3. Parts Of The Diencephalon
• Thalamus
• Hypothalamus
• Epithalamus
• Pineal and
habenular
complex
• Subthalamus
4. Ventral thalamus
Dorsal thalamus
Anatomically and functionally, four regions can be distinguished in the
thalamus: anterior, posterior, medial, and lateral, partially separated from
each other by white matter laminae that are visible to the naked eye
Anterior Posterior
Divisions of
thalamus
5. Thalamic Nuclei
Anatomically and functionally, four regions can be distinguished in
the thalamus: anterior, posterior, medial, and lateral nuclei
The intralaminar nuclei and the reticular nucleus of the thalamus
7. The thalamus is composed of many nuclei, which have motor, sensory, and limbic
connections.
Some nuclei are nonspecific in nature.
8. From a diagnostic standpoint, the complex thalamic
anatomy can be divided into four main regions
Non-specific thalamic nuclei
• The midline, intralaminar, reticular, and some areas of the ventral
anterior nuclei
• Mediate general cortical alerting responses
• Receive strong projections from the midbrain reticular formation,
hypothalamus and the spinothalamic tract as well as from other
sensory pathways.
• Lesions that involve these structures bilaterally cause impairment
of alertness
9. From a diagnostic standpoint, the complex thalamic
anatomy can be divided into four main regions
The medial (dorsomedial) and anterior thalamic nuclear groups
• Play an important role in memory and emotions
• They are connected with the hypothalamus, the “limbic lobe”
and the frontal lobe
• The dorsomedial nucleus mediates olfaction, emotions, the
secondary affect of pain, the sleep-wake cycle, and executive
functions
• Lesions are more consistently associated with memory and
executive function loss
10. From a diagnostic standpoint, the complex thalamic
anatomy can be divided into four main regions
The ventral lateral and basal nuclear groups
• Are concerned with the processing of sensory information and
relaying it to the cortex
• Ventral posterior nuclear group
• Medial geniculate body and Lateral geniculate body
• Also concerned with sensori-motor control
• Ventro-lateral nucleus and Ventral anterior nucleus
11. From a diagnostic standpoint, the complex thalamic
anatomy can be divided into four main regions
The dorsolateral and posterior nuclear groups, particularly the
pulvinar
• This area is much better developed in humans
• Seem to modulate occipito-temporo-parietal cortical attention,
using an object-based frame of reference
• It facilitates visual attention and the cortical attention needed
• Language related sensory tasks in the left hemisphere
• Visuo-spatial tasks in the right hemisphere
13. Thalamic Integrations
THALAMUS
SENSORY INPUT
VICERAL INPUT
MOTOR
COORDINATION
CONCIOUSNESS
AFFECT
SLEEP WAKE
CYCLE
CORTEX
LIMBIC
SYSTEM
Characteristically, thalamic connections are reciprocal, that is, the target
of the axonal projection of any given thalamic nucleus sends back fibers to
that nucleus
15. Disturbances in Thalamic Lesions
• Disturbances of Alertness and Sleep
• Autonomic Disturbances
• Disturbances of Mood and Affect
• Memory Disturbances
• Sensory Disturbances: Positive and Negative symptoms
• Motor and Postural Disturbances
• Disturbances of Ocular Motility
• Disturbances of Complex Sensori-motor Functions
• Disturbances of Executive Function
16. Thalamic nuclei
Anterior nuclear group
• Mammillary bodies and
Hippocampus
• Anterior nuclei and
dorsomedial nuclei
• Cingulate gyrus
• Short term memory
• Loss of Constructing a
balance between instinctive
and volitional behavior
• Executive function
• Wernicke- Korsakoff's
syndrome
17. Thalamic nuclei
Dorso-medial nuclei
• Mediates
• Olfaction
• Emotions
• The secondary affect of
pain
• The sleep-wake cycle
• Executive functions
• Connected with
• Hypothalamus
• The “limbic lobe”
(Amygdala, medial
temporal region, insula)
• The frontal lobe.
LESIONS AT THIS NUCLEI
Sleep disturbances
Emotional liability or
Apathy
Executive dysfunction
18. Thalamic nuclei
Ventral nuclear group (VAG)
• Pallidum, Substantia nigra,
Dorsal medial thalamic
nucleus
• Ventral anterior group
(VA,VI VL)
• Orbitofrontal cortex, Intra-
laminar thalamic nuclei,
Dorsal medial thalamic
nucleus
• Hyperkinetic movement ds.
