Diencephalon Flashcards
Components of diencephalon
Thalamus
Hypothalamus
Epithalamus (pineal gland, habenular nuclei and habenular commissure)
Subthalamus
(optic nerve and optic tracts)
Internal medullary lamina divides thalamus into what portions?
Anterior
Medial
Lateral
Divisions of lateral thalamus
Ventral and dorsal parts
What are the additional grey matter components associated with the thalamus?
Internal laminar nuclei (found within internal medullary lamina)
Interthalamic adhesion (mass intermedialis)
Lateral geniculate body
Medial geniculate body
Reticular nucleus
(External to external medullary lamina but intimately related to thalamus)
The sheet of white matter superior to thalamus?
Stratum zonale
Sheet of white matter lateral to thalamus?
External medullary lamina
What is found at the tip of the tail of the caudate nucleus?
Amygdala
Where is the hypothalamic sulcus?
Between thalamus and hypothalamus
What is the dorsal free margin of the thalamus, which is not related to the more medially located epithalamus?
Pulvinar
Of which part of the thalamus is the pulvinar?
Lateral dorsal thalamus
What is the principal function of the anterior thalamic nuclei?
Adjustment of mood in response to recent memory
Afferent connections of anterior thalamic nuclei
Mamillothalamic system (originally from fornix which is originating from hippocampal/parahippocampal portion of temporal lobe)
Where do most of the fibres from fornix which enter the hypothalamus terminate?
Mamillary body
Efferent connection of anterior thalamic nuclei
Cingulate gyrus
Papez circuit
Hippocampal-> fornix-> mamillary body-> anterior thalamic nucleus-> cingulate gyrus
Involved in recent memory
Which part of the Papez circuit is affected in Wernicke’s syndrome?
Mamillary bodies undergo degeneration or ischaemia
The function of the dorsal medial nucleus of the thalamus?
Adjust behaviour and psychological/physical state in response to mood
Afferent connections of the dorsal medial nucleus of the thalamus
All other internal thalamic nuclei
Basal ganglia
Lentiform nucleus
Hypothalamus
Efferent connections of the dorsal medial nucleus of thalamus?
Prefrontal cortex
Which thalamic nuclei are concerned with the limbic system?
Anterior thalamic
Dorsal medial nuclei
Important afferent connections of the intralaminar thalamic nuclei
Ascending reticular formation of the brainstem
All other thalamic nuclei
Ascending pain pathways:
Spinothalamic tract (which also activates reticular formation)
Trigeminothalamic tract
Efferent connections of intralaminar nuclei
The whole cerebral cortex
What is the function of intralaminar thalamic nuclei?
Cortical arousal
What is the largest intralaminar nucleus?
Centromedian nucleus
Connections of the centromedian nucleus
Significance?
All other thalamic nuclei
Motor cortex
Basal ganglia
Striatum
Motor activity can regulate levels of arousal.
Which part of the thalamus is affected in Wernicke’s syndrome?
Dorsal median nucleus
What are the three lateral dorsal tier thalamic nuclei from ventral to dorsal?
DPP
Lateral dorsal nucleus
Lateral posterior nucleus
Pulvinar
Connections of lateral dorsal nucleus
Similar to the anterior nucleus of thalamus, can be thought of posteriorly displaced anterior nucleus.
Mamillothalamic and thalamocingulate connections.
Connections of the lateral posterior nucleus
Two-way connection with superior parietal lobule and all other thalamic nuclei
Connections of pulvinar
Connections with all thalamic nuclei including strong connections with LGN and MGN
Two-way connections with sensory association cortices.
Brodman area- Primary occipital cortex
17
Brodman areas- Visual association cortex
19, 20
What is the difference between primary visual cortex and secondary/tertiary?
Initial sensory information is received in the primary cortex.
Subsequently, it is projected to the secondary area of visual association cortex where it is processed
Tertiary cortex compares new visual experience with previous information and tries to recognise it.
Function of primary sensory cortices
Receive information
Function of secondary sensory cortices?
Process information
Function of tertiary sensory cortices?
