Thalamus

Question 1

Thalamus

Functions

Answer 1

Relay site for sensory and motor systems to cerebral cortex.

Sensory info from spinal cord, brainstem, and optic nerves.

involved in arousal, sleep, and attention

Motor info from basal ganglia and cerebellum.

Question 2

Thalamus

Subdivisions

Answer 2

Dorsal thalamus:

Dorsal and medial subdivisions

Anterior, medial, and lateral nuclei

Ventral thalamus:

Reticular and subthalamic nuclei

-Associated with basal ganglia

Question 3

Thalamic

Organization

Answer 3

• Massa intermedia ⟾ divides medially
• EML ⟾ lateral boundaries
• IML ⟾ internal division into 3 sectors:
  
  • Anterior
  • Medial
  • Lateral
    
    • Dorsal tier
      
      • lateral dorsal (LD)
      • lateral posterior (LP)
      • pulvinar
    • Ventral tier
      
      • ventral anterior (VA)
      • ventral lateral (VL)
      • ventral basal complex
        
        • ventral posterior lateral (VPL)
        • ventral posterior medial (VPM)
• LGN and MGN form bumps on caudal pole

Question 4

Specific/Relay

Nuclei

Answer 4

Receives single sensory modality or input from a distinct part of the motor system.

Projects to a specific location of the cerebral cortex.

Receives reciprocal input from cortex.

Includes:

• LGN
• MGN
• Ventrobasal complex
  
  • Ventral posterior lateral nucleus (VPL)
  • Ventral posterior medial nucleus (VPM)
  • Ventral posterior inferior nucleus (VPI)
• Anterior nucleus (AN)
• Ventral lateral nucleus (VL)
• Ventral anterior nucleus (VA)

Question 5

Lateral Geniculate Nucleus

(LGN)

Answer 5

retinal ganglion cells → optic nerve → optic chiasm → LGN → primary visual cortex

• Partial crossing @ chiasm ⟾ LGN receives b/l input
  
  • topographically organized
• Six-layered nucleus
  
  • contralateral eye ⟾ 1,4,6
  • ipsilateral eye ⟾ 2,3,5
  • layers 1 and 2 ⟾ motion
  • layers 3-6 ⟾ dorsal parvocellular layers ⟾ color

Question 6

Medial Geniculate Nucleus

(MGN)

Answer 6

Bilateral auditory input → inferior colliculus → MGN → primary auditory cortex

Info tonotopically organized

Question 7

Ventral Posterior Lateral Nucleus

(VPL)

Answer 7

Epicritic sensation contralateral body:

cuneate and gracilis n. → medial leminiscus → dorsal columns system → VPL → 1° somatosensory cortex

Protopathic sensation contralateral body:

STT → VPL → 1° somatosensory cortex

• Labeled lines:
  
  • medial lemniscal or STT neuron projects to modality specific neuron in the VPL
  • some neurons are multimodal

Question 8

Ventral Posterior Medial Nucleus

(VPM)

Answer 8

From face, oral/nasal cavities, and scalp:

Chief sensory n. of V (epicritic) → medial leminiscus → VPM

Spinal trigeminal n. (protopathic) → STT → VPM

Solitary n. (gustatory) → central tegmental tract→ VPM (most medial)

VPM → primary sensory cortex

Question 9

Ventral Posterior Inferior Nucleus

(VPI)

Answer 9

Located between VPL and VPM.

Vestibular nuclei → VPI → postcentral gyrus.

Question 10

Lateral Dorsal

(LD)

Answer 10

Relay nucleus

Hippocampus → LD → cingulate gyrus.

Function unclear.

Question 11

Anterior Nucleus

(A)

Answer 11

Mostly ipsi mammillary body → mammillothalamic tract → A → cingulate cortex

Part of the Papez circuit of limbic system.

Functions:

Learning, memory, emotion.

Question 12

Ventral Lateral Nucleus

(VL)

Answer 12

Cerebellum > basal ganglia → VL → primary motor and premotor cortex.

Subdivisions associated with specific input/output:

• Ipsi basal ganglia (globus pallidus interna & substantia nigra reticulata) → rostral/oral VL → premotor cortex
• Contralateral cerebellum (deep nuclei) → medial VL → primary motor cortex

Functions in movement control and planning.

Question 13

Ventral Anterior Nucleus

(VA)

Answer 13

Basal ganglia > cerebellum (ipsi globus pallidus interna & substantia nigra reticulata) → VA → premotor and supplementary motor

Functions in movement planning.

Question 14

Dorsal Medial or Medial Dorsal

Nucleus

(DM or MD)

Answer 14

Amygdala, prefrontal cortex & olfactory structures → MD → broadly to prefrontal cortex.

Functions in emotion, cognition, learning, and memory.

Question 15

Lateral posterior nucleus

(LP)

Answer 15

Association nuclei.

Parietal lobe → LP → posterior parietal association cortex.

Functions in sensory integration.

Question 16

Pulvinar

(Pu)

Answer 16

Association nuclei.

Inputs: parietal/occipital/temporal lobes, pretectum, visual cortex, superior colliculus

Projects to occipital, parietal, and temporal lobes.

Functions in sensory integration, perception, language.

Question 17

Intralaminar Nucleus

(IL)

Answer 17

Scattered nuclei within IML & massa intermedia.

Anterolateral system → IL → broad thalamo-cortical projections.

• Centromedian nucleus (CM) largest
  
  • associated w/ basal ganglia
  • input from many sources
    
    • globus pallidus
    • hypothalamus
  • projects mainly to motor cortex

Question 18

Reticular Nucleus

Answer 18

Sheet of cells between EML and internal capsule.

Surrounds most of the rostral, ventral, and lateral surfaces of the dorsal thalamus.

Gateway for info between dorsal thalamus and cortex.

• Receives excitatory collaterals from thalamocortical/corticothalamic axons of all thalamic nuclei
  
  • inhibits in topographic manner all nuclei of the dorsal thalamus (GABA)
• Receives input from brainstem and basal forebrain reticular formations
  
  • related to arousal

Question 19

Thalamic Pain Syndrome

Answer 19

Severe neurological pain d/t lesion of dorsal thalamus or anterolateral system.

There may be associated contralateral hemianesthesia.

Question 20

Thalamus

Caudal Most Portion

Answer 20

Question 21

Thalamus

Mid-Caudal

Answer 21

Question 22

Mid-Thalamus

Answer 22

Question 23

Rostral Thalamus

Answer 23