CerebralCerebral cortexcortex

WhiteWhite mattermatter WhiteWhite mattermatter ofof cerebralcerebral cortexcortex isis composedcomposed ofof neuronalneuronal axonsaxons && associatedassociated gliaglia

Commissural fiber s – to cortex of the other hemisphere
Association fiber s – to cortex of the same hemisphere
Projection fiber s – to and from lower structures Projection fibers CommissurCommissur alal fibersfibers

CCorpusorpus callosumcallosum (the(the largest)largest)
AAnteriornterior commissurecommissure –– betweenbetween amygdaloidamygdaloid bodiesbodies oror olfactoryolfactory bulbsbulbs onon bothboth sidessides
PosteriorPosterior commissurecommissure –– pupilpupil reflexreflex fibersfibers
HabenularHabenular commissurecommissure –– betweenbetween habenulaehabenulae
FornixFornix (commissure(commissure ofof fornix)fornix) Habenular commissure CorpusCorpus callosumcallosum

Splenium Body Genu

Rostrum CorpusCorpus callosumcallosum

10 cm CCorpusorpus callosumcallosum

Corpus callosum

Forceps minor (frontal)

Forceps major (occipital) Fornix Adhesio Interthalamica CommissuresCommissures

Posterior commissure

Pineal Gland

Anterior Commissure Lamina Terminalis Mammillary Body Optic Chiasm AnteriorAnterior commissurecommissure

Anterior Fibers commissure communicating between the temporal lobes (amygdala) AnteriorAnterior commissurecommissure –– 3D3D Habenular PosteriorPosterior && habenularhabenular commisurescommisures commissure (roof of pineal recess) Pineal gland

Posterior commissure (eye movements and light reflex) CorpusCorpus callosum,callosum, fornix,fornix, septumseptum pellucidumpellucidum

3rd ventricle FornixFornix

Fornix FornixFornix Body

Columns

Anterior Commissure

Mammillary Body TheThe fornixfornix

Alveus
Fimbria
Crus (posterior column)
Commissure of the fornix – Hippocampus → mammillary medial nucleus connects hippocampal formations of the two sides (rudimentary in humans)
Body
Column FornixFornix Fornix – 3D (of corpus callosum) IndusiumIndusium griseumgriseum AssociationAssociation FibersFibers

UU--shapedshaped fibersfibers fromfrom oneone corticalcortical areaarea toto anotheranother
ShortShort (usually(usually unnamed)unnamed) andand longlong AssociationAssociation FibersFibers

Short association fibers
fibrae arcuatae cerebri
Long association fibers  cingulum  superior longitudinal fasciculus  inferior longitudinal fasciculus  uncinate fasciculus  inferior frontooccipital fasciculus  arcuate fasciculus  vertical occipital fasciculus

CingulumCingulum

Parahippocampal ↔ ↔ ↔ ↔

Frontal/parietal Superior longitudinal fasciculus Arcuate bundle

Communication between visual association cortex and language centers Motor cortex (mouth & tongue)

Visual association cortex ProjectionProjection fibersfibers

CorticofugalCorticofugal (from(from thethe cortexcortex toto lowerlower structures)structures)  CorticofugalCorticofugal projectionprojection fibresfibres convergeconverge fromfrom allall directionsdirections toto formform thethe densedense subcorticalsubcortical whitewhite mattmatterer massmass ofof thethe coronacorona radiataradiata  TheThe coronacorona radiataradiata isis continuouscontinuous withwith thethe internalinternal capsulecapsule ,, whichwhich containscontains thethe majoritymajority ofof thethe corticalcortical projectionprojection fibresfibres
CorticopetalCorticopetal (to(to thethe cortexcortex fromfrom lowerlower structures)structures) InternalInternal capsulecapsule

(corona radiata)

Pyramidal tract CConvergenceonvergence ofof corticalcortical projectionprojection fibresfibres throughthrough ththee coronacorona radiataradiata intointo thethe cerebralcerebral pedunclespeduncles InternalInternal capsulecapsule Anterior Limb ProjectionProjection Genu fibersfibers -- toto and from the and from the Posterior cortex.cortex. Limb

The posterior limbs of the IC become what structure? The cerebral peduncle s InternalInternal capsulecapsule Anterior Limb

