DiencephalonDiencephalon

Functional anatomyFunctional anatomy

and and

histologyhistology

Basic termsBasic terms

Diencephalon: the brain part between the forebrain Diencephalon: the brain part between the forebrain and midbrain (Zwischenhirn).and midbrain (Zwischenhirn).

Cavity: third ventricle.Cavity: third ventricle.

Dorsal diencephalon: thalamus, epithalamus, Dorsal diencephalon: thalamus, epithalamus, metathalamus.metathalamus.

Ventral diencephalon: hypothalamus.Ventral diencephalon: hypothalamus.

Subthalamus: brain area connecting the midbrain Subthalamus: brain area connecting the midbrain and the diencephalon.and the diencephalon.

Epithalamus: corpus pineale, habenula, commissura Epithalamus: corpus pineale, habenula, commissura posterior, stria medullaris.posterior, stria medullaris.

Metathalamus: corpus geniculatum mediale (CGM), Metathalamus: corpus geniculatum mediale (CGM), corpus geniculatum laterale (CGL). corpus geniculatum laterale (CGL).

THE MEDIAL SIDE OF THE DIENCEPHALON: GREEN LINE SHOWS THE TENIA THE MEDIAL SIDE OF THE DIENCEPHALON: GREEN LINE SHOWS THE TENIA THALAMITHALAMI

Vena interna cerebriVena interna cerebri

66

F: fornixF: fornixME: mesencephalonME: mesencephalonP: ponsP: ponsMY: medullaMY: medullaCE: cerebellumCE: cerebellum1: corpus callosum1: corpus callosum2: septum pellucidum2: septum pellucidum3: thalamus3: thalamus4: hypothalamus4: hypothalamus5: hypophysis5: hypophysisArrows: tentorium cerebelliArrows: tentorium cerebelli

Frontal plane section cuttingFrontal plane section cuttingthrough the anterior thalamusthrough the anterior thalamus(medial, ventral nuclei,(medial, ventral nuclei,internal capsule)internal capsule)

Horizontal plane section through the dorsal thalamusHorizontal plane section through the dorsal thalamus

PULVINAR THALAMI, PULVINAR THALAMI, EPITHALAMUSEPITHALAMUS

Post. commissure

Pineal gland

pulvinar

Pul

Pul Pul

Topography Topography

Laterally: capsula internaLaterally: capsula interna

Dorsally: nucleus caudatus, cella media Dorsally: nucleus caudatus, cella media (ventriculus lateralis)(ventriculus lateralis)

Medially: ventriculus tertiusMedially: ventriculus tertius

Ventrally: subthalamus, substantia nigraVentrally: subthalamus, substantia nigra

Subthalamus: nucleus subthalamicus, ansa Subthalamus: nucleus subthalamicus, ansa lenticularis, fasciculus thalamicus, fasciculus lenticularis, fasciculus thalamicus, fasciculus lenticularislenticularis

Posterior: tectum mesencephaliPosterior: tectum mesencephali

Anterior: nucleus caudatus, capsula interna, Anterior: nucleus caudatus, capsula interna, lamina terminalislamina terminalis

Thalamus, nuclei basales (nucl. caudatus, nucl. lentiformis), capsula internaas seen on a horizontal brain section. The claustrum and the insula are also visible, with the capsula externa and the capsula extrema (white matter).

Tracts in the internal capsule:1. Radiationes thalami2. Tractus corticopontinus3. Tractus corticobulbaris4. Tractus corticospinalis5. Tractus parietopontinus6. Tractus occipitopontinus7. Tractus temporopontinus

INTERNAL CAPSULE:INTERNAL CAPSULE:THE LOCALIZATION,THE LOCALIZATION,THE FIBER SYSTEMSTHE FIBER SYSTEMS

INSIDE THE INTERNALINSIDE THE INTERNALCAPSULE.CAPSULE.

MOTORMOTORTRACTS TRACTS

Thalamus: white matterThalamus: white matter

Outer envelope: external medullary lamina.Outer envelope: external medullary lamina.

