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Architecture of the Cerebral Cortex
Two methods for studying the
architecture of the cerebral cortex.
The cytoarchitecture of the cortex
is revealed by treating the cortex
with a method that stains the cells'
bodies or axions, thus showing
how they are arranged in layers.
(a) The cytoarchitecture of the
motor cortex.
(b) The cytoarchitecture of the
primary visual cortex, area V1
(c) The myeloarchitecture of the
cortex (for V1), is revealed by
staining the cortex by a
method which shows the
myelin sheaths covering the
nerve fibers.
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(Zeki, 1993)
nThe layers of the cerebral cortex.
nThe three vertical columns
represent the disposition of
cellular elements as revealed by
the staining techniques of Golgi
(impregnating whole neurones),
Nissl (staining cell bodies) and
We i ge r t (staining nerve fibres).
I. Molecular Layer
II. External Granular Layer
III. External Pyramidal Layer
IV. Internal Granular Layer
V. Internal Pyramidal Layer
VI. Polymorphic Layer
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IV
V
VI
III
II
I
1. Pyramidal Cell
2. Fusiform Cell (modified pyramidal)
3. Granular (Stellate) Cell
4. basket cell
5. double bouquet cell
6. chandlier cell
7. neurogliform cell
8. Horizontal Cell of Cajal
9. Cells of Martinotti
a: axon
Cerebral Cortex
(Kolb & Whishaw, 2009)
Cortex (Gray matter layers)
• Molecular layer
• External granular layer
Association & Commissure Input
• External pyramidal cell layer
Association & Commissure output
• Internal granular layer
Thalamic Projection (input)
• Internal pyramidal cell layer
Corticofugal Projection
• Multiform cell layer
Corticothalamic Projection
Medulla (White matter)
Skull & Meninges
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nThe neocortex is organized into areas, layers, and columns
populated by a great diversity of excitatory and inhibitory
neuronal subtypes.
nAbout two-thirds of the neurons in the cortex are pyramidal
cells or excitatory, projection neurons, so called because their
cell bodies are shaped like pyramids. These tend to have a
long axon and extensive dendrites.
nThe remainder of the neurons are interneurons, and non-
pyramidal. Non-pyramidal cells (mainly inhibitory) are often
given names which reflect their appearance.
nMultipolar cells or Stellate cells are relatively small, multipolar,
can be spiny or nonspiny, and form about one third of the total
neuronal population of the cortex.
nChandelier and basket cells are named after their
arrangement and appearance.
nThe neurotransmitter used by pyramidal cells is either glutamate or
aspartate (excitatory). In spiny stellate cells it is glutamate (excitatory),
while in most nonspiny stellate cells it is GABA (inhibitory).
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nGolgi stained neurons in different layers of cerebral cortex: a) Layer II/III pyramidal
cell; b) layer IV spiny stellate cell.
nDendritic spines are visible on branching dendrites as clusters of tiny thorn-like
bristles.
(Koenigshofer, 2011)
The Pyramidal (projection) Neuron
nAs it is shown in picture ‘A’ drawn by Ramon y Cajal, the cerebral cortex is
rich in pyramidal neurons of different sizes.
nFigure ‘B’ depicts a golgi-impregnated pyramidal neuron . Note, the
ramification of the basal and apical dendrites .
nFigure ‘C’ illustrates the main structural domains of the spiny pyramidal
neuron.
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Myeloarchitecture map
nElliot Smith’s (1907) ‘myeloarchitectonic’ map of the human cerebral cortex.
na, b Architectonic map, based entirely on the study of fresh, unstained macroscopic
sections of the cerebral cortex.
nc Pictures showing 7 of the about 50 areas, distinguished by Elliot Smith.
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(from Nieuwenhuys, 2013)
Brodmann (1868-1918)
nKorbinian Brodmann (1868-1918) (left), the German neuro-anatomist whose work was to
have a lasting influence in brain studies, and his cytoarchitectonic chart of the brain
(right).
nHe defined 52 distinct regions, known as Brodmann areas, based on their cytoarchitectonic
(histological) characteristics. Brodmann settled on as effective a terminology for the
cortical areas as any ever invented – he numbered them according o the sequence in which
he studied them.
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(reproduced from Polyak, 1957)
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n
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A, lateral view;
B, medial view,
C, inferior view
D, lateral surface
of the hemisphere
Cytoarchitectural zones of
the human cerebral cortex,
according to Brodmann (1914).
AB
C
D
(from Brodmann , 1914)
nNissl-stained section of areas 17–19
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(from Sarkissov et al. 1955)
nAlternate cytoarchitecture map of neocortex: von Economo and Koskinas (1925).
nAt the two extremes are the heterotypical cortices: agranular cortex (1) dominated by
large pyramidal cells, and granular cortex (5, koniocortex) dominated by small cells.
Areas with intermediate structures in which six layers can be discerned more clearly
are homotypical and