THE CEREBRAL CORTEXTHE CEREBRAL CORTEX

Institute of Anatomy, 1st Medical FacultyInstitute of Anatomy, 1st Medical FacultyR. DrugaR. Druga

CORTEX CEREBRICORTEX CEREBRI Definice, Definice, DefinitionDefinition Neocortex, AllocortexNeocortex, Allocortex Vývoj hemisféry a neokortexuVývoj hemisféry a neokortexu Development of the neocortexDevelopment of the neocortex Struktura neokortexuStruktura neokortexu Structure of the neocortexStructure of the neocortex Hlavní typy neuronůHlavní typy neuronů Main types of neuronsMain types of neurons

DP = dorsal pallium

LGE= lateral ganglionic eminence

MGE = medial ganglionic eminence

MGE + LGE

NEOCORTEXNEOCORTEX

Laminar pattern – 6 layersLaminar pattern – 6 layers 10 – 20 billion neurons10 – 20 billion neurons 95 % surface of the hemisphere95 % surface of the hemisphere

LOBES OF THE HERMISPHERE

Nissl staining

Archicortex (Hippocampus, field CA1- 3 layers

Str. or.

Str, pyr.

Str. mol.

Paleocortex (Olfactory cortex – 3 layers)

I. II, III.

Astrocyty (imunoreaction GFAP)

NEOCORTEX,NEOCORTEX, types of neuronstypes of neurons

Pyramidal Pyramidal neuronsneurons

Apical and basal Apical and basal dendritesdendrites

Dendritic spinesDendritic spines Excitatory (glutamate)Excitatory (glutamate) Homogenous groupHomogenous group 60 – 70 %60 – 70 %

Non-pyramidal Non-pyramidal neuronsneurons

AspinyAspiny Heterogenous groupHeterogenous group Inhibitory (Inhibitory (GABA)GABA) 30 – 40 %30 – 40 %

Pyramidal neurons

Layer V.

M I

Golgi impregnation

Korové interneurony

Projection neurons, excitatatory, glutamate

Long axons

Local circuit neurons, inhibitory, GABA, short axons

PV – ir (GABAergic)

CALRETININ – IR (GABAergic)

My investigations showed that the functional superiority of the human brain is intimately bound up with the prodigious abundance and unusual wealth of forms of the so-called neurons with the short axons.

S. R. y Cajal: Recuerdos de mi vida. 1917.

Interneurons are butterflies of the soul.

S.R. y Cajal 1923

Petilla de Aragon (Cajal birthplace) 2005

„Petilla Convention“

K.Brodmann, 1907, 1911

11 regions

52 areas

Layers of the neocortex

Neocortex - vrstvy

Characteristics of layersCharacteristics of layers

I.. Molecular layer – local inhibitory interneuronsI.. Molecular layer – local inhibitory interneurons II. External granular – association neuronsII. External granular – association neurons III. External pyramidal – commissural neuronsIII. External pyramidal – commissural neurons IV. Internal granular – receives thalamocortical IV. Internal granular – receives thalamocortical

projectionsprojections V. Internal pyramidal – projecting neurons (basal V. Internal pyramidal – projecting neurons (basal

ganglia, brain stem, spinal cordganglia, brain stem, spinal cord VI. Multiform layer – corticothalamic neurons VI. Multiform layer – corticothalamic neurons

V – basal ganglia

brain stem

spinal cord

VI - thalamus

Excitatory connections in the neocortexExcitatory connections in the neocortex

Layer 4 – termination of Layer 4 – termination of thalamocortical projectionsthalamocortical projections

Layer 4 – projects to layer 3Layer 4 – projects to layer 3

Layer 3 – projects to layer 5Layer 3 – projects to layer 5

Association areas

Afferent neocortical connectionsAfferent neocortical connections

Thalamic nucleiThalamic nuclei (thalamocortical fibers) (thalamocortical fibers) AmygdalaAmygdala ClaustrumClaustrum HypothalamusHypothalamus

Nc. basalis (Meynert)-cholinergic systemNc. basalis (Meynert)-cholinergic system Raphe nuclei (serotonin)Raphe nuclei (serotonin) Locus coeruleus (noradrenalin)Locus coeruleus (noradrenalin) Subst. Nigra (VTA) - dopaminSubst. Nigra (VTA) - dopamin

Efferent neocortical connections Efferent neocortical connections (excitatory, glutamatergic)(excitatory, glutamatergic)