Inner white matter: internal medullary Inner white matter: internal medullary lamina lamina →→ separates the nucleiseparates the nuclei..

Pedunculi thalami: fiber tracts connecting Pedunculi thalami: fiber tracts connecting the cerebral cortex with thalamic nuclei.the cerebral cortex with thalamic nuclei.

Thalamic radiation: every thalamic peduncle Thalamic radiation: every thalamic peduncle (anterior, superior, posterior, inferior), (anterior, superior, posterior, inferior), containing thalamocortical and containing thalamocortical and corticothalamic axons.corticothalamic axons.

Thalamus: grey matterThalamus: grey matter

Nuclei anteriores: fasciculus mammillothalamicus; cortical Nuclei anteriores: fasciculus mammillothalamicus; cortical projection: gyrus cinguli.projection: gyrus cinguli.

Nuclei mediales: amygdala, olfactory cortex, other thalamic Nuclei mediales: amygdala, olfactory cortex, other thalamic nuclei; cortical projection: anteromedial frontal lobe.nuclei; cortical projection: anteromedial frontal lobe.

Nuclei dorsales (pulvinar): visual association/memory functions.Nuclei dorsales (pulvinar): visual association/memory functions.

Nuclei ventrales: VA, VL (motor thalamus); VPL, VPM (sensory Nuclei ventrales: VA, VL (motor thalamus); VPL, VPM (sensory thalamus).thalamus).

Nuclei intralaminares: connection to sensory tracts, reticular Nuclei intralaminares: connection to sensory tracts, reticular formation, striatum, large areas of the neocortex (nonformation, striatum, large areas of the neocortex (non--specific specific activation system: arousal, attention).activation system: arousal, attention).

Nucleus reticularis thalami: GABAergic inhibitory neurons.Nucleus reticularis thalami: GABAergic inhibitory neurons.

Corpus geniculatum laterale (LGB): optic tract terminates here; Corpus geniculatum laterale (LGB): optic tract terminates here; projects to the visual cortex (occipital lobe).projects to the visual cortex (occipital lobe).

Corpus geniculatum mediale (MGB): auditory system (inferior Corpus geniculatum mediale (MGB): auditory system (inferior colliculus projects to it; MGB connects to the superior temporalcolliculus projects to it; MGB connects to the superior temporalgyrus (auditory neocortex).gyrus (auditory neocortex).

Afferents and efferents of theAfferents and efferents of themotor thalamusmotor thalamus

Ventralis anteriorVentralis anterior

AFF: globus pallidus, substantia nigra; AFF: globus pallidus, substantia nigra; EFF: frontal neocortex.EFF: frontal neocortex.

Ventralis lateralisVentralis lateralis

AFF: globus pallidus, nuclei cerebellares; AFF: globus pallidus, nuclei cerebellares; EFF: premotor cortex (frontal lobe).EFF: premotor cortex (frontal lobe).

Clinical: electrical stimulation of these Clinical: electrical stimulation of these nuclei is beneficial in some movement nuclei is beneficial in some movement disorders.disorders.

Afferents and efferents of theAfferents and efferents of thesensory thalamussensory thalamus

Nucleus ventralis posterolateralis (VPL):Nucleus ventralis posterolateralis (VPL):AFF: tractus spinothalamicus, lemniscus AFF: tractus spinothalamicus, lemniscus medialis. EFF: gyrus postcentralis.medialis. EFF: gyrus postcentralis.

Nucleus ventralis posteromedialis (VPM):Nucleus ventralis posteromedialis (VPM):AFF: lemniscus trigeminalis, tractus AFF: lemniscus trigeminalis, tractus solitariothalamicus. EFF: gyrus solitariothalamicus. EFF: gyrus postcentralis. postcentralis.

Intralaminar nucleiIntralaminar nuclei

Anterior and posterior groups.Anterior and posterior groups.

Connected to many neocortical areas.Connected to many neocortical areas.

Connected to the striatum.Connected to the striatum.

