NEUR 334 Thalamus

What is the thalamus (structure + location)

A massive group of bilateral nuclei in the diencephalon, oval-shaped, embedded in white matter

What is the core functional identitiy of the thalamus ?

A relay station with reciprocal connections to the cortex

What is the anterior boundary of the thalamus

Interventricular foramen of Monroe

What is the posterior boundary of the thalamus

Posterior Commisure

What is the inferior boundary of the thalamus

Hypothalamic sulcus

What is the superior boundary of the thalamus

Forms part of the floor of the lateral ventricle

What is the lateral boundary of the thalamus

Internal Capsule

What is the medial boundary of the thalamus

Forms lateral wall of the 3rd ventricle

What are the FOUR major roles of the thalamus

1. Process sensory information → cortex

2. Regulates motor program execution (basal ganglia)

3. Controls cortical excitability (from reticular formation!)

4. Influnces emotional and motivational responses (limbic system)

Which brain regions provide motor input to the thalamus

Basal Ganglia

Cerebellum

What structure divides the thalamus anatomically?

Internal medullary lamina

What are the three functional categories of thalamic nuclei?

1. Relay nuclei (most of the thalamus)

2. Subcoritcal nuclei (internuclear)

3. Intralaminar (ARAS)

What are the 5 anatomical groups of thalamic nuclei?

1. Anterior

2. Medial

3. Lateral

4. Intralaminar

5. Reticular

What nucleus makes up the anterior group

Anterior nucleus

What nucleus is in the medial group?

DORSOMEDIAL (MD) nucleus

What are the dorsal teir nuclei of the lateral group of the thalamus

• LD

• LP

• Pulvinar

What are the ventral tier nuclei of the lateral group?

• VA/VL

• VPL/VPM

• LGN/MGM

Where are the intralaminar nuclei located?

In the internal medullary lamina

Where is the reticular nucleus located

Between the

• external medullary lamina

• internal capsule

Label this diagram

What tiers does the lateral group of the thalamus divide to , and what are the subregions of these teirs

What is the key rule of thalamocortical connections

They are reciprocal (cortex ←→ thalamus)

A key rule for thalamic prohections is that they’re either focal or diffuse, what is the difference between focal vs diffuse

Focal → specific region of the cortex

Diffuse → widespread association cortex

Where does VA/VL send their connections to

VA → frontal cortex

VL → Motor and premotor cortex

What thalamus subdivisions share connections with the cingulate gyrus

Anterior gorup

LD

What thalamus subdivision shares connections with the prefrontal cortex (PFC)

MD

Which thalamic subdivision share connections with Intralaminar nuclei

Widesprea cortical regions (all over to keep you awake)

What thalamic subdivision share connections with Parieto-occipital cortex

Pulvinar and LP

What thalamic subdivisions share connections with somatosensory cortex

VPM and VPL

Which thalamic subdivision recieves input from the spinal cord (medial leminiscus, spinothalamic tracts)

VPL

Which thalamic subdivision get inputs from the head AND neck (trigemial leminiscus, trigeminothalamic tract, gustatory input)

VPM

What are the afferent fibers that send inputs to anterior nucleus of the thalamus

• Limbic system

• Hippocampus for LD

• Hypothalamus & cingulate gyrus

What are the efferent fibers that send output FROM the anterior nucleus

Cingulate gyrus

What is the function of the dorsomedial nucleus of the thalamus

Cognitive and higher limbic functions

Where does the dorsomedial nucleus recieve afferent fibers from

1. Olfactory cortex

2. Parts of the limbic system

3. Prefrontal and orbital cortices

Where does the dorsomedial nucleus send efferent fibers to

1. Frontal and orbital cortices

2. Hypothalamus

3. Basal Forebrain

What is the funciton of the dorsal tier nuclei (Pulvinar & LP)

Complex visual and language processing

Where do pulvinar & LP recieve afferent fibers FROM

1. Parietal, temporal, and occipital cortices

Pulvinar (SPECIFICALLY)

2. Superior colliculus + tectum

Where do pulvinar & LP send efferent fibers to

1. Parietal

2. Temporal

3. Occipital

What is the function of Ventral Anterior (VA) and ventral lateral (VL) nuclei?

Regulat execution of motor programs

Where do VA/VL recieve afferent fibers FROM?

1. Globus pallidus of the basal ganglia

2. Supllementary motor cortex for VA

3. Pre, motor cortex & cerebellum for VL

Where does VA send efferent fibers TO?

Supplementary motor cortex

Where does the VL send efferent fibers to

Premotor + motor cortex

What is the funciton of the ventral posterior nucleus?

Regulates incoming somatosensory information

Where does ventral posterior send afferent fibers from

Ascending somatosensory pathways

Where does ventral posterior send efferent fibers TO?

Primary somatosensory cortex (postcentral gyrus)

What is the difference between VPL and VPM inputs

VPL → trunk and limbs

VPM → head, neck, and face

What is the funciton of the medial and lateral geniculate nuclei (MGN/LGN)

MGN → auditory

LGN → visual

What is the fucntion of intralaminar nuclei?

Control level of cortical activity

Where do intralaminar nuclei recieve afferent fibers FROM?

1. Reticular formation

2. Frontal & patietal cortex

3. Motor Pathways

Where od intralaminar ueclei send efferent fibers TO?

1. Frontal cortex

2. Parietal cortex

3. Neostriatum (basal ganglia)

What is the function of the reticular nucleus?

Inhibitory modulation of thalamic activity

Where does the reticular nucleus recieve afferent fibers from

• Cerebral Cortex

• Most thalamic areas

Where does the reticular nucleus send efferent fibers TO?

Thalamic relay neurons

What is unique about reticular nucleus outputs?

No direct projection to cortex (not a relay nucleus)