Thalamus

Neuro 102 Thalamus Portion

What structures make up the diencephalon?

Hypothalamus, Epithalamus, Subthalamus, Thalamus

Why does the diencephalon sit at the top of the brainstem?

It is displaced due to massive growth of the telencephalon

What is the main role of the hypothalamus?

Center for homeostasis (temperature, hunger, endocrine control)

What two structures make up the epithalamus?

Habenular nuclei and pineal gland

Where is the habenula located?

Rostral to the pineal gland, near the base of the pineal stalk

What are the inputs and outputs of the habenula?

Input: stria medullaris; Output: habenulointerpeduncular tract

What functions is the habenula involved in?

Reward processing, pain modulation, sleep regulation

What do pinealocytes secrete?

Melatonin at night

How is melatonin secretion regulated?

Sunlight inhibits secretion; hypothalamus signals superior cervical ganglion at night to stimulate melatonin

What nuclei are found in the subthalamus?

Subthalamic nucleus (STN) and zona incerta

What is the subthalamic nucleus functionally linked with?

Basal ganglia circuitry

What percentage of the diencephalon does the thalamus make up?

About 80%

What is the major blood supply of the thalamus?

Branches of the posterior cerebral artery

What are the two primary functions of the thalamus?

Relay information to the cortex; process and filter information

What divides the thalamic nuclei?

Internal medullary lamina (Y‑shaped)

What are the three major regions of the thalamus?

Anterior, medial, lateral regions

What structure connects both thalami?

Interthalamic adhesion

What is the main function of the anterior nucleus?

Emotional learning

What is the input to the anterior nucleus?

Hippocampus via mammillary bodies (mammillothalamic tract)

Where does the anterior nucleus project?

Posterior cingulate cortex

What information does the dorsomedial nucleus integrate?

Olfactory, visceral, and somatic information

Where does the dorsomedial nucleus project?

Prefrontal cortex

What functions is the dorsomedial nucleus involved in?

Memory, planning, emotion/affect

What are the ventral nuclei of the thalamus?

VA, VL, VPM, VPL

What is the function of the ventroanterior (VA) nucleus?

Motor relay to motor cortex

What are the inputs to the VA nucleus?

Basal ganglia and cerebellum

What is the function of the ventrolateral (VL) nucleus?

Motor relay; connects to cerebellum and red nucleus

What does the VPL nucleus relay?

Somatosensory information from the body

What pathways feed into the VPL?

Medial lemniscus (body) and spinothalamic tracts

What does the VPM nucleus relay?

Somatosensory information from the face

What pathways feed into the VPM?

Medial lemniscus (face) and trigeminal/spinothalamic pathways

Which nuclei make up the dorsal tier of the thalamus?

Lateral dorsal (LD), lateral posterior (LP), pulvinar

What is the input to the lateral dorsal nucleus?

Hippocampus

Where does the lateral dorsal nucleus project?

Cingulate cortex

What is the main input to the lateral posterior nucleus?

Superior colliculus

Where does the lateral posterior nucleus project?

Superior parietal lobe

What does the pulvinar connect with?

Parietal, occipital, and temporal association cortices

What is the function of the lateral geniculate nucleus (LGN)?

Visual relay from retina to primary visual cortex

What is the function of the medial geniculate nucleus (MGN)?

Auditory relay from inferior colliculus to auditory cortex

What are symptoms of thalamic pain syndrome?

Severe pain, sensory loss, sleep disturbance, memory problems, visual issues

What is the internal capsule?

White matter pathway carrying fibers between thalamus and cortex

What fibers run in the anterior limb of the internal capsule?

Anterior and DM nucleus fibers to frontal lobe

What fibers run in the genu of the internal capsule?

VA and VL fibers to motor cortex

What fibers run in the posterior limb?

Corticospinal tract (anterior 2/3), VPL/VPM sensory fibers (posterior 1/3)

What fibers run in the retrolenticular part?

Optic radiations from LGN to visual cortex

What fibers run in the sublenticular part?

Auditory fibers from MGN to temporal lobe

What is the corona radiata?

Continuation of the internal capsule as fibers spread to cortex

Which nuclei appear in the anterior thalamic coronal slice?

Anterior nucleus, VA nucleus

Which nuclei appear in mid-thalamus coronal slice?

LD, VL, DM, CM, VPM, VPL

Which nuclei appear in posterior thalamus coronal slice?

LP, DM, CM, VPM, VPL, LGN, MGN, pulvinar