Caudate Genu

Putamen Posterior Limb Thalamus

Three regions of the internal capsule separate three regions of gray matter. Internal capsule – 3D InternalInternal capsulecapsule –– 3D3D InternalInternal capsulecapsule (ant.(ant. limb)limb) –– 3D3D cortex thalamus SomatotopicSomatotopic cortex basal ganglia arrangementarrangement ofof fibersfibers corticopontine inin internalinternal capsulecapsule

Corticobulbar (to cranial nerve nuclei)

F - face A - arm motor fibers L - leg

f - face a - arm sensory fibers l - leg InfarctionInfarction ofof thethe posteriorposterior limblimb ofof thethe internalinternal capsulecapsule causcaus eses aa "pure"pure motormotor stroke"stroke"

MRI of a 51 -year -old patient with hypertension. The patient complained of weakness of the right side of the face and the right arm and leg, which had developed over a 5 -h period. There was no F sensory loss or problems with A L language or cognition. The MRI f a revealed a small infarction in the l internal capsule ( arrow ), which destroyed axons descending from the motor cortex, thus causing a "pure motor stroke" in this patient RhinencephalonRhinencephalon

SmellSmell brainbrain RhinencephalonRhinencephalon vsvs LimbicLimbic lobelobe

IInn phylogeneticallyphylogenetically lowerlower animalsanimals ,, thethe termsterms limbiclimbic lobelobe andand smellsmell brainbrain (rhinencephalon)(rhinencephalon) areare usedused synonymouslysynonymously
InIn humanshumans  limbiclimbic lobelobe hashas veryvery littlelittle ifif anyany primaryprimary olfactorolfactoryy function.function.  rhinencephalonrhinencephalon isis primarilyprimarily concernedconcerned withwith olfactioolfactionn butbut hashas somesome reciprocalreciprocal relationshipsrelationships withwith partsparts ofof otherother limbiclimbic systemsystem regionsregions ComponentsComponents ofof rhinencephalonrhinencephalon

OlfactoryOlfactory nervenerve (CN(CN I)I) rootletsrootlets
OlfactoryOlfactory bulbbulb
OlfactoryOlfactory tracttract
OlfactoryOlfactory striaestriae
PrimaryPrimary olfactoryolfactory cortexcortex OlfactoryOlfactory nervenerve && bulbbulb OlfactoryOlfactory nervenerve && bulbbulb

The olfactory nerve (CN I) is composed of unmyelinated axons of the olfactory receptor cells in the nasal mucosa.
CN I axons pierce the cribriform plate of the ethmoid bone, enter CN I the cranial cavity, and terminate on neurons in the olfactory bulb
Olfactory bulb is the main relay station in the olfactory pathways OlfactoryOlfactory bulbbulb && tracttract OlfactoryOlfactory bulbbulb structurestructure (4(4 mainmain layers)layers)

Olfactory nerve layer - incoming olfactory nerve fibers
Glomerular layer - synap se between the olfactory nerve axons and the dendrites of olfactory bulb neurons (mitral and tufted cells ); contains periglomerular interneurons
External plexiform layer - tufted neurons, some granule cells, and a few mitral cells with their processes
Mitral cell layer - large neurons (mitral cells )
Granule cell layer - small granule neurons (interneurons) and processes of granule and mitral cells; it also contains incoming fibers from other cortical regions

OlfactoryOlfactory bulbbulb outputoutput

TheThe projectionprojection neuronsneurons ofof thethe olfactoryolfactory bulbbulb areare thethe tuftedtufted andand mitralmitral cellscells OlfactoryOlfactory tracttract

Cribiform plate OlfactoryOlfactory sstriaetriae

AtAt itsits caudalcaudal extremity,extremity, justjust rostralrostral toto thethe anterioanteriorr perforatedperforated substance,substance, thethe olfactoryolfactory tracttract dividesdivides inintoto 33 striae:striae:  lateral olfactory stria → primary olfactory cortex  medial olfactory stria → septal area (emotions associated with olfactory stimuli)  intermediate olfactory stria → blends with the anterior perforated substance
EachEach striastria isis coveredcovered byby aa thinthin layerlayer ofof graygray mattematterr knownknown asas anan olfactoryolfactory gyrusgyrus
TheThe 33 striaestriae areare interconnectedinterconnected byby thethe diagonaldiagonal bandband ofof Broca,Broca, aa bundlebundle ofof subcorticalsubcortical fibersfibers inin frontfront ofof ththee opticoptic tracttract OlfactoryOlfactory striaestriae

