Fine structure of the thalamus (+ lecture 12)

Question 1

I. Basics
1. Location of thalamus

Answer 1

Thalamus is located in the diencephalon (between the cerebrum and the midbrain). Left and right diencephalon are divided by the 3rd ventricle.

Question 2

I. Basics
2. What are the 5 parts of thalamus?

Answer 2

1. Thalamus
2. Hypothalamus
3. Epithalamus
4. Metathalamus
5. The sub thalamus

Question 3

I. Basics
3. What are the characteristics of Hypothalamus?

Answer 3

Hypothalamus is located below the thalamus,
border between them is the hypothalamic sulcus
- The pituatiry is connected to the hypothalamus with the infundibular recess (pituitary does not belong to the diencephalon)

Question 4

I. Basics
4. What are the characteristics of epithalamus?

Answer 4

The epithalamus consists of pineal
body, habenulae, the white matter
trigonum habenulae, grey matter habenular nuclei, stria medullaris, habenular commissure

Question 5

I. Basics
5. What are the characteristics of Metathalamus?

Answer 5

The Metathalamus consists of the medial geniculate and lateral geniculate bodies. Both of them are located in the lateral part (not visible on picture)

Question 6

I. Basics
6. What are the characteristics of subthalamus?

Answer 6

The subthalamus is located between the thalamus and hypothalamus. Consists of the subthalamic nucleus and zona incerta

Question 7

II. Explain State-dependent modes of relay cell function

Answer 7

1. Reticular thalamic nucleus does not project to cerebral cortex, but to the relay nuclei of the thalamus
2. Reticular nucleus has GABA as its transmitter and is driven by descending input from the cerebral cortex and ascending reticular activating system
3. Reticular nuclear inputs switch on/off the modes of the relay neurons, so they transfer information while we
   are awake and not asleep

Question 8

II. CONNECTIONS AND FUNCTIONS OF THALAMIC NUCLEI
1. What are the Specific sensory relay nuclei?

Answer 8

1. VPL
2. VPM

Question 9

II. CONNECTIONS AND FUNCTIONS OF THALAMIC NUCLEI
2. What is the role of VPL?

Answer 9

• Relays sensory inputs from the body to the cerebral cortex
• Receives input from ascending pathways: spinothalamic tract (spinal cord) and medial lemniscus (dorsal column nuclei = gracile + cuneate)
• Both pathways delivers information on
  proprioception (touch, pressure, vibration, pain,
  temperature) to the VPL nucleus, which in turn
  projects towards postcentral gyrus, where
  primary somatosensory cortex (Br. 3,1,2) is
  located

Question 10

II. CONNECTIONS AND FUNCTIONS OF THALAMIC NUCLEI
3. What is the role of VPM?

Answer 10

• Relays sensory inputs from the head to the
  cerebral cortex
• Receives input from the trigeminal lemniscus and the dorsal trigeminal lemniscus pathways
• Also, projects towards primary sensory cortex in the postcentral gyrus
  => Project to a more lateral part of the gyrus than VPL

Question 11

II. CONNECTIONS AND FUNCTIONS OF THALAMIC NUCLEI
4. List Specific motor relay nuclei

Answer 11

Ventral anterior nucleus (VA)
Ventral lateral nucleus (VL):

Question 12

II. CONNECTIONS AND FUNCTIONS OF THALAMIC NUCLEI
4A. The role of Ventral anterior nucleus (VA)

Answer 12

• The VA receives most from its input from the basal ganglia (pallidum)
• Projects (efferents) to the premotor cortex = initiation and planning of movemen

Question 13

II. CONNECTIONS AND FUNCTIONS OF THALAMIC NUCLEI
4B. The role of Ventral lateral nucleus (VL)

Answer 13

• The VL receives input from the cerebellum (dentate nucleus)
• Projects to the primary motor cortex, precentral gyrus = modulation and coordination of motor movement)

Question 14

II. CONNECTIONS AND FUNCTIONS OF THALAMIC NUCLEI
5. Metathalamus

Answer 14

• The MGB receive input from the inferior colliculus (vestibulocochlear nerve -> cochlear nuclei -> lateral lemniscus -> inferior colliculus) and goes by efferents to the superior temporal gyrus (primary auditory cortex #41-42)
• The LGB receive input from the retina (optic nerve and tract) and goes by efferents to the striate cortex (occipital lobe, primary visual cortex #17)
• Pulvinar also receive afferents from the MGB, LGB and both colliculi, and goes by efferents to the occipital cortex (#17,18,19) mainly #18-19 (visual association)

Question 15

II. CONNECTIONS AND FUNCTIONS OF THALAMIC NUCLEI
6. Midline and intralaminar nuclei of thalamus

Answer 15

• Midline and intralaminar thalamic nuclei receive ascending input from spinal cord, but not directly
• Spinal cord inputs relay in the reticular formation (either in medulla, pons, midbrain)
• These nuclei are part of the ascending reticular activating system, as they project to
  different parts of the cortex and set the level of cortical alertness
• When these nuclei are damaged in humansthe alertness level of the cortex does
  not reach sufficient level for normal functioning

Question 16

II. CONNECTIONS AND FUNCTIONS OF THALAMIC NUCLEI
7. State-dependent modes of relay cell function

Answer 16

• Reticular thalamic nucleus does not project to cerebral cortex, but to the relay nuclei of the thalamus
• Reticular nucleus has GABA as its transmitter and is
  driven by descending input from the cerebral cortex
  and ascending reticular activating system
• Reticular nuclear inputs switch on/off the modes of the relay neurons, so they transfer information while we are awake and not asleep