Download THE CEREBRAL CORTEX

THE CEREBRAL CORTEX
Institute of Anatomy, 1st Medical Faculty
R. Druga
CORTEX CEREBRI
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Definice, Definition
Neocortex, Allocortex
Vývoj hemisféry a neokortexu
Development of the neocortex
Struktura neokortexu
Structure of the neocortex
Hlavní typy neuronů
Main types of neurons
DP =
dorsal
pallium
LGE=
lateral
ganglionic
eminence
MGE =
medial
ganglionic
eminence
MGE + LGE
NEOCORTEX
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Laminar pattern – 6 layers
10 – 20 billion neurons
95 % 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,
types of neurons
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Pyramidal
neurons
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Non-pyramidal
neurons
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Apical and basal
dendrites
Dendritic spines
Excitatory (glutamate)
Homogenous group
60 – 70 %
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Aspiny
Heterogenous group
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Inhibitory (GABA)
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30 – 40 %
Pyramidal
neurons
Layer V.
MI
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 layers
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I.. Molecular layer – local inhibitory interneurons
II. External granular – association neurons
III. External pyramidal – commissural neurons
IV. Internal granular – receives thalamocortical
projections
V. Internal pyramidal – projecting neurons (basal
ganglia, brain stem, spinal cord
VI. Multiform layer – corticothalamic neurons
V – basal ganglia
brain stem
spinal cord
VI - thalamus
Excitatory connections in the neocortex
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Layer 4 – termination of
thalamocortical projections
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Layer 4 – projects to layer 3
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Layer 3 – projects to layer 5
Association areas
Afferent neocortical connections
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Thalamic nuclei (thalamocortical fibers)
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Amygdala
Claustrum
Hypothalamus
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Nc. basalis (Meynert)-cholinergic system
Raphe nuclei (serotonin)
Locus coeruleus (noradrenalin)
Subst. Nigra (VTA) - dopamin
Efferent neocortical connections
(excitatory, glutamatergic)
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Thalamic nuclei
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Basal ganglia (striatum, amygdala, claustrum)
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Brain stem (pretectal area, tectum, nc. ruber, RF,
nuclei of cranial nerves, pontine ncc., nc. gracilis,
nc. cuneatus)
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Spinal cord ( corticospinal pathway, interneurons,
motoneurons)
Motor cortical area
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G. Fritsch and E. Hitzig (1870)
demonstrated that electrical
stimulation of the dog´s frontal lobe
results in contralateral muscular
contractions (movements)
Primary
motor area,
MI
Motor homunculus
Primary motor area M I
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Precentral gyrus, area 4
Part of the cortex from which movements are easily
produced by electrical stimulation
Motor homunculus (overrepresentation muscles of
the thumb, hand, face, tongue, distorted
somatotopic representation)
Afferents : S I, thalamic VL (cerebellum)
Efferents : basal ganglia, thalamus, (VL) RF,
superior colliculus, nc. ruber, RF, pontine ncc.,
spinal cord
Control of distal muscles
Damage produces paralysis of contralateral muscles
(namely upper limb, tongue, facial muscles)
THE
CORTICOSPINAL
PATHWAY
PM
SMA
Premotor area, PM
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Area 6
Somatotopic representation of the body
musculature, less precisely organized
Efferents – M I, basal ganglia, RF, Spinal
cord (influences paravertebral and proximal
limb musculature)
Afferents – thalamic VA (basal ganglia), S I,
Preparation to move
Supplementary motor area
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Area 6, medial surface of the hemisphere
Somatotopic organization,less precisely
organized
Afferents – thalamic VA (basal ganglia),
parietal cortex
Efferents – MI, Basal ganglia, RF, Spinal cord
Area is involved in organizing and planning
the sequence of muscle activation
Somatosensory area, S I, BA 3, 1, 2
Trigeminal (head)
part of S I.
Sensory
homunculus
Somatosensory area S I
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Postcentral gyrus
Areas 3a, 3b, 1, 2
Afferents : VPL, VPM
Efferents : M I, thalamus (VPL, VPM), pontine ncc.,
nuclei of cranial nerves (V.), spinal cord
3a – signals from muscle spindles
3b – cutaneous receptors
2 – joint receptors
1 – 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 area
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Superior temporal gyrus (gyrus temporalis
transversus, Heschl gyrus)
Area 41 = primary auditory area (A I)
Areas 42, 21, 22 = associated auditory areas (A II)
Afferent connections from auditory pathway
(cochlear ganglion – cochlear nuclei- superior olive
– inferior colliculus – medial geniculate body – BA
41)
Efferent connections ( A I – A II – temporal,
parietal, frontal lobe, Broca area)
Auditory cortex
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Area 41
Afferents – auditory pathway (thalamic
medial geniculate body)
Efferents – thalamus (medial geniculate
body), inferior colliculus, associative cortical
areas (what and where paths)
Visual cortex
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Area 17, granular cortex
Afferents – visual pathway, thalamic lateral
geniculate body. Overrepresentation of
central part of retina.
Efferents – thalamus (lateral geniculate
body), area 18, 19, parietal cortex, temporal
cortex.
Dorsal stream – parietal cortex (where : rods,
periphery of retina, area 7)
Ventral stream – temporal cortex (whatcolors, form, surface : cones, central area of
retina, area 37, inferior. temporal cortex
Receptor
mapping
Receptor
concentration
fmol/mg protein
(K. Zilles et al. 2010)
Cortical commissural pathways
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Corpus callosum (250 – 300 millions fibers,
originate in layer III, mainly excitatory
Anterior commissure – pars olfactoria, pars
interhemispherica
Commisura fornicis (hippocampi)
Corpus
callosum –
transekce
Comissural
pathways
Associative pathways
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Short pathways – interconnect close
cortical areas ( area 6 with area 4)
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Long pathways – interconnect distal
cortical areas or lobes (occipital with
frontal)
Cerebral cortex
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All mammals depend on it.
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A man without a cortex is almost
vegetable, speechless, sightless,
senseless (D. Hubel and T. Wiesel 1979).
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The cortex supports sensory perception,
reasoning, planning and execution of
behaviors.
Thank you !
Neocortex - definice
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6 vrstev, 6 layers
10 – 20 miliard (bilions) neuronů
95 % povrchu hemisféry
95 % of the hemisphere surface
CALRETININ - IR
PV– ir, V - VI
ÚPRAVA HEMISFÉRY
Hemisféra – evertovaná
Hemisféra - evaginovaná