Anterior perforated substance CentralCentral olfactoryolfactory projectionsprojections The olfactory system is thus unique among the sensory systems in that it does not include a thalamic relay from primary receptors en route to a cortical region

Olfactory nerve & bulb

Piriform cortex (paleocortex)

Thalamus

Neocortex OlfactoryOlfactory ccortexortex

PrimaryPrimary (( consciousconscious perceptionperception ofof olfactoryolfactory stimulistimuli ))  ppyriformyriform cortexcortex -- thethe regionregion onon eacheach sideside ofof andand beneathbeneath thethe laterallateral olfactoryolfactory stria;stria; itit isis alsoalso callcalleded thethe laterallateral olfactoryolfactory gyrusgyrus →→ formsforms anterioranterior halfhalf ofof thethe uncusuncus  pperiamygdaloideriamygdaloid areaarea -- areaarea isis dorsaldorsal andand rostralrostral toto thethe amygdaloidamygdaloid nuclearnuclear complexcomplex →→ formsforms posteirorposteiror halfhalf ofof thethe uncusuncus
SecondarySecondary –– entorhinalentorhinal areaarea (BA28)(BA28) OlfactoryOlfactory cortexcortex

Entorhinal cortex (area; EA) CentralCentral olfactoryolfactory projectionsprojections

pons LLimbicimbic lobelobe vsvs limbiclimbic systemsystem

TheThe termterm limbiclimbic lobelobe refersrefers toto thethe structuresstructures thatthat formform aa limbuslimbus (ring(ring oror border)border) aroundaround thethe brainbrain stemstem →→ subcallosalsubcallosal gyrus,gyrus, cingulatecingulate gyrus,gyrus, isthmus,isthmus, parahippocampalparahippocampal gyrus,gyrus, andand uncusuncus
TheThe termterm limbiclimbic systemsystem refersrefers toto thethe limbiclimbic lobelobe andand thethe structuresstructures connectedconnected toto itit
LimbicLimbic systemsystem structuresstructures playplay importantimportant rolesroles inin emotionalemotional behavior,behavior, memory,memory, homeostatichomeostatic responses,responses, sexualsexual behavior,behavior, andand motivationmotivation LimbicLimbic systemsystem mediatesmediates affectiveaffective behaviorbehavior

EmotionEmotion

Joy and Despair ConceptConcept ofof limbiclimbic systemsystem

BrocaBroca (1877)(1877) -- ‘‘LaLa GrandGrand LobeLobe LimbiqueLimbique ’’
PapezPapez (1937)(1937) -- ‘‘LimbicLimbic CircuitCircuit ’’ -- emotionemotion
MacLeanMacLean (1952)(1952) -- ‘‘LimbicLimbic SystemSystem ’’ -- visceralvisceral brainbrain
NautaNauta (1972)(1972) -- ‘‘SeptoSepto --hypothalamohypothalamo -- mesencephalicmesencephalic continuumcontinuum ’’ PAUL BROCA JAMES PAPEZ (1824-1880) (1883-1958) LimbicLimbic lobelobe structuresstructures

Subcallosal gyrus, inferior to the genu and rostrum of the corpus callosum, just anterior to the lamina terminalis
Cingulate gyrus (mesocortex)
Isthmus of the cingulate gyrus, posterior and inferior to the splenium of the corpus callosum
Parahippocampal gyrus (paleocortex) and the underlying hippocampal formation (archicortex )
Uncus LLimbicimbic systemsystem →→ medialmedial wallwall ofof thethe hemispherehemisphere LimbicLimbic lobelobe –– ventralventral viewview PapezPapez circuitcircuit

alveolar path EntorhinalEntorhinal CortexCortex perforant path (Area(Area 28)28) cingulum