Thalamic nucleiThalamic nuclei

Basal ganglia (striatum, amygdala, claustrum)Basal ganglia (striatum, amygdala, claustrum)

Brain stem (pretectal area, tectum, nc. ruber, RF, Brain stem (pretectal area, tectum, nc. ruber, RF, nuclei of cranial nerves, pontine ncc., nc. gracilis, nuclei of cranial nerves, pontine ncc., nc. gracilis, nc. cuneatus)nc. cuneatus)

Spinal cord ( corticospinal pathway, interneurons, Spinal cord ( corticospinal pathway, interneurons, motoneurons)motoneurons)

Motor cortical areaMotor cortical area

G. Fritsch and E. Hitzig (1870) G. Fritsch and E. Hitzig (1870) demonstrated that electrical demonstrated that electrical stimulation of the dog´s frontal lobe stimulation of the dog´s frontal lobe results in contralateral muscular results in contralateral muscular contractions (movements)contractions (movements)

Primary motor area, M I

Motor homunculus

Primary motor area M IPrimary motor area M I Precentral gyrus, area 4Precentral gyrus, area 4 Part of the cortex from which movements are easily Part of the cortex from which movements are easily

produced by electrical stimulationproduced by electrical stimulation Motor homunculus (overrepresentation muscles of Motor homunculus (overrepresentation muscles of

the thumb, hand, face, tongue, distorted the thumb, hand, face, tongue, distorted somatotopic representation)somatotopic representation)

Afferents : S I, thalamic VL (cerebellum)Afferents : S I, thalamic VL (cerebellum) Efferents : basal ganglia, thalamus, (VL) RF, Efferents : basal ganglia, thalamus, (VL) RF,

superior colliculus, nc. ruber, RF, pontine ncc., superior colliculus, nc. ruber, RF, pontine ncc., spinal cordspinal cord

Control of distal musclesControl of distal muscles Damage produces paralysis of contralateral muscles Damage produces paralysis of contralateral muscles

(namely upper limb, tongue, facial muscles)(namely upper limb, tongue, facial muscles)

THE CORTICO-SPINAL

PATHWAY

PM

SMA

Premotor area, PMPremotor area, PM

Area 6Area 6 Somatotopic representation of the body Somatotopic representation of the body

musculature, less precisely organizedmusculature, less precisely organized Efferents – M I, basal ganglia, RF, Spinal Efferents – M I, basal ganglia, RF, Spinal

cord (influences paravertebral and proximal cord (influences paravertebral and proximal limb musculature)limb musculature)

Afferents – thalamic VA (basal ganglia), S I,Afferents – thalamic VA (basal ganglia), S I, Preparation to movePreparation to move

Supplementary motor areaSupplementary motor area

Area 6, medial surface of the hemisphereArea 6, medial surface of the hemisphere Somatotopic organization,less precisely Somatotopic organization,less precisely

organizedorganized Afferents – thalamic VA (basal ganglia), Afferents – thalamic VA (basal ganglia),

parietal cortexparietal cortex Efferents – MI, Basal ganglia, RF, Spinal cordEfferents – MI, Basal ganglia, RF, Spinal cord Area is involved in organizing and planning Area is involved in organizing and planning

the sequence of muscle activationthe sequence of muscle activation

Somatosensory area, S I, BA 3, 1, 2

Trigeminal (head) part of S I.

Sensory homunculus

Somatosensory area S ISomatosensory area S I

Postcentral gyrusPostcentral gyrus Areas 3a, 3b, 1, 2Areas 3a, 3b, 1, 2 Afferents : VPL, VPMAfferents : VPL, VPM Efferents : M I, thalamus (VPL, VPM), pontine ncc., Efferents : M I, thalamus (VPL, VPM), pontine ncc.,

nuclei of cranial nerves (V.), spinal cordnuclei of cranial nerves (V.), spinal cord 3a – signals from muscle spindles3a – signals from muscle spindles 3b – cutaneous receptors3b – cutaneous receptors 2 – joint receptors2 – joint receptors 1 – all modalities1 – all modalities

Feeling of elictricity

Sense of movement

Tingling

Homunculus

Distribution of signals from primary sensory area – to close associative area and finally to distant polysensory areas and to limbic cortex (memory, emotions)

LANGUAGE AREAS

Broca : patient losses the ability to speak, produces single words, or syllables. Understanding of language is preserved. Often combined with agraphia (area 44, 45)

