Microscopy of the diencephalon András Csillag In collaboration with Prof. Á. Dobolyi and Dr. V. Vereczki Semmelweis University, Department of Anatomy, Histology and Embryology

The position of the diencephalon in the brain

Parts of the diencephalon Thalamus Epithalamus Pineal body Habenula Trigonum habenulae Habenular nuclei Stria medullaris Habenular commissure Metathalamus Medial geniculate body Lateral geniculate body Subthalamus Subthalamic nucleus Zona incerta H fields of Forel Hypothalamus

Midsagittal (A) and frontal (B) sections of midbrain

Thalamic subdivisions of human brain Williams et al., (1989) Gray’s Anatomy, Churchill Livingstone

Functional groups of thalamic nuclei Mammalian system Nucl. ventralis post. VPL/VPM SENSORY THALAMUS MOTOR THALAMUS Ventral tier nuclei (VA/VL) Anterior nuclei VISCERAL AND LIMBIC THALAMUS Intralaminar nuclei Midline nuclei Mediodorsal nucleus

Nuclear groups and nuclei of the thalamus

Frontal sections of the thalamus Anterior section Middle section

Functional classification of thalamic nuclei Specific nuclei: specific input, project to specific part of the cortex - sensory relay nuclei: VPL, VPM, CGL, CGM - motor relay nuclei: VA, VL - limbic relay nuclei: AV, AD, AM Associate nuclei: cortical input, project to associate areas of the cortex MD, LD, LP, pulvinar Non-specific nuclei: ascending input, diffuse projection to the cortex midline and intralaminar nuclei Nuclei not projecting to the cerebral cortex n. reticularis thalami, n. parafascicularis, n. subparafascicularis

Cortical projections of (specific and associate) thalamic nuclei mediosagittal view lateral view

Specific sensory relay nuclei

The VPL relays sensory inputs from the body to the cerebral cortex

The VPM relays sensory inputs from the head to the cerebral cortex

Relay of gustatory inputs to the cortex takes place in the VPMpc

Somatotopy in the VPM/VPL

Specific motor relay nuclei

Afferent and efferent projections of the motor relay nuclei in the ventral column of the lateral nuclear group (‚ventral tier’ nuclei) Specific thalamic motor relay nuclei: Ventral anterior nucleus (VA) Afferents (inputs): basal ganglia (pallidum) Efferents (projections): premotor and supplementary motor cortex Ventral lateral nucleus (VL) Afferents (inputs): cerebellum (dentate nucleus) Efferents (projections): primary motor cortex (precentral gyrus )

Neuronal circuit of information relay in the specific thalamic nuclei

State-dependent modes of relay cell function

Midline and intralaminar nuclei of the thalamus

The IMMC Complex 1. Midline thalamic nuclei: Paraventricular Parataenial Intermediodorsal Rhomboid Reuniens 2. Mediodorsal nucleus 3. Intralaminar nuclei: Rostral group Central medial Paracentral Central lateral Caudal group Centre médian Parafascicular

Midline thalamic group: paraventricular nucleus Input from preoptic area Output to medial orbitofrontal cortex Output to dorsomedial hypothalamus (DMH) Input from (output to ?) midbrain periaqueductal gray (PAG)

Mediodorsal thalamic nucleus Output to prefrontal cortex and anterior cingulate cortex Output to amygdala Reciprocal (?) connections with lateral hypothalamus and PAG

Intralaminar thalamic group Output to non-limbic (visceral, sensory and motor) cortices Output to (mainly) dorsal striatum Output to hypothalamus ? Output to reticular thalamic nuclei Nissl-stained monkey brain at the level of the caudal intralaminar nuclei