Afferent come from ascending sensory tracts, Afferent come from ascending sensory tracts, reticular formation, substantia nigra.reticular formation, substantia nigra.

Functions: Functions: movement regulation (striatum, movement regulation (striatum, substantia nigra)substantia nigra), , pain perceptionpain perception, , non non specific ascending activation systemspecific ascending activation system (arousal, (arousal, attention).attention).

Thalamus and painThalamus and pain

Nuclei posteriores:Nuclei posteriores: afferents from afferents from spinothalamic tract, efferents to the parietal spinothalamic tract, efferents to the parietal lobe.lobe.

Nuclei ventrales (ventralis posterior Nuclei ventrales (ventralis posterior inferior, basalisinferior, basalis ventralis medialis):ventralis medialis):afferents from lemniscus medialis, tr. afferents from lemniscus medialis, tr. spinothalamicus; efferents to the insular spinothalamicus; efferents to the insular cortex.cortex.

Nucleus centralis lateralis:Nucleus centralis lateralis: intralaminar intralaminar nucleus nucleus –– afferents from reticular formation afferents from reticular formation and from spinothalamic tract. Efferents to the and from spinothalamic tract. Efferents to the medial surface of the frontal lobe.medial surface of the frontal lobe.

NUCLEI,NUCLEI,

AFFERENTS,AFFERENTS,

EFFERENTS,EFFERENTS,

PEDUNCLES,PEDUNCLES,

NEOCORTICALNEOCORTICAL

RELATIONSRELATIONS

Glutamic acid transmitter andGlutamic acid transmitter andreceptor (NMDA) detected in receptor (NMDA) detected in the VPL.the VPL.Large calyciform synapseLarge calyciform synapse(scientific collection of the(scientific collection of theAnatomy Department).Anatomy Department).

Projection neuron (relay):Projection neuron (relay):excitatory (glutamic acid)excitatory (glutamic acid) Interneuron: inhibitory (GABA)Interneuron: inhibitory (GABA)

Thalamic relayThalamic relayneurons (principalneurons (principalneurons) whichneurons) whichproject to theproject to theneocortex.neocortex.

Sensory thalamusSensory thalamus(VPL) is depicted.(VPL) is depicted.

Intralaminar nucleiIntralaminar nucleiactivated following theactivated following theactivation of the reticularactivation of the reticularformation. The patientformation. The patientwas stimulated withwas stimulated withvisual stimuli (PET).visual stimuli (PET).The arrows show theThe arrows show thedirection of stimulusdirection of stimulusflow.flow.

DMVL

SN

FRONTAL PLANE MRI AND BRAIN SECTIONFRONTAL PLANE MRI AND BRAIN SECTION

A

DMVL

Nucleus subthalamicus

CI

Parasagittal MRI brain sectionParasagittal MRI brain section

Diencephalon and internal Diencephalon and internal capsule: blood supplycapsule: blood supply

Thalamus: anterior choroidal artery, posterior Thalamus: anterior choroidal artery, posterior communicating artery and proximal branches of communicating artery and proximal branches of the posterior cerebral artery. PCA supplies the the posterior cerebral artery. PCA supplies the posterior thalamus, others the middle and posterior thalamus, others the middle and anterior parts.anterior parts.

Hypothalamus: the proximal part of ACA has Hypothalamus: the proximal part of ACA has anterior hypothalamic branches. anterior hypothalamic branches.

Internal capsule: from proximal (central) Internal capsule: from proximal (central) branches of the MCA (central anterolateral branches of the MCA (central anterolateral arteries). Name of the largest: arteries). Name of the largest: lenticulostriate lenticulostriate arteryartery..

Thalamic symptomsThalamic symptoms(result from circulatory problems, (result from circulatory problems,

tumors, etctumors, etc……))

Sleep disturbancesSleep disturbances

Coma Coma

Thalamic painThalamic pain

Hemiparesis (motor thalamus !)Hemiparesis (motor thalamus !)