Compare to previous experiences to recognise object.
E.g. with written text
Primary receives image
Secondary identifies that it is English
Tertiary reads it
Secondary and tertiary sensory cortices together are known as?
Association areas
Consequence of pulvinar damage
Sensory aphasia
Unable to make sense of sensory information though the primary cortices are able to receive it.
What is the general arrangement of ventral tier nuclei
5 ventral tier nuclei
Two in front
Then three combined nuclei dorsally.
What is the most anterior ventral tier nucleus?
Ventral anterior nucleus
What is the second most anterior ventral tier nucleus?
Ventral lateral nucleus
Which of the ventral tier nuclei are concerned with motor function?
Ventral anterior nucleus
Ventral lateral nucleus
What are the three nuclei that make up the ventral posterior nucleus?
Ventral intermediate nucleus
Ventral posteromedial nucleus
Ventral posterolateral nucleus
Connections of the ventral anterior nucleus of the thalamus
Ventral anterior nucleus receives fibres from basal ganglia (specifically pallidothalamic fibres) and projects to the prefrontal cortex and premotor area.
Involved in planning motor movements
Connections of the ventral lateral nucleus?
Receives fibres from the corticopontocerebellar loops either via dentorubrothalamic pathway or dentothalamic pathway
Projects to SMA and 1o motor area
Again involved in planning and executing motor functions
Connections of ventroposterolateral nucleus
Receives medial lemniscus (dorsal columns)
Spinothalamic tract
Fibres ascend to the primary somatosensory cortex
Features of the thalamic syndrome
Thalamic injury, especially to sensory nuclei of VPN initially presents with contralateral hemianaesthesia
This may progress to intractable hemibody pain due to aberrant new intrathalamic connections.
Patients will often become depressed and may commit suicide.
Thalamic hand
Can be a consequence of damage to the motor component of the thalamus
The hand becomes pronated, and flexed, MCPJ flexed, ICPJ extended
The function of the ventral posteromedial nucleus of the thalamus?
Similar to ventral posterolateral but for head and neck
Receives afferents from the trigeminothalamic tract and tractus solitarius
Sends fibres to primary sensory cortex.
Function of VIM
The relay nucleus of the thalamus for the cerebellum, receiving input from the opposite cerebellum via the superior cerebellar peduncle. Output is to the primary motor cortex (Brodmann’s area 4) and premotor cortex
Connections of the reticular nucleus
Main regulator of thalamic activity
Receives information from the whole cerebral cortex
Receives information from ascending reticular formation
Sends fibres to all nuclei of the thalamus
3 basic functions of the hypothalamus
Part of the limbic system
Intimately related with the function of ANS
Endocrine function
AP extent of the hypothalamus
From midbrain to the optic chiasma
Sheet of grey matter
Swelling on the undersurface of the hypothalamus
Tuber cinereum
Mamillary bodies
What divides the hypothalamus into right and left areas?
The ventral part of the third ventricle
From which part of the parahippocampal formation do most of the fibres of the fornix originate?
Subiculum
Divisions of hypothalamus
Can be divided into medial and lateral side by an imaginary plane which is in line with the entry of the fornix and exit of the mamillothalamic tract
What fibres run from the frontal-orbital and septal area through the lateral hypothalamus into the brainstem
Medial forebrain bundle
What is the septal area of the brain?
Septal nuclei (medial olfactory area) structures below he rostrum of the corpus callosum, anterior to the lamina terminalis
.The septal nuclei are composed of medium-size neurons which are classified into medial, lateral, and posterior groups. The septal nuclei receive reciprocal connections from the olfactory bulb, hippocampus, amygdala, hypothalamus, midbrain, habenula, cingulate gyrus, and thalamus.
What are these hypothalamic nuclei?
Pre-optic nuclei
What is the function of the pre-optic nucleus?
Contains dimorphic nucleus which is thought to be involved in determining sexuality
Involved in the regulation of sexual function via the mediation of release of adenohypophyseal gonadotrophs through GnRH
What is this nucleus?
Lateral hypothalamic nucleus