Neuroscience 3 – Thalamus and Hypothalamus
Anil Chopra
1. Briefly describe the location and overall structure of the thalamus.
2. Give examples of how individual thalamic nuclei contribute to the functional
systems of the brain.
3. Explain the relationship between the intralaminar nuclei, reticular nuclei and the
reticular formation.
4. List the functions of the hypothalamus and outline the main pathways by which it
interacts with the endocrine system, autonomic system and parts of the brain
controlling mood and behaviour.
The Thalamus
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Situated in (and takes up most of the) diencephalon.
Divided in two (left and right) by third ventricle
Collection of individual nuclei with separate functions
Ipsilateral (same side) connections with forebrain
The thalamic nuclei are interconnected
 It is a relay centre between the cerebral cortex
and the rest of the central nervous system.
 Modulates and integrates information.
 It is involved in all functions except olfaction
(smell)
Left thalamus
Thalamic Nuclei
There are different types of nuclei in the thalamus. The specific nuclei are associated
with specific primary cortical areas in the cerebral hemispheres. They include:
NUCLEUS
Ventral lateral
Ventral anterior
CORTEX
Motor cortices (primary,
premotor, supplementary)
Ventral posterolateral
Somatosensory (body)
Ventral posteromedial
Somatosensory (head)
Lateral geniculate
Visual
Medial geniculate
Auditory
NB: primary cortical area is a small well-defined area of the cerebral cortex in which
damage leads to a defined deficit/paralysis
Association nuclei have more diffuse reciprocal connections with association cortex
(loosely defined cortex that is ill defined anatomically and that is difficult to assign
function to as damage does not always lead to deficit. Association areas help with
integration and so do the association nuclei of the thalamus
-
Anterior
Lateral Dorsal
Dorsomedial
Limbic system (cingulated and
prefrontal cortex)
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Lateral Posterior
Pulvinar
Association cortex at the junction of parietal,
temporal, occipital lobes and prefrontal cortex.
 The Intralaminar nuclei receive inputs from the Reticular Formation of the
brainstem and project diffusely to all cortical areas.
 The reticular nucleus also receives inputs from the reticular formation but
projects to the other thalamic nuclei only, regulating the flow of information
through these to the cortex.
 Thus the reticular formation, intralaminar and reticular nuclei form the Reticular
Activating System, which controls the level of arousal by modulating the level of
activity of the cerebral cortex.
Thalamic Syndrome (Dejerine-Roussy) is a rare neurological disorder in which the
body becomes hypersensitive to pain as a result of damage to the thalamus (usually as
a result of stroke or infarct). It can also cause a great deal of emotional disturbance.
Hypothalamus
 Situtaed just inferior to the
thalamus in the diencephalon.
 Also divided into left and right
by the third ventricle.
 Each side has a collection of
individual nuclei with separate
functions and ipsilateral
connections with forebrain
structures.
 Its main function is
homeostasis by endocrine
association with the pituitary
gland
 Regulates autonomic nervous
system via connections with the brainstem and spinal cord.
 Also has an effect on behaviour via connections with forebrain.
It is associated with the following parts of the forebrain:
• Olfactory system
• Limbic system - hippocampus, amygdala, cingulate cortex, septal nuclei
This allows it to control behaviour by acting as an interface between nuclei
controlling systems. It works to maintain drives, motivations via pleasure/ pain
centres
It is associated with behaviour in the following areas:
• Eating and drinking
• Expression of emotion
• Sexual behaviour
• Circadian rhythm
• Memory
Hypothalamic Tumour
Initial Symptoms:
- Polydipsia (drinking a lot of water)
- Polyuria (urinating a lot)
- Absence of periods
Symptoms that may develop later:
- labile emotions, rage
- inappropriate sexual behaviour
- memory lapses
- temperature fluctuation
- thyroid, adrenal cortex, gonadal function decreases
- hyperphagia (eating a lot).