Hemianesthesia (sensory thalamus !)Hemianesthesia (sensory thalamus !)

Memory problems (amnesia) Memory problems (amnesia)

Movement disorders (motor thalamus !)Movement disorders (motor thalamus !)

The hypothalamus on theThe hypothalamus on thebasal surface (green line)basal surface (green line)

11 22 33

1.1. Supraoptic r.Supraoptic r.2.2. Tuberal r.Tuberal r.

3.3. Mammillary r.Mammillary r.(preoptic region is(preoptic region is

not shown)not shown)Median eminence isMedian eminence is

coloured in red.coloured in red.

Main hypothalamic nucleiMain hypothalamic nuclei

Preoptic and supraoptic regions:Preoptic and supraoptic regions:preoptic nuclei, nucleus preoptic nuclei, nucleus suprachiasmaticus, nucleus suprachiasmaticus, nucleus paraventricularis, nucleus paraventricularis, nucleus supraopticus.supraopticus.

Tuberal region:Tuberal region: nucleus arcuatus, nucleus arcuatus, nucleus ventromedialis, nucleus nucleus ventromedialis, nucleus dorsomedialis.dorsomedialis.

Mammillary region:Mammillary region: nuclei nuclei mammillares.mammillares.

Main hypothalamicMain hypothalamic tractstracts

Tractus hypothalamoTractus hypothalamo--hypophysialishypophysialis (to the (to the neurohypophysis).neurohypophysis).

Fornix:Fornix: from hippocampus.from hippocampus.

Fasciculus mammillothalamicusFasciculus mammillothalamicus (Vicq d(Vicq d’’Azyr):Azyr): from from mammillary body to anterior thalamic nuclei.mammillary body to anterior thalamic nuclei.

Fasciculus longitudinalis dorsalisFasciculus longitudinalis dorsalis (Sch(Schüütz):tz):hypothalamus hypothalamus –– brainstem preganglionic neuronsbrainstem preganglionic neurons

Tractus hypothalamoTractus hypothalamo--spinalis.spinalis.

Tractus retinohypothalamicus:Tractus retinohypothalamicus: to nucleus to nucleus suprachiasmaticus.suprachiasmaticus.

Fasciculus medialis telencephali (medial forebrain Fasciculus medialis telencephali (medial forebrain bundle):bundle): frontal lobe, septum, hypothalamus, frontal lobe, septum, hypothalamus, brainstem.brainstem.

Stria terminalis:Stria terminalis: amygdala and hypothalamus.amygdala and hypothalamus.

Transmitters and neurohormones Transmitters and neurohormones in the hypothalamusin the hypothalamus

Vasopressin (ADH), oxitocinVasopressin (ADH), oxitocin

Galanin, enkephalin, substance P, Galanin, enkephalin, substance P, neuropeptid Yneuropeptid Y

Dopamine, noradrenalin, serotonin, Dopamine, noradrenalin, serotonin, histamine, acetilcholinehistamine, acetilcholine

Glutamic acid, GABAGlutamic acid, GABA

Orexins, neurotensinOrexins, neurotensin

Releasing hormones (GHRH, GNRH, Releasing hormones (GHRH, GNRH, TRH, etcTRH, etc……))

Growth hormoneGrowth hormone--releasing hormone releasing hormone (GHRH) containing neurons in the (GHRH) containing neurons in the

arcuate nucleus (red dots)arcuate nucleus (red dots)

Donated by Prof. Bert Dudas, MDDonated by Prof. Bert Dudas, MD

Och: chiasma opticum; INF: infundibulum;Och: chiasma opticum; INF: infundibulum;ME: eminentia mediana; MB: corpus mammillareME: eminentia mediana; MB: corpus mammillareSagittal plane sectionsSagittal plane sections

The GHRH neuronsThe GHRH neurons(brown) receive(brown) receiveNPYNPY--peptidergicpeptidergic

innervation (black).innervation (black).(picture donated by(picture donated by

Prof. Bert Dudas, MD)Prof. Bert Dudas, MD)

Fx: fornixFx: fornixOt: tractus opticusOt: tractus opticusSon: nucleus supraopticusSon: nucleus supraopticusPvn: nucleus paraventricularisPvn: nucleus paraventricularisMb: corpus mammilareMb: corpus mammilare(star denotes the (star denotes the location of the cell)location of the cell)

Hypothalamus functions I.Hypothalamus functions I.