HippocampalHippocampal CingulateCingulate FormationFormation GyrusGyrus

fornix thalamocortical radiation

MammillaryMammillary AnteriorAnterior BodyBody ThalamicThalamic NucleiNuclei mammillothalamic tract PapezPapez circuitcircuit

A →B → C → D → A A. Hippocampal formation B. Mammillary body C. Thalamic anterior nucleus D. Cingulate gyrus

1. fornix 2. mammillothalamic tract 3. thalamocortical radiation 4. cingulum LimbicLimbic systemsystem

limbiclimbic lobelobe ++
SeptalSeptal nucleinuclei (septal(septal cortex)cortex)
AmygdalaAmygdala
HypothalamusHypothalamus (particularly(particularly thethe mamillarymamillary body)body)
ThalamusThalamus (particularly(particularly thethe anterioranterior andand medialmedial nuclnuclei)ei)
BrainBrain stemstem reticularreticular formationformation
EpithalamusEpithalamus
NeocorticalNeocortical areasareas inin thethe basalbasal frontotemporalfrontotemporal regioregionn
OlfactoryOlfactory cortexcortex (rhinencephalon)(rhinencephalon)
VentralVentral partsparts ofof thethe striatumstriatum LimbicLimbic structuresstructures MainMain componentscomponents ofof thethe limbiclimbic systemsystem

OlfactoryOlfactory CortexCortex

Septo - Hypothalamo - Mesencephalic Continuum Spinal LimbicLimbic Cord HippocampalHippocampal SeptalSeptal HypothalamusHypothalamus MidbrainMidbrain & FormationFormation RegionRegion AreaArea Brain Stem

AmygdaloidAmygdaloid NuclearNuclear ComplexComplex ComponentsComponents ofof thethe limbiclimbic systemsystem –– CC shapeshape HippocampusHippocampus TheThe hippocampushippocampus HippocampalHippocampal formationformation

HippocampusHippocampus properproper (Ammon ’s horn, Cornu Ammonis = CA)
DentateDentate GyrusGyrus (DG)(DG)
SubiculumSubiculum (S)(S)

CA

DG CA DG CA

S HippocampalHippocampal formationformation

 CC--shapedshaped structure,structure, anan infoldinginfolding ofof thethe parahippocampalparahippocampal gyrusgyrus intointo thethe inferiorinferior (temporal)(temporal) hornhorn ofof thethe latelateralral ventricleventricle  StartsStarts inin temporaltemporal lobelobe withwith hippocampushippocampus  PosteriorPosterior hippocampushippocampus sendssends efferentefferent projectionsprojections (c(calledalled fimbria)fimbria)  FimbriaFimbria becomebecome aa detacheddetached bundlebundle calledcalled thethe fornixfornix (near(near spleniumsplenium ofof CC)CC)  FornixFornix travelstravels anterioranterior inin thethe inferiorinferior edgeedge ofof thethe septumseptum pellucidumpellucidum HippocampalHippocampal formationformation

Hippocampus HippocampusHippocampus && amygdalaamygdala

Amygdala Uncus

Hippocampus

Temporal Horn of Lateral Ventricle HippocampalHippocampal formationformation atat variousvarious levelslevels

resembles sea horse in coronal section HippocampalHippocampal formationformation (lateral(lateral view)view) HippocampalHippocampal formationformation (medial(medial view)view) HippocampalHippocampal formationformation (medial(medial view;view; magnified)magnified) HippocampalHippocampal formationformation -- archicortexarchicortex

Molecular Archicortex - 3 layers Pyramidal Polymorphic Hippocampus Proper Molecular layer Polymorphic Pyramidal layer Pyramidal layer Granule Polymorphic layer Molecular Dentate Gyrus Molecular layer Subiculum Granule cell layer Polymorphic layer Subiculum Transitional type between archicortex & paleocortex NNeocortexeocortex vsvs archicortexarchicortex

Neocortex Archicortex AmmonAmmon ’’ss hornhorn (( CornuCornu AmmonisAmmonis,, CA)CA) HippocampalHippocampal formationformation

DentateDentate gyrus,gyrus, CA1,CA1, CA2,CA2, CA3,CA3, CA4,CA4, subiculumsubiculum DevelopmentDevelopment ofof thethe hippocampushippocampus