• Ataxia
• Problem of recruiting
response: Motor aphasia
• Play a role in voluntary
attention
• Attention deficit
19. Thalamic nuclei:
Ventral nuclear group (VPG)
• Spinothalamic, ML,
trigeminal nuclei, Optic T.
• Ventral posterior group
(VPL,VPM)
• Primary and secondary
sensory cortex; Occiptal C.
• Contralateral hemi-sensory
loss
• Contralateral Sensory ataxia
• Gustatory affection
• Visual field defects
20. Thalamic nuclei
Posterior nuclear group 1:
Ventral group
• Bilateral receptors of noxious
stimuli; brachium of the
inferior colliculus;
Contralateral visual field (optic
tract)
• Posterior thalamic zone; MJB
and LGB.
• Other thalamic nuclei;
Transverse temporal gyrus of
Heschl; Calcarine cortex
• Disturbances of Ocular
Motility
• Visual field defects and visual
inattention
• Problem of recruiting auditory
response: Sensory aphasia
21. Thalamic nuclei
Posterior nuclear 2:
Lateral dorsal group
• MJB,LJB, VL nuclei
• Lateral nuclear group (LDP
and pulvinar)
• Auditory, occipital and
temporal (Wernicke area)
cortices
• Visual spatial attention (non
dominant)
• Language related attention
(dominant): Sensory aphasia
• Occulo-motor and gaze palsy
22. Thalamic nuclei: Non specific nuclei
• The midline, intra-laminar,
reticular, and some areas of
the ventral anterior nuclei
• Mediate general cortical
alerting responses.
• Involved in alertness and
normal sleep wake cycle
• Affect and emotions
• Loss of consciousness…….
Afferents from midbrain reticular
formation, hypothalamus and the
spino-thalamic tract as well as from
other sensory pathways.
Efferents to midbrain and to the
specific thalamic nuclei
24. Example: Localization on vascular territory
Stroke at this territory
Transient LOC, mutism, sleepiness
Memory loss, behavioral changes
Contralateral ataxia, action tremor or HMD
25. Tips On Thalamic Lesions
The smallness of the thalamus
• Several of the nuclei and even several of the functional regions
outlined above are usually affected simultaneously by discrete
lesions
• Because arteriolar vascular territories cross the nuclear
boundaries, as a rule ischemic disease affects several nuclei,
often partially.
• In addition, many lesions are not restricted to the thalamus,
but involve neighboring areas of the brain as well.
26. Tips On Thalamic Lesions
The location and nature of thalamic lesions
• Except for sensory deficits, unilateral thalamic lesions result in
transient deficits.
• By contrast, bilateral lesions or unilateral lesionswhich press
against the contralateral thalamus or impinge on the midbrain:
• May render the patient comatose or akinetic and mute.
27. Tips On Thalamic Lesions
Timing has a particular impact on the clinical expression of thalamus
• As the effects of an acute lesion recede
• Neglect may disappear
• Inability to walk may yield to mild ataxia
• Hemisensory loss diminishes.
• Other findings, however, particularly the so-called positive
symptoms usually become more pronounced within a few weeks
after the injury
• Tremor and pain
28. Tips on Hypothalamic Lesions
• Since these structures are small, several portions may be involved
simultaneously.
• Lesions that progress rapidly cause a more florid clinical
symptomatology than those that proceed slowly.
• Unilateral lesions are seldom symptomatic.
• The changes of hypothalamic function with age are reflected in
the disparity of the syndromes caused in different age-groups by
similarly located lesions: Gigantism vs acromegaly
31. Hypothalamic lesions
Anterior Hypothalamus
• Hyperthermia
• Loss of parasympathetic
act.
• Insomnia, loss of cycle
• Neurogenic ulcer and
emesis
• Hyperdypsia
• Obesity
• Rage, blunt expression
Posterior Hypothalamus
• Hypothermia and
pokilothermia
• Loss of sympathetic activity
• Hypersomnia, narcolepsy
• Adypsia
• Weight loss
• Fear and horror
• Apathy
