DPT 746 Lecture 19 Thalamus

What is the largest nuclear mass in the entire nervous system?

Thalamus

Shape of the thalamus

Egg-shaped

Relative location of the thalami in the brain

Lie at the center of the brain

Describe the orientation of the two thalami in relation to another. What structure connects them?

Thalami face each other medially, connected via interthalamic adhesion

Alternative name for interthalamic adhesion

Massa intermedia

Does the thalamus have one unitary function?

No, connections are too diverse

With hypothalamus, thalami form the lateral wall of this space

Third ventricle

Areas of the thalamus (4, including thalamus)

Epithalamus
Thalamus
Subthalamus
Hypothalamus

Relative location of the epithalamus in relation to other areas of the thalamus (2 directional terms)

Most caudal
Most dorsal

Components of the epithalamus (3)

Pineal gland
Habenula
Stria medullaris

What is the meaning behind the name "pineal" gland?

Pine cone shaped

Functions of the pineal gland (3)

Releases melatonin (endocrine glad)
Controls sleep/wake cycles via circadian rhythm
Regulates onset of puberty

During what conditions will the pineal gland create melatonin?

If the eye senses a dark environment

Habenula is connected to what structure? Function?

Connected to limbic system
Mediates olfactory stimuli and feeding behaviors

Describe the stria medullaris

Fascicle of nerve fibers from habenular nuclei w limbic connections

What is the name for the internal organization of the thalamus?

Internal medullary laminae

When viewed from above, the internal medullary laminae forms what shape?

Y shaped when viewed from above

What's contained in the internal medullary laminae?

Nerve fibers (white matter)

Internal medullary laminae divides thalamus into these large cell groups (3)

Anterior
Medial
Lateral

Structures embedded within internal medullary laminae

Intralaminar nuclei

Which nuclear group has the medial and lateral geniculate laminae within it?

Lateral nuclear group

All nuclei in thalamus have what sort of connections to cerebral cortex?

Reciprocal excitatory connections (except for inhibitory reticular nucleus)

Functional categories of thalamic nuclei (3)

Specific nuclei (relay nuclei)
Association nuclei
Non-specific nuclei

List all of the specific nuclei (6)

Anterior nucleus
Ventral anterior (VA)
Ventral lateral (VL)
Ventral posterior (VP)
Medial geniculate
Lateral geniculate

List all of the association nuclei (3)

Lateral dorsal
Dorsomedial
Posterior lateral and pulvinar

List all of the non-specific nuclei (2)

Intralaminar
Reticular

What are specific nuclei connected to?

Connected to specific motor or sensory areas of cerebral cortex

Anterior nucleus is part of what system? Function?

Part of limbic system
Function: Memory, emotional aspect of behavior

Anterior nucleus afferents and efferents

Afferents: Mammillary body (mammillothalamic tract)
Efferents: Cingulate cortex

Ventral anterior nucleus (VA) afferents and efferents

Afferents: Globus pallidus, substantia nigra
Efferents: Prefrontal cortex, motor regions (premotor, motor cortices)

Portions of the ventral lateral nucleus (VL) (just names) (2)

Anterior part
Posterior part

Anterior part of ventral lateral nucleus (VL) afferents and efferents.

Afferent: Globus pallidus
Efferent: Supplementary motor area

Function of anterior part of ventral lateral nucleus (VL)

Planning and initiation of movements

Posterior part of ventral lateral nucleus (VL) afferents and efferents

Afferent: Dentate nucleus (contralateral superior cerebellar peduncle)
Efferent: Premotor cortex, primary motor cortex

Ventral posterior nucleus (VP) afferents and efferents

Afferent: Medial, spinal and trigeminal lemnisci
Efferent: Somatosensory cortex

Somatotopic organization of ventral posterior nucleus (VP) includes these regions (2)

Ventral posteromedial nucleus (VPM)
Ventral posterolateral nucleus (VPL)

VPM receives sensory info from what area of body? VPL?

VPM: Face and head
VPL: Trunk and limbs

Modality segregation for VPM and VPL (3 nuclei groups in thalamus have what function for VPL and VPM?)

Anterior: Proprioception
Middle: Tactile
Posterior: Nociception

Function of medial geniculate nucleus

Auditory pathway

Medial geniculate nucleus afferents and efferents

Afferents: Inferior brachium from inferior colliculus
Efferents: Primary auditory cortex (superior temporal gyrus)

Function of lateral geniculate nucleus

Vision

Lateral geniculate nucleus afferents and efferents

Afferents: Retinal inputs from both eyes via optic tract
Efferents: Primary visual cortex (occipital lobe)

Function of lateral dorsal nucleus

Involved in functions related to memory

Lateral dorsal nucleus afferents and efferents

Afferent: Hippocampus
Efferent: Cingulate cortex

Function of dorsomedial nucleus

Has functions related to cognition, judgement and mood

Dorsomedial nucleus afferents and efferents

Afferents: Prefrontal cortex, olfactory, limbic systems
Efferents: Prefrontal cortex

Function of posterior lateral nucleus + pulvinar

Draws attention to objects in peripheral field of vision

Posterior lateral nucleus + pulvinar afferents and efferents

Afferents: Superior colliculus, primary visual, auditory and somatosensory cortex
Efferents: Visual association cortex, parietal association cortex

What structure houses the intralaminar nuclei of thalamus?

Internal medullary lamina of white matter

Functions of intralaminar nuclei (4)

Activation of cerebral cortex
Arousal
Cognition
Relay of nociceptive info to cerebral cortex

Effect of lesions to intralaminar nuclei (2)

Reduce perception of pain
Reduce level of consciousness

Describe the shape and orientation of thalamic reticular nucleus

Shield-like shaped nucleus around front and lateral side of thalamus (looks like a sock)

What separates thalamic reticular nucleus from thalamus?

External medullary laminae

Thalamic reticular nucleus afferents and efferents

Afferents: Thalamus and cortex
Efferents: Thalamus (specific nuclei) - Modulates rate of discharge to cortex

Types of fibers that are afferents and efferents to thalamic reticular nucleus

Thalamocortical and corticothalamic

Describe the thalamic peduncles

Fibers going into thalamus are arranged into bundles that travel together

Describe the impact of thalamic lesions (generally). What typically causes thalamic lesions?

Relatively small lesions can cause a large collection of deficits.
Damage usually d/t vascular accident

Alternative name for thalamic pain syndrome

Central pain syndrome

Lesions to these areas can cause central pain syndrome (2)

Ventral posterior nucleus (VP)
Anywhere along pain-conduction pathway

Common causes of thalamic pain syndrome

Injury or stoke, typically vascular accident of one small branch of PCA

Typical time frame for onset of thalamic pain syndrome

Can vary from days to weeks, months or even more than a year after lesion

Are thoracic pain syndrome symptoms ipsi or contralateral to lesion?

All contralateral to lesion

S/s of thalamic pain syndrome (4)

Thalamic pain
Hemianesthesia
Sensory ataxia
Hemiparesis

Pain distribution of thalamic pain syndrome

Pain can be limited to specific areas (hand and feet) or involve many portions of contralateral half of body

Pain description for thalamic pain syndrome (5 sensations)

Burning
Stabbing
Lacerating
Ache
Pins and needles

Provoking factors for thalamic pain syndrome? Time of day that the pain is worst?

Can be affected by stress, touch, temp change
Can fluctuate during day
Rest and distraction may lessen symptoms

How does thalamic pain syndrome distort pain sensations?

Stimuli that don't cause pain may be perceived abnormally
Intensity may be disorted

Can thalamic pain syndrome be relieved via pain killing medication?

No, usually resistant to pain killers