THE CEREBRAL CORTEX
Institute of Anatomy, 2nd Medical
Faculty
R. Druga
NEOCORTEX
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Laminar pattern – 6 layers
10 – 20 billion neurons
95 % surface of the hemisphere
NEOCORTEX,
types of neurons
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Pyramidal
neurons
Apical and basal
dendrites
Dendritic spines
Excitatory (glutamate)
Homogenous group
60 – 70 %
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Non-pyramidal
neurons
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Aspiny
Heterogenous group
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Inhibitory (GABA)
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30 – 40 %
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Pyramidal
neurons
Layer V.
MI
Golgi
impregnation
Projection neurons, excitatory, glutamate
Long axons
Local 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 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
K.Brodmann, 1907,
1911
11 regions
52 areas
Association areas
Afferent neocortical connections
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Thalamic nuclei (thalamocortical fibers)
Amygdala
Claustrum
Nc. basalis (Meynert)-cholinergic system
Hypothalamus
Raphe nuclei (serotonin)
Locus coeruleus (noradrenalin)
Subst. Nigra (VTA) - dopamin
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
Efferent neocortical connections
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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)
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 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, somatotopic
representation)
Afferents : S I, thalamic VL
Efferents : basal ganglia, thalamus, (VL) RF,
superior colliculus, nc. ruber, RF, pontine ncc.,
spinal cort
Control of distal muscles
Damage produces paralysis of contralateral muscles
(namely upper limb, tongue, facial muscles)
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
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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
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 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
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 : cones, central area of retina,
area 37, inferior. temporal cortex
Corpus
callosum –
transekce
Cerebral cortex
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All mammals depend on it
A man without a cortex is almost
vegetable, speechless, sightless,
senseless (D. Hubel and T. Wiesel 1979).
The cortex supports sensory perception,
reasoning, planning and execution of
behaviors