigra, and red nucleus below.© HighYieldNeuro

Spatial Organization (Medial → Lateral)

  • Caudate nucleus — C-shaped, follows lateral ventricle (head, body, tail); head bulges into frontal horn
  • Internal capsule — between caudate/thalamus (medially) and lentiform nucleus (laterally)
  • Globus pallidus — medial portion of lentiform nucleus
  • Putamen — lateral portion of lentiform nucleus
  • External capsule — lateral to putamen
  • Claustrum — thin gray matter between external and extreme capsules
  • Extreme capsule — between claustrum and insular cortex

Blood Supply

  • Lenticulostriate arteries (lateral branches of MCA M1) → putamen, globus pallidus, caudate head, internal capsule — most common site of hypertensive hemorrhage
  • Recurrent artery of Heubner (from ACA) → caudate head, anterior limb of internal capsule, anterior putamen
  • Anterior choroidal artery (from ICA) → posterior limb of internal capsule + optic tract + LGN + medial temporal lobe (uncus, hippocampus, amygdala) + medial globus pallidus (GPi)
Clinical Pearl

Hypertensive putaminal hemorrhage is the most common hypertensive intracerebral hemorrhage → rupture of lenticulostriate arteries → contralateral hemiparesis, hemisensory loss, hemianopia, and eyes deviate toward the lesion.

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