Diencephalon: Structure and Function

Question 1

Location of the Diencephalon

Answer 1

Embryologically between the telencephalon and mesencephalon
Between cerebral cortex and brainstem
Medial to internal capsule
Divided in the midline by the third ventricle

Question 2

Diencephalic Subdivisions

Answer 2

Epithalamus 
Dorsal thalamus
Ventral thalamus
Subthalamus
Hypothalamus

Question 3

Epithalamus consists of:

Answer 3

Habenula, Pineal Gland, Posterior Commissure

Question 4

Dorsal Thalamus (or Thalamus) consists of:

Answer 4

Thalamic nuclei, External Medullary Lamina, Internal Medullary Lamina

Question 5

Ventral Thalamus consists of:

Answer 5

Reticular Nucleus of the Thalamus

Ventral Lateral Geniculate Nucleus (vLGN)

Question 6

Subthalamus consists of:

Answer 6

Zona Incerta
Subthalamic Nucleus (of Luys)

Question 7

Hypothalamus consists of:

Answer 7

Hypothalamic nuclei, Infundibulum, Hypophysis (pituitary gland), Hypophyseal portal system

Question 8

Blood Supply of the Thalamus

Answer 8

Anterior communicating artery
Posterior communicating artery 
ACA
PCA
Internal Carotid Artery

Question 9

What are some functions of the thalamus??

Answer 9

“Gateway to the cortex”

1. Relays all sensory information to the cerebral cortex
2. Relays information about motor activities to the cerebral cortex
3. Integrates sensory information from different modalities and projects to association cortex
4. Relays emotional and affective information to the cortex
5. Part of “Papez Circuit” of the limbic system, projects to limbic cortex
6. Intimately involved in the control of alertness, arousal and sleep
7. Under direct cortical feedback and control: reciprocal connections between the thalamus and the cortex

Question 10

Afferent Input, Efferent Output and Function of Anterior Nuclear Group

Answer 10

Afferent: Mammillary Body
Efferent: Cingulate gyrus
Functions: Limbic

Question 11

Afferent Input, Efferent Output and Function of Ventral Anterior

Answer 11

Afferent: Globus Pallidus
Efferent: Premotor Cortex (area 6)
Functions: Motor

Question 12

Afferent Input, Efferent Output and Function of Ventral Lateral

Answer 12

Afferent: Dentate nucleus of cerebellum
Efferent: Motor and premotor (areas 4 and 6)
Functions: Motor

Question 13

Afferent Input, Efferent Output and Function of Ventral Posterior Lateral

Answer 13

Afferent: Dorsal column-medial lemniscus and spinothalamic
Efferent: Somatosensory cortex (areas 3, 1, 2)
Functions: Somatic sensation (body)

Question 14

Afferent Input, Efferent Output and Function of Ventral Posterior Medial

Answer 14

Afferent: Sensory nuclei of trigeminal nerve
Efferent: Somatosensory cortex (areas 3, 1, 2)
Functions: Somatic sensation (face)

Question 15

Afferent Input, Efferent Output and Function of Lateral geniculate

Answer 15

Afferent: Retinal Ganglion Cells
Efferent: Primary Visual Cortex (area 17)
Function: Vision

Question 16

Afferent Input, Efferent Output and Function of Medial geniculate

Answer 16

Afferent: Inferior colliculus
Efferent: Primary auditory cortex (areas 41, 42)
Function: Audition

Question 17

Afferent Input, Efferent Output and Function of Lateral Dorsal

Answer 17

Afferent: Cingulate gyrus
Efferent: Cingulate gyrus
Function: Emotional expression

Question 18

Afferent Input, Efferent Output and Function of Lateral Posterior

Answer 18

Afferent: Parietal cortex
Efferent: Parietal cortex
Function: Emotional expression

Question 19

Afferent Input, Efferent Output and Function of Pulvinar

Answer 19

Afferent: Superior Colliculus, Parietal, Occipital and Temporal lobes
Efferent: Parietal, occipital and temporal lobes (POT)
Function: Integration of sensory information

Question 20

Afferent Input, Efferent Output and Function of Medial Dorsal

Answer 20

Afferent: Amygdaloid nuclear complex, olfactory, hypothalamus
Efferent: Prefrontal Cortex
Function: Limbic

Question 21

Afferent Input, Efferent Output and Function of Midline Nuclei

Answer 21

Afferent: Reticular formation and hypothalamus
Efferent: Basal forebrain
Functions: Limbic

Question 22

Afferent Input, Efferent Output and Function of Intralaminar nuclei: Centro-median, Centro-lateral and Parafascicularis

Answer 22

Afferent: Reticular formation, spinothalamic tract, globus pallidus, and cortical areas
Efferent: Basal ganglia and wide areas of cortex
Function: Role in pain, sleep and wakefulness

Question 23

Afferent Input, Efferent Output and Function of Reticular nucleus

Answer 23

Afferent: Cortex, thalamus, brain stem reticular formation
Efferent: Thalamic nuclei
Function: Modulation of thalamic activity

Question 24

What is Thalamic Syndrome?

Answer 24

Caused by vascular lesion/tumor (rare)
Usually involves damage to the lateral group of thalamic nuclei (VPL)
Initially: contralateral hemianalgesia
Soon: painful sensations appear with noxious stimuli
Later: pain is provoked by pressure, touch and vibration
In time: state of spontaneous, constant or paroxysmal pain is evoked on the affected side (contralateral to the lesion) without any external stimulus (Dysesthesia)
Threshold for pain, temp and tactile sensate is usually raised on the affected side – but once the threshold is reached, pain has a strong emotional overtone to it.