1. dentate gyrus 2. hippocampus proper 3. subiculum

HS: hippocampal sulcus TH: temporal horn (LV) EstimatedEstimated timetime ofof developmentdevelopment ofof variousvarious brainbrain regiregionsons

2 mo 4 mo

Modified from Bayer SA et al. Neurotoxicology 14:83–144, 1993 ConnectionsConnections ofof hippocampalhippocampal formationformation

IntrinsicIntrinsic connectionsconnections  classicclassic trisynaptictrisynaptic pathwaypathway
AfferentAfferent connectionsconnections  perforantperforant andand alveolaralveolar pathpath
EfferentEfferent connectionsconnections  fornixfornix AfferentAfferent && efferentefferent hippocampalhippocampal connectionsconnections MMajorajor typestypes ofof neuronsneurons inin thethe hippocampushippocampus

Principal neuron – pyramidal neuron (1.2 million per side) – glutamatergic
Intrinsic neurons – regulate pyramidal cells; GABAergic Extrinsic & intrinsic hippocampal circuits

Fornix Gyrus dentatus CA3 CA2 CA4

2

Entorhinal cortex 1 3 S

4 CA1

5 MMajorajor afferentsafferents toto thethe hippocampalhippocampal formationformation MMajorajor eefferentsfferents fromfrom thethe hippocampalhippocampal formationformation

Fornix Precommissural vsvs postcommissural fornixfornix

Fornix

postcommissural fornix

anterior commissure precommissural fornix Precommissural vsvs postcommissural fornixfornix

anterior Precommissural

Anterior Commissure

Postcommissural posterior Precommissural vsvs postcommissural fornixfornix

PPrecommissuralrecommissural fornixfornix (25%)(25%)  septalseptal nucleinuclei  medialmedial frontalfrontal cortexcortex  anterioranterior hypothalamushypothalamus  ventralventral striatumstriatum
PostPost commissuralcommissural fornixfornix (75%)(75%)  mamillarymamillary bodybody (medial(medial nucleus)nucleus)  anterioranterior nuclenucle ii ofof thalamusthalamus  midbrainmidbrain tegmentumtegmentum EEntorhinalntorhinal --hippocampalhippocampal --entorhinalentorhinal circuitcircuit

The synapses in this circuit are all excitatory EEntorhinalntorhinal --hippocampalhippocampal --entorhinalentorhinal circuitcircuit

Gyrus dentatus CA3 CA2 CA4

2

Entorhinal cortex 1 3 S 5

4 CA1

Via the entorhinal cortex, the hippocampal formation can influence virtually all association areas of the temporal, parietal, and frontal lobes HHippocampusippocampus isis importantimportant forfor declarativedeclarative (explicit)(explicit) memorymemory Temporal categories of human memory

hippocampus-dependent neocortex-dependent Practice, conversation, context

< seconds seconds to minutes days to years EffectsEffects ofof hippocampalhippocampal lesionslesions onon memorymemory

BilateralBilateral ablationablation ofof thethe hippocampushippocampus inin humanshumans (usually(usually involvinginvolving adjacentadjacent regionsregions asas well)well) resultresultss inin aa lossloss ofof recentrecent (60(60 s)s) memorymemory andand thethe inabilityinability toto sstoretore newlynewly learnedlearned factsfacts (anterograde(anterograde amnesia)amnesia)
LLongong --termterm memoriesmemories remainremain intactintact
UnilateralUnilateral ablationablation ofof thethe hippocampushippocampus inin humanshumans dodoeses notnot affectaffect memorymemory toto aa significantsignificant degreedegree
SimilarSimilar toto hemispherichemispheric specialization,specialization, thethe leftleft hippocampushippocampus isis specializedspecialized forfor verbalverbal memorymemory andand ththee rightright hippocampushippocampus forfor nonverbalnonverbal memorymemory Patient H.M. & memory Patient H.M. & memory

Medial-temporal lobe resection

No short-term declarative memory Anterograde amnesia PatientPatient H.M.H.M.

