Thalamus - Sufaro Flashcards
What are the functions of the thalamus?
- Processes all sensory information, (with the
exception of olfactory info) prior to relaying
to cerebral cortex - Regulates the execution of motor programs
- Controls the level of cortical excitability
- Influences motivational & emotional
responses
Receives input from different places (largest input from cerebral cortex) and integrates through interconnections between the nuclei and sends primarily to cerebral cortex but also to basal ganglia and hypothalamus
Diffuse projections for things like language
What are the functions of the anterior part of the thalamus?
•Function : associated with that of
the limbic system and is
concerned with emotional tone
and the mechanisms of recent
memory
•Contains the anterior thalamic
nucleus
•hypothalamic input from mamillothalamic tract
•It receives hippocampal input via
the fornix (hippocampus).
•It projects to the cingulate gyrus.
What are the functions of the lateral part of the thalamus (ventral anterior and ventral lateral nuclei)?
•Motor relay nuclei associated with somatic
motor system
Ventral anterior nucleus connects to the premotor cortex
Ventral lateral nucleus connects to the motor cortex
Ventral posterolateral nucleus connects to the sensory cortex. Proprioceptive information from the face enters here.
Dorsal tier/ Pulvinar processes complex visual and language input, projects to parietal temporal and occipital cortices
What are the functions of the medial part of the thalamus?
•Contains the large Mediodorsal
nucleus and several smaller nuclei
•Function:
Cognitive
function, memory.
Decision making
Connected to prefrontal cortex of frontal lobe and thalamic nuclei
It receives input from the
•amygdaloid nucleus
•temporal neocortex
•substantia nigra
In alcohol abuse gets impaired and atrophied (with cerebellum)
What is the effect of injury to the mediodorsal/dorsomedial nucleus of the thalamus?
Wernicke- Korsakoff syndrome
memory loss
Atrophy of cerebellum
Creates drunk effect even when not drunk, though caused by excess drinking
What are the functions of the intralaminar nuclei in the thalamus?
•A groups of nuclei embedded within
the internal medullary lamina
•input from the brainstem reticular
formation
•Project diffusely to the entire
neocortex.
•Regulate levels of activity of cerebral cortex
Includes ARAS (Ascending Reticular Activating System- one center in pons and one here) Determines how much info rises from periphery to cortex (when sleeping, blocks stimuli, when alert, passes through)
What is the Lateral Geniculate Body (LGB) and what does it do?
- It is a swelling on the undersurface of the pulvinar of the thalamus
- It is a visual relay nucleus.
- It receives retinal input via the optic tract.
• Each LGB receives information form the opposite field of vision
• It projects to the primary visual cortex in occipital lobe (area 17, the lingual gyrus and the cuneus and 18 and 19) via the optic radiation.
Exception: Meyer’s loop: projections into temporal lobe (so damage here also causes visual field defects)
What is the Medial Geniculate Body and what does it do?
- It is a swelling on the posterior surface of the thalamus beneath the pulvinar
- It is an auditory relay nucleus .
- It receives auditory input via the brachium of the inferior colliculus that receives the termination of the fibers of the lateral lemniscus between the medulla and the pons
Input from vestibular (inner ear) -cochlear (hearing) nerve
Information bifurcates in the cochlear nucleus and part goes ipsilateral and part contralateral up lateral lemniscus and brachium of inferior collicullus –> lateral discrimination
Cortical damae on one side does not cause deafness because of this decusation
- It receives auditory information from both ears but predominantly from the opposite ear
- It projects to the primary auditory cortex (areas 41 and 42) via the auditory radiation.
What is the blood supply of the thalamus?
Posterior Communicating Artery and Posterior Cerebral Artery
Gives rise ot anterior thalamoperforating arteries
Supply Circle of Willis
Prone to atherosclerosis
Anteiror choroidal artery
Supplies the LGB and MGB on the way to lateral ventricles
From the internal cartoid artery
What is Thalamic syndrome (Dejerine and Roussy) and what are its signs?
Injury resembles a cortical lesion, thalamic stroke
Is usually caused by occlusion of a posterior thalamoperforating artery! Can cause even a small bleed.
Classic signs are:
1. Contralateral hemiparesis
2. Contralateral hemianesthesia
3. Spontaneous, agonizing, and burning pain
(hyperpathia, Thalamic Pain Syndrome, Dejerine & Roussy syn.)
Sensory deficit on one side
Lower threshold of pain