Wernicke : sensory or receptive aphasia, spontaneous speech is fluent, but sounds are often put together into meaningless words – „ word salad „. Often combined with alexia – the inability to read (area 39, 40)

Auditory area

BA 41

Auditory areaAuditory area

Superior temporal gyrus (gyrus temporalis Superior temporal gyrus (gyrus temporalis transversus, Heschl gyrus)transversus, Heschl gyrus)

Area 41 = primary auditory area (A I)Area 41 = primary auditory area (A I) Areas 42, 21, 22 = associated auditory areas (A II)Areas 42, 21, 22 = associated auditory areas (A II) Afferent connections from auditory pathway Afferent connections from auditory pathway

(cochlear ganglion – cochlear nuclei- superior olive (cochlear ganglion – cochlear nuclei- superior olive – inferior colliculus – medial geniculate body – BA – inferior colliculus – medial geniculate body – BA 41)41)

Efferent connections ( A I – A II – temporal, Efferent connections ( A I – A II – temporal, parietal, frontal lobe, Broca area)parietal, frontal lobe, Broca area)

Auditory cortexAuditory cortex

Area 41Area 41 Afferents – auditory pathway (thalamic Afferents – auditory pathway (thalamic

medial geniculate body)medial geniculate body) Efferents – thalamus (medial geniculate Efferents – thalamus (medial geniculate

body), inferior colliculus, associative cortical body), inferior colliculus, associative cortical areas (what and where paths)areas (what and where paths)

Visual cortexVisual cortex

Area 17, granular cortexArea 17, granular cortex Afferents – visual pathway, thalamic lateral Afferents – visual pathway, thalamic lateral

geniculate body. Overrepresentation of geniculate body. Overrepresentation of central part of retina.central part of retina.

Efferents – thalamus (lateral geniculate Efferents – thalamus (lateral geniculate body), area 18, 19, parietal cortex, temporal body), area 18, 19, parietal cortex, temporal cortex.cortex.

Dorsal stream – parietal cortex (where : rods, Dorsal stream – parietal cortex (where : rods, periphery of retina, area 7)periphery of retina, area 7)

Ventral stream – temporal cortex (what- Ventral stream – temporal cortex (what- colors, form, surface : cones, central area of colors, form, surface : cones, central area of retina, area 37, inferior. temporal cortexretina, area 37, inferior. temporal cortex

Receptor mapping

Receptor concentration

fmol/mg protein

(K. Zilles et al. 2010)

Cortical commissural pathwaysCortical commissural pathways

Corpus callosum (250 – 300 millions fibers, Corpus callosum (250 – 300 millions fibers, originate in layer III, mainly excitatoryoriginate in layer III, mainly excitatory

Anterior commissure – pars olfactoria, pars Anterior commissure – pars olfactoria, pars interhemisphericainterhemispherica

Commisura fornicis (hippocampi)Commisura fornicis (hippocampi)

Corpus callosum –

transekce

Comissural

pathways

Associative pathwaysAssociative pathways

Short pathways – interconnect close Short pathways – interconnect close cortical areas ( area 6 with area 4)cortical areas ( area 6 with area 4)

Long pathways – interconnect distal Long pathways – interconnect distal cortical areas or lobes (occipital with cortical areas or lobes (occipital with frontal)frontal)

Cerebral cortexCerebral cortex

All mammals depend on it.All mammals depend on it.

A man without a cortex is almost A man without a cortex is almost vegetable, speechless, sightless, vegetable, speechless, sightless, senseless senseless (D. Hubel and T. Wiesel 1979).(D. Hubel and T. Wiesel 1979).

The cortex supports sensory perception, The cortex supports sensory perception, reasoning, planning and execution of reasoning, planning and execution of behaviors.behaviors.

Thank you !Thank you !

Neocortex - definiceNeocortex - definice

6 vrstev, 6 layers6 vrstev, 6 layers 10 – 20 miliard (bilions) neuronů10 – 20 miliard (bilions) neuronů 95 % povrchu hemisféry95 % povrchu hemisféry 95 % of the hemisphere surface95 % of the hemisphere surface

CALRETININ - IR

PV– ir, V - VI

ÚPRAVA HEMISFÉRYÚPRAVA HEMISFÉRY

Hemisféra – evertovanáHemisféra – evertovanáHemisféra - evaginovanáHemisféra - evaginovaná