Henry Gustav Molaison (February 26, 1926 – December 2, 2008) Patient H.M. HippocampusHippocampus isis aa sitesite ofof persistentpersistent generationgeneration ofof neuronsneurons throughoutthroughout lifelife

Progenitor Immature neuron Mature neuron Functional neurogenesis Gyrus Dentatus

(van Praag et al, Nature, 2002) Physiological Conditions Affecting Neurogenesis (Dentate gyrus )

• Increasedproliferation  environmental enrichment, learning  physical exercise

• Decreasedproliferation  ageing  maternal separation Drugs Affecting Neurogenesis (Gyrus dentatus )

• Increasedproliferation  antidepressants (TCA & SSRI); ECT  haloperidol  lithium  estrogen, aldosterone  inhibitory amino acids (GABA)

• Decreasedproliferation  corticosteroids  opiates (morphine)  excitatory amino acids (GLU) Clinical Conditions Affecting Neurogenesis (Gyrus dentatus ) • Increased proliferation  ischemia  seizures  trauma  degeneration (dementia)

• Decreased proliferation  stress (depression)  irradiation  inflammation (meningitis)  chronic alcoholism Function of adult hippocampal neurogenesis (at least in rodents)

Practice, conversation, context

< seconds seconds to minutes days to years

Levels of neurogenesis determine the hippocampus- dependent period of memory HippocampalHippocampal rudimentsrudiments

IndusiumIndusium griseumgriseum ((supracallosalsupracallosal gyrus)gyrus)  portion of the hippocampal formation that remained attached to the corpus callosum during its development  merges with the dentate and parahippocampal gyri by way of the fasciola r gyrus  2 pairs of its white matter fasciolar gyrus terminate in the hippocampal formation → medial and lateral longitudinal striae
FasciolarFasciolar gyrusgyrus –– linkslinks indusiumindusium griseumgriseum withwith dentatedentate && parahippocampalparahippocampal gyrigyri MMedialedial andand laterallateral longitudinallongitudinal striaestriae ofof indusiumindusium griseumgriseum Amygdala (L. almond) Relationship of amygdala and hippocampal formation LocationLocation ofof amygdalaamygdala (ventral(ventral view)view)

Amygdala Uncus In the tip of the temporal lobe beneath the cortex of the uncus Hippocampus and rostral to the hippocampus and the inferior horn of the lateral ventricle

Temporal Horn of Lateral Ventricle Location of amygdala (cross section)

Uncus

PHG NucleiNuclei ofof amygdalaamygdala

CCorticomedialorticomedial --centralcentral groupgroup (dorsomedial)(dorsomedial)  relativelyrelatively smallsmall andand isis phylogeneticallyphylogenetically olderolder  connectionsconnections withwith thethe phylogeneticallyphylogenetically olderolder regionsregions ((olfactoryolfactory bulb,bulb, hypothalamus,hypothalamus, andand brainbrain stemstem ))
BBasolateralasolateral groupgroup (ventrolateral)(ventrolateral)  largerlarger andand phylogeneticallyphylogenetically moremore recentrecent  connectionsconnections withwith thethe cerebralcerebral cortexcortex ((prefrontal,prefrontal, temporal,temporal, occipital,occipital, andand insularinsular corticescortices –– associationassociation cortices)cortices) AmygdalaAmygdala -- nucleinuclei

Corticomedial-central group

midline

Basolateral group AfferentsAfferents toto amygdalaamygdala

Basolateral group

Prefrontal cortex

Thalamus (DM nucleus)

Hypothalamus (VM nucleus) TheThe basolateralbasolateral nuclearnuclear groupgroup isis intimatelyintimately andand reciprocallyreciprocally connectedconnected withwith thethe prefrontalprefrontal cortexcortex viavia thethe uncinateuncinate fasciculusfasciculus EfferentsEfferents fromfrom amygdalaamygdala

