THE CEREBRAL THE CEREBRAL CORTEXCORTEX

Institute of Anatomy, 2nd Medical Institute of Anatomy, 2nd Medical FacultyFaculty

R. DrugaR. Druga

NEOCORTEXNEOCORTEX

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

NEOCORTEX,NEOCORTEX, types of neuronstypes of neurons

Pyramidal Pyramidal neuronsneurons

Apical and basal Apical and basal dendritesdendrites

Dendritic spinesDendritic spines Excitatory Excitatory

(glutamate)(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

Projection neurons, excitatory, glutamate

Long axonsLocal circuit neurons, inhibitory, GABA

Interneurons, short axons

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

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 V. Internal pyramidal – projecting neurons

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

K.Brodmann, 1907, 1911

11 regions

52 areas

Association areas

Afferent neocortical connectionsAfferent neocortical connections

Thalamic nucleiThalamic nuclei (thalamocortical fibers) (thalamocortical fibers) AmygdalaAmygdala ClaustrumClaustrum Nc. basalis (Meynert)-cholinergic systemNc. basalis (Meynert)-cholinergic system HypothalamusHypothalamus Raphe nuclei (serotonin)Raphe nuclei (serotonin) Locus coeruleus (noradrenalin)Locus coeruleus (noradrenalin) Subst. Nigra (VTA) - dopaminSubst. Nigra (VTA) - dopamin

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

Efferent neocortical Efferent neocortical connectionsconnections

Thalamic nucleiThalamic nuclei

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

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

Spinal cord ( corticospinal pathway, Spinal cord ( corticospinal pathway, interneurons, motoneurons)interneurons, 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 stimulation of the dog´s frontal lobe results in contralateral lobe results in contralateral muscular contractions muscular contractions (movements)(movements)

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

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

colliculus, nc. ruber, RF, pontine ncc., spinal cortcolliculus, nc. ruber, RF, pontine ncc., spinal cort 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)

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, Efferents – M I, basal ganglia, RF,

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

Afferents – thalamic VA (basal ganglia), Afferents – thalamic VA (basal ganglia), S I,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 Efferents – MI, Basal ganglia, RF, Spinal

cordcord Area is involved in organizing and Area is involved in organizing and

planning the sequence of muscle planning the sequence of muscle activationactivation

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 Efferents : M I, thalamus (VPL, VPM), pontine

ncc., nuclei of cranial nerves (V.), spinal cordncc., nuclei 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

Sensory homunculus

LANGUAGE AREAS

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

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.

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

Visual cortexVisual cortex

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

lateral geniculate bodylateral geniculate body Efferents – thalamus (lateral geniculate Efferents – thalamus (lateral geniculate

body), area 18, 19, parietal cortex, body), area 18, 19, parietal cortex, temporal cortex.temporal cortex.

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

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

Corpus callosum –

transekce

Cerebral cortexCerebral cortex

All mammals depend on itAll 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 The cortex supports sensory perception, reasoning, planning and perception, reasoning, planning and execution of behaviorsexecution of behaviors