Diencephalon: Structure and Function Flashcards
Location of the Diencephalon
Embryologically between the telencephalon and mesencephalon
Between cerebral cortex and brainstem
Medial to internal capsule
Divided in the midline by the third ventricle
Diencephalic Subdivisions
Epithalamus Dorsal thalamus Ventral thalamus Subthalamus Hypothalamus
Epithalamus consists of:
Habenula, Pineal Gland, Posterior Commissure
Dorsal Thalamus (or Thalamus) consists of:
Thalamic nuclei, External Medullary Lamina, Internal Medullary Lamina
Ventral Thalamus consists of:
Reticular Nucleus of the Thalamus
Ventral Lateral Geniculate Nucleus (vLGN)
Subthalamus consists of:
Zona Incerta Subthalamic Nucleus (of Luys)
Hypothalamus consists of:
Hypothalamic nuclei, Infundibulum, Hypophysis (pituitary gland), Hypophyseal portal system
Blood Supply of the Thalamus
Anterior communicating artery Posterior communicating artery ACA PCA Internal Carotid Artery
What are some functions of the thalamus??
“Gateway to the cortex”
- Relays all sensory information to the cerebral cortex
- Relays information about motor activities to the cerebral cortex
- Integrates sensory information from different modalities and projects to association cortex
- Relays emotional and affective information to the cortex
- Part of “Papez Circuit” of the limbic system, projects to limbic cortex
- Intimately involved in the control of alertness, arousal and sleep
- Under direct cortical feedback and control: reciprocal connections between the thalamus and the cortex
Afferent Input, Efferent Output and Function of Anterior Nuclear Group
Afferent: Mammillary Body
Efferent: Cingulate gyrus
Functions: Limbic
Afferent Input, Efferent Output and Function of Ventral Anterior
Afferent: Globus Pallidus
Efferent: Premotor Cortex (area 6)
Functions: Motor
Afferent Input, Efferent Output and Function of Ventral Lateral
Afferent: Dentate nucleus of cerebellum
Efferent: Motor and premotor (areas 4 and 6)
Functions: Motor
Afferent Input, Efferent Output and Function of Ventral Posterior Lateral
Afferent: Dorsal column-medial lemniscus and spinothalamic
Efferent: Somatosensory cortex (areas 3, 1, 2)
Functions: Somatic sensation (body)
Afferent Input, Efferent Output and Function of Ventral Posterior Medial
Afferent: Sensory nuclei of trigeminal nerve
Efferent: Somatosensory cortex (areas 3, 1, 2)
Functions: Somatic sensation (face)
Afferent Input, Efferent Output and Function of Lateral geniculate
Afferent: Retinal Ganglion Cells
Efferent: Primary Visual Cortex (area 17)
Function: Vision
Afferent Input, Efferent Output and Function of Medial geniculate
Afferent: Inferior colliculus
Efferent: Primary auditory cortex (areas 41, 42)
Function: Audition
Afferent Input, Efferent Output and Function of Lateral Dorsal
Afferent: Cingulate gyrus
Efferent: Cingulate gyrus
Function: Emotional expression
Afferent Input, Efferent Output and Function of Lateral Posterior
Afferent: Parietal cortex
Efferent: Parietal cortex
Function: Emotional expression
Afferent Input, Efferent Output and Function of Pulvinar
Afferent: Superior Colliculus, Parietal, Occipital and Temporal lobes
Efferent: Parietal, occipital and temporal lobes (POT)
Function: Integration of sensory information
Afferent Input, Efferent Output and Function of Medial Dorsal
Afferent: Amygdaloid nuclear complex, olfactory, hypothalamus
Efferent: Prefrontal Cortex
Function: Limbic
Afferent Input, Efferent Output and Function of Midline Nuclei
Afferent: Reticular formation and hypothalamus
Efferent: Basal forebrain
Functions: Limbic
Afferent Input, Efferent Output and Function of Intralaminar nuclei: Centro-median, Centro-lateral and Parafascicularis
Afferent: Reticular formation, spinothalamic tract, globus pallidus, and cortical areas
Efferent: Basal ganglia and wide areas of cortex
Function: Role in pain, sleep and wakefulness
Afferent Input, Efferent Output and Function of Reticular nucleus
Afferent: Cortex, thalamus, brain stem reticular formation
Efferent: Thalamic nuclei
Function: Modulation of thalamic activity
What is Thalamic Syndrome?
Caused by vascular lesion/tumor (rare)
Usually involves damage to the lateral group of thalamic nuclei (VPL)
Initially: contralateral hemianalgesia
Soon: painful sensations appear with noxious stimuli
Later: pain is provoked by pressure, touch and vibration
In time: state of spontaneous, constant or paroxysmal pain is evoked on the affected side (contralateral to the lesion) without any external stimulus (Dysesthesia)
Threshold for pain, temp and tactile sensate is usually raised on the affected side – but once the threshold is reached, pain has a strong emotional overtone to it.