SStriatria terminalisterminalis (dorsal(dorsal amygdalofugalamygdalofugal pathway)pathway)  fromfrom thethe corticomedialcorticomedial groupgroup ofof nucleinuclei  CC--shaped,shaped, overover thethe thalamus,thalamus, medialmedial toto thethe caudatecaudate
VVentralentral amygdalofugalamygdalofugal pathwaypathway  fromfrom thethe basolateralbasolateral && centralcentral groupgroup
TheThe twotwo amygdalaamygdala communicatecommunicate withwith eacheach otherother throughthrough thethe striastria terminalisterminalis andand thethe anterioranterior commissurecommissure
NuclearNuclear groupsgroups withinwithin eacheach amygdaloidamygdaloid nuclearnuclear complexcomplex communicatecommunicate withwith eacheach otherother viavia shortshort fiberfiber systemssystems StriaStria terminalisterminalis Stria terminalils, ventral amygdalofugal pathway & anterior commissure EfferentsEfferents fromfrom amygdalaamygdala BedBed nucleusnucleus ofof striastria terminalisterminalis -- extendedextended amygdalaamygdala

A. Bed nucleus of stria terminalis (BST) B. centromedial amygdala C. basolateral amygdala D. cortical amygdala E. connections between BST & amygdala

1. stria terminalis ConnectionsConnections && functionsfunctions ofof amygdalaramygdalar nucleinuclei OtherOther functionsfunctions ofof amygdalaamygdala

StimulationStimulation ofof thethe amygdalaamygdala enhancesenhances thethe orientingorienting responseresponse toto novelnovel eventsevents
LLinkink ss thethe perceptionperception ofof thethe faceface expressionexpression (constructed(constructed inin superiorsuperior temporaltemporal cortex)cortex) toto thethe retrievalretrieval ofof knowledgeknowledge aboutabout itsits emotionalemotional andand socialsocial meaningmeaning ((mostmost evidentevident forfor negativelynegatively valencedvalenced emotionsemotions -- fear,fear, anger,anger, sadness)sadness)
StimulationStimulation ofof thethe amygdalaamygdala hashas beenbeen associatedassociated witwithh aa varietyvariety ofof sexualsexual behaviorsbehaviors ,, includingincluding erection,erection, ejaculation,ejaculation, copulatorycopulatory movements,movements, andand ovulationovulation
DestructionDestruction ofof bothboth amygdalasamygdalas inin humanshumans hashas beenbeen donedone toto relieverelieve intractableintractable epilepsyepilepsy andand treattreat violentviolent behaviorbehavior
CControlontrol ofof autonomicautonomic nervousnervous systemsystem functionfunction inin relationrelation toto previousprevious experiencesexperiences EmotionEmotion && amygdalaamygdala

SI, AI, VI – primary sensory/auditory/visual areas
SA, AA, VA – association sensory/auditory/visual areas
MA – multimodal association areas
OB – olfactory bulb SSeptaleptal areaarea

SSeptumeptum pellucidumpellucidum  thinthin leafleaf thatthat separatesseparates thethe laterallateral ventriclesventricles  mademade upup ofof gliaglia andand linedlined byby ependymaependyma
SSeptumeptum verumverum  ventralventral toto thethe septumseptum pellucidum,pellucidum, betweenbetween thethe subcallosalsubcallosal gyrusgyrus rostrallyrostrally andand thethe anterioranterior commissurecommissure //anterioranterior hypothalamushypothalamus caudallycaudally  nucleinuclei  septal nuclei (poorly developed in humans)  diagonal band of Broca  bed nucleus of the stria terminalis → amygdala  nucleus accumbens septi → basal ganglia SSeptaleptal areaarea SSeptaleptal areaarea inin relationrelation toto thethe restrest ofof thethe limbiclimbic systemsystem SSeptaleptal nucleinuclei andand septumseptum pellucidumpellucidum -- betweenbetween thethe corpuscorpus callosumcallosum andand fornixfornix SSeptaleptal areaarea hashas reciprocalreciprocal connectionsconnections withwith ::

HippocampusHippocampus (the(the majormajor connection)connection) –– viavia fornix;fornix; topographicallytopographically organizedorganized (( specificspecific areasareas ofof thethe hippocampushippocampus projectproject onon specificspecific septalseptal nuclei)nuclei)
AAmygdalamygdala –– viavia striastria terminalisterminalis andand thethe ventralventral amygdalofugalamygdalofugal pathwaypathway
HHypothalamusypothalamus ((preoptic,preoptic, anterior,anterior, paraventricular,paraventricular, andand laterallateral nuclei)nuclei) –– viavia medialmedial forebrainforebrain bundlebundle
MidbrainMidbrain ((periaqueductalperiaqueductal graygray && ventralventral tegmentaltegmental areaarea )) –– viavia medialmedial forebrainforebrain bundlebundle
HHabenularabenular nuclenucle ii –– viavia striastria medullarismedullaris thalamithalami
CCingulateingulate gyrusgyrus
TThalamushalamus -- dorsomedialdorsomedial andand thethe anterioranterior nucleinuclei Septal nuclei SSeptaleptal areaarea –– summarysummary ofof connectionsconnections SSeptaleptal areaarea -- aa sitesite ofof interactioninteraction betweenbetween limbiclimbic andand diencephalicdiencephalic structuresstructures

