Thalamus

Question 1

Thalamic groups and associated nuclei:

Answer 1

Anterior
-Anterior nucleus (AN)

Medial
Medial dorsal nucleus (MDN)

Lateral
-Ventral nuclei
o Ventral anterior nucleus (VA)
o Ventral lateral nucleus (VL)
o Ventroposterior lateral nucleus (VPL)
o Ventroposterior medial nucleus (VPM)
o Lateral geniculate nucleus (LGN)
o Medial geniculate nucleus (MGN)

-Dorsal nuclei:
o Pulvinar

Intralaminar
Centromedian nucleus
Parafascicular nucleus

Question 2

Anterior nuclei Function:

Answer 2

Part of Papez circuit: important for emotional episodic memory
Damage to this area causes disruption of the Papez circuit and therefor loss of emotional episodic memory
o Leads to several diseases:
Alzheimer’s disease
Parkinson’s disease
Korsakoff syndrome: caused by Thiamine (B1)
deficiency

Question 3

Medial dorsal nucleus functin:

Answer 3

Part of the Medial group Involved with:
o Emotions, in particular the emotional aspect of memory
o Motivation o Drive
Damage causes changes in personality, since the patient loses their motivation and emotional memory
o Leads to Korsakoff syndrome

Afferents of the medial dorsal nucleus:
o Olfactory cortex: found in the temporal lobe,
processes emotions related to smell
 Example: the good memory we can associate to
the smell of bacon

o Amygdala: part of the limbic system, involved with
emotions such as fear, anxiety, aggression.

o Hypothalamus: also part of the limbic system

Efferent: all this information about e motional memory, motivation, anger and fear is sent from the medial dorsal nucleus to the prefrontal cortex

Question 4

Centromedian nucleus Function:

Answer 4

Part of Intralaminar nuclei
It applies emotional component to pain sensation:
o It receives inputs from the slow pain pathway (spinothalamic pathway):
 The painful stimulus is transmitted by C fibers to the posterior grey horn of the spinal cord → decussation → spinal lemniscus → (reticular formations) → Centromedian nucleus → nonspecific cortical areas
* They are called “nonspecific” because they’re not fully understood
* One of these areas is believed to be the Cingulate gyrus: part of the limbic system, involved with emotions

Question 5

Lateral geniculate nucleus function:

Answer 5

Mnemonic: L of lateral for Light = Vision Part of visual pathway
o Visual stimulus → retina → optic nerve, in particular the median lateral fibers → optic tract → lateral geniculate nucleus → sends to:
 Midbrain
 Primary Visual cortex (BA17), in the occipital
lobe

Question 6

Medial geniculate nucleus function:

Answer 6

Mnemonic: M of medial for Music = Hearing Part of auditory pathway
o Auditory stimulus → vestibulocochlear nerve ( CN VIII) → cochlear nuclei in pontomedullary junction → decussation at trapezoid body → (superior olivary nucleus) → lateral lemniscus → inferior colliculus → inferior brachium → medial geniculate nucleus →
 Gives rise to acoustic radiation → Primary auditory cortex (BA41, 42), in temporal lobe

Question 7

function of Pulvinar

Answer 7

Most posterior nucleus of the thalamus, on the dorsal aspect of lateral group
Afferents:
o Medial geniculate nucleus: carries auditory
information
o Lateral geniculate nucleus: carries visual information o Superior colliculus: involved in reflexes and
coordination of movement between eyes, head and
neck starting from visual information
o Inferior colliculus: involved in reflex and coordination
of head and neck movement based on auditory stimuli.
Efferent: Visual association areas (BA18, 19)
o The Pulvinar is involved in visual processing:
interpretation of an image in order to give it meaning + recognition of objects, faces, expressions…

Question 8

Ventroposterior lateral nucleus (VPL) function:

Answer 8

Afferents:
o Dorsal column – medial lemniscus pathway:
carries proprioception, fine touch and vibration sense from the body
Fine touch/proprioception/vibration stimulus → posterior grey horn → fasciculus gracilis and fasciculus cuneatus → nucleus gracilis and nucleus cuneatus (medulla) → decussation → VPL
o Spinothalamic tract:
Can be further divided in:
* Anterior: carries crude touch and pressure sensations
* Lateral: carries pain and thermic sensations Pain/temperature/crude touch stimulus →
posterior grey horn → decussation →
* To anterior funiculus: makes the anterior
spinothalamic tract
* To lateral funiculus: makes lateral
spinothalamic tract
* → the 2 tracts ascend and fuse together again
→ VPL
Efferent: Primary somatosensory cortex (BA3, 1, 2), in parietal lobe

Question 9

Ventroposterior medial nucleus (VPM) function:

Answer 9

Receives 2 types of information:
o All information from the face (proprioception, pain,
temperature, vibration, touch)
Carried through trigemino-thalamic tract:
* Stimulus from the face → sensory fibers of Trigeminal nerve (CN V) → enter the brainstem at different level to reach the trigeminal nuclei:
o Mesencephalic trigeminal nucleus
o Principal pontine nucleus
o Spinal nucleus of the trigeminal nerve
* From these nuclei → VPM o Gustation:
 From the taste buds, the information is carried by 3 cranial nerves:
* Facial nerve (CN VII): receives information from the anterior 2/3 of the tongue
* Glossopharyngeal nerve (CN IX): receives information from the posterior 1/3 of the tongue
* Vagus nerve (CN X): receives information from epiglottis and oropharynx
These 3 nerves make the Tractus Solitarius, which arrives at the Nucleus Tractus Solitarii (medulla) → central tegmental tract → VPM
Efferent: Primary somatosensory cortex (BA3, 1, 2)

Question 10

Ventral anterior nucleus function:

Answer 10

Most anterior nucleus of the lateral group Afferent: basal ganglia
o The Ventral anterior nucleus is involved in initiation and planning of movement
o Its involved in enhancing or inhibiting a planned movement, through different pathways:
Direct pathway: enhances movement
* Cortex (premotor and primary motor areas,
mainly) → putamen → Globus pallidus internus → ventral anterior nucleus → sends back to cortex to perform the movement
Indirect pathway: inhibits movement
* Cortex → putamen → Globus pallidus
externus → subthalamus → Globus pallidus
internus → ventral anterior nucleus → cortex  An additional station can be the substantia nigra,
found in the midbrain
* Contains many dopaminergic neurons and can
promote both the direct and indirect pathway, depending on what’s needed in a give situation.
Efferent: the ventral anterior nucleus sends information to Premotor cortex (BA6)

Question 11

Ventral lateral nucleus function :

Answer 11

2 functions:
o Coordination of motor movement o Modulation of motor movement
Afferent:
o Basal ganglia:
 Motor cortex → basal ganglia → direct or indirect pathway → ventral lateral nucleus → motor cortex
o Cerebellum:
 Motor cortex → dentate nucleus of cerebellum:
* This nucleus receives different types of information: proprioception, equilibrium from the inner ear, and from the motor cortex
o It elaborates all of them to obtain the best movement to perform in a given situation.
 From the dentate nucleus → (red nucleus) → ventral lateral nucleus
Efferent: Primary motor cortex (BA4), which allows us to perform the proper movement