Major inputs and projections of midline and intralaminar thalamic nuclei Spino-reticulo-thalamic tract – part of the „ascending reticular activating system”, a regulator of cortical alertness bal alsók: O:\ A_PM\Előadások-ppt\Human brain-040611\rajz1-09Sept-2valtA.jpg + rajz1-09Sept-2valtB.jpg (mérete: 6,35x6,63 cm; pozíciója: 1,2; 10,83 cm) középen: O:\A_PM\Előadások-ppt\090910-September\Kandel_page342-5valtozat1-ures.jpg + Kandel_page342-5valtozat2-piros.jpg (méret: 17,53x7,12 cm; pozíció: 9,1; 1,47 cm) jobb felső: O:\A_PM\Előadások-ppt\Human brain-040611\rajz2-20101005-sarga.jpg + rajz2-20101005-pirossal.jpg (méret: 6,19x6,6 cm; pozíció: 17,48; 1,74) jobb középső: O:\A_PM\Előadások-ppt\_Fájdalom, 2010\Duvernoy_page23.jpg jobb alsó: Insula.jpg innen másolva: O:\A_PM\Előadások-ppt\2011,insula (Fájdalom,Debrecen)\Fájdalom-Debrecen,2011.ppt\27. dia

Cortical efferents of thalamic nuclei CGL LD PULV. LP VPL+VPM VL VA DM CGM

Thalamic reticular nucleus: a regulator of the relay function of specific thalamic nuclei

GABAergic inhibitory neurons in the thalamus

The hypothalamus Thalamus Epithalamus Metathalamus Subthalamus Pineal body Habenula Trigonum habenulae Habenular nuclei Stria medullaris Habenular commissure Metathalamus Medial geniculate body Lateral geniculate body Subthalamus Subthalamic nucleus Zona incerta H fields of Forel Hypothalamus

Essential differences between the structure and functions of the thalamus and hypothalamus Thalamus: - well delineated nuclei - relay and modulation of cortical inputs Hypothalamus: The neurons with different functions are intermingled, not clearly separated Homeostatic regulatory functions do not require cortical processing

Antero-posterior regions of the hypothalamus

Medio-lateral zones of the hypothalamus

Nuclei in the medial zone of the hypothalamus

Anterior hypothalamic region

Tuberal and posterior hypothalamic regions Tuberal hypothalamic region Posterior hypothalamic region

Neuronal inputs to the hypothalamus

Circumventricular organs – humoral inputs

Extrahypothalamic projections of hypothalamic nuclei

Hypothalamo-spinal tract and other descending pathways regulating vegetative functions

Regulatory functions of hypothalamic nuclei Vegetative regulations Neuroendocrine regulations Salt and water balance Food intake and body weight Temperature Circadian rhythms Sleep Reproduction

Neural elements of homeostatic regulations NTS: nucleus of the solitary tract, PBN: parabrachial nucleus, RF: reticular formation, DMX: dorsal motor vagus nucleus, ILN: intermediolateral column (nucleus) of the spinal cord

Hypothalamic centers that control food intake and body weight

Principle of creating circadian (daily) rhythms

Circadial regulation of neural functions PACEMAKER: SUPRACHIASMATIC NUCLEUS (SCN)

Neuronal inputs and outputs of the suprachiasmatic nucleus

5. control of circadian rhytms: retinohypothalamic tract Medial zone Suprachiasmaticus nucleus (VIP) : retinohypothalamic tract of rat (Scale: 100 µm. OX= optic chiasm;SCH=suprachiasmatic nucleus)

SUBTHALAMUS - Ventral from thalamus - Caudal and lateral from hypothalamus - Prosomere 3 + Peduncular hypo- thalamus (basal part) Main parts: Subthalamic nucleus (Luys) Zona incerta Fields of Forel

EPITHALAMUS Habenular nuclei Septohabenular pathway (stria medullaris thalami) Retroflex fascicle (fasciculus retroflexus) – habenulo-interpeduncular pathway Retroflex fascicle – border between prosomers 1 and 2 Part of the limbic system, From stress evasion to value-based decision making, Connections with the basal ganglia and the serotonergic system of brainstem (raphe nuclei)