DestructionDestruction ofof thethe septalseptal nucleinuclei →→ behavioralbehavioral overreactionoverreaction toto manymany environmentalenvironmental stimulistimuli ((sexualsexual andand reproductivereproductive behavior,behavior, feeding,feeding, drinking,drinking, andand thethe ragerage reactionreaction ))
ChemicalChemical stimulationstimulation inin thethe septalseptal areaarea usingusing acetylcholineacetylcholine resultsresults inin euphoriaeuphoria andand sexualsexual orgasmorgasm
MarkedlyMarkedly increasedincreased sexualsexual activityactivity hashas beenbeen reportedreported inin humanshumans afterafter septalseptal damagedamage DiagonalDiagonal bandband ofof BrocaBroca Corpus callosum (removed)

Septal nuclei

Amygdala DiagonalDiagonal bandband ofof BrocaBroca (DBB)(DBB) && NucleusNucleus basalisbasalis ofof MeynertMeynert (NBM)(NBM)

Fornix AC

DBB NBM

Cholinergic neurons TheodorTheodor MeynertMeynert (1833 -1892)

• Austrian Neurologist • Professor of Neurology and Psychiatry in Wien University • Teacher of Sigmund Freud • Use serial sections in histology of nervous system

• Basal Nucleus of Meynert in substantia innominata • Dorsal tegmental decussation of Meynert BasalBasal forebrainforebrain areaarea (structures deep to the anterior perforating substance)

BASAL FOREBRAIN AREA

Ventral striatum Ventral pallidum Basal nucleus of Meynert (Ch4) Bed nucleus of stria terminalis

Cholinergic Cell Groups 1. Ch1 (Medial Septal Nucleus) 2. Ch2 (Nucleus of Diagonal Band of Broca) 3. Ch3 (Nucleus of Diagonal Band of Broca) 4. Ch4 (Basal Nucleus of Meynert) 5. Ch5 (Pedunculopontine Tegmental Nucleus) BasalBasal forebrainforebrain areaarea (structures(structures deepdeep toto thethe anterioranterior perforatingperforating substasubstance)nce)

Anterior perforated substance TThehe integrativeintegrative functionfunction ofof thethe limbiclimbic systemsystem (the(the limbiclimbic loop)loop)

Afferent Efferent

Afferent limb of the loop → collaterals from the pathway connecting neocortical association cortices with the prefontal cortex
Efferent limb of the loop → projections from the limbic centers to the prefrontal association cortex
Autonomic and endocrine centers are reciprocally connected with the limbic system centers that receive cortical collaterals MainMain functionfunction ss ofof thethe limbiclimbic systemsystem

HHippocampusippocampus →→ memorymemory
AAmygdalamygdala →→ emotionemotion andand sexualitysexuality
AAnteriornterior cingulatecingulate gyrusgyrus →→ motivationmotivation
OOrbitofrontalrbitofrontal cortexcortex →→ socialsocial behaviorbehavior LimbicLimbic systemsystem && AlzheimerAlzheimer ’’ss diseasedisease

& basal nucleus LimbicLimbic systemsystem && TLETLE RegressionRegression ofof thethe limbiclimbic systemsystem inin evolutionevolution

OB

Archi & paleocortex

Mesocortex

Neocortex EvolutionEvolution andand thethe limbiclimbic systemsystem

1. Protoreptilian Brain (R Complex) ---- Instinct

2. Paleomammalian Brain --- Limbic System ---- Emotion

3. Neomammalian Brain --- Neocortex --- Analytical, Reasoning LimbicLimbic systemsystem checklistchecklist