Neuroendocrine regulationNeuroendocrine regulation: nuclei : nuclei supraopticus, paraventricularis, arcuatus. supraopticus, paraventricularis, arcuatus. Tractus hypothalamohypophysealis.Tractus hypothalamohypophysealis.

Feeding (body weight) regulationFeeding (body weight) regulation: nucleus : nucleus lateralis (hunger), n. ventromedialis lateralis (hunger), n. ventromedialis (satiety).(satiety).

Body temperature regulationBody temperature regulation: area : area preoptica, nucleus anterior, nucleus preoptica, nucleus anterior, nucleus posteriorposterior

Hypothalamus functions II.Hypothalamus functions II.

SleepSleep--wakefulnesswakefulness: nucleus suprachiasmaticus : nucleus suprachiasmaticus (afferents from retina).(afferents from retina).

Fluid uptake regulationFluid uptake regulation: vasopressin as a : vasopressin as a hormone (nuclei supraopticus et hormone (nuclei supraopticus et paraventricularis).paraventricularis).

Autonomic nervous regulationAutonomic nervous regulation: tractus : tractus hypothalamospinalis, fasciculus longitudinalis hypothalamospinalis, fasciculus longitudinalis dorsalis (Schdorsalis (Schüütz).tz).

Behavioural and memory functionsBehavioural and memory functions: corpus : corpus mammillare (Vicq dmammillare (Vicq d’’Azyr bundle), nucleus Azyr bundle), nucleus ventromedialis, area hypothalamica lateralis.ventromedialis, area hypothalamica lateralis.

Circumventricular organs are in black: they are located around the 3rd

and 4th ventricles. They arechemoreceptor areas. Special ependyma

cells (tanycytes) and fenestrated capillaries characterize these organs.

Tanycytes in the 3rd ventricle: their processes terminate in Tanycytes in the 3rd ventricle: their processes terminate in hypothalamic nuclei (VMN, AN), in the median eminence (ME) and ohypothalamic nuclei (VMN, AN), in the median eminence (ME) and on n

the pial surface of the brain. Tanycytes are special ependymal cthe pial surface of the brain. Tanycytes are special ependymal cells ells lining the ventricle. They perform chemoreceptor function: senselining the ventricle. They perform chemoreceptor function: sense the the

concentration of glucose and amino acids in the CSF.concentration of glucose and amino acids in the CSF.

Tanycytes in the 3rd ventricle: their processes end on the brain surfaceand in the median eminence on fenestrated capillaries. Several cell

junctions are between the cell bodies lining the ventricle.

Thank you for Thank you for attentionattention……

Pictures:Pictures:1.1. Collection of the Szeged Anatomy Department.Collection of the Szeged Anatomy Department.2.2. BenninghoffBenninghoff--Drenckhahn: Anatomie. Urban&Fischer, Drenckhahn: Anatomie. Urban&Fischer,

2004.2004.3.3. SteriadeSteriade--JonesJones--McCormick: Thalamus. Elsevier, 1997.McCormick: Thalamus. Elsevier, 1997.4.4. EnglandEngland--Wakely: Color Atlas of the Brain and Spinal Cord. Wakely: Color Atlas of the Brain and Spinal Cord.

MosbyMosby--Elsevier, 2006.Elsevier, 2006.5.5. Carpenter: Core Text of Neuroanatomy. Williams&Wilkins, Carpenter: Core Text of Neuroanatomy. Williams&Wilkins,

1991.1991.6.6. Rodriguez et al.: Internat. Rev. Cytol. 247, 2010.Rodriguez et al.: Internat. Rev. Cytol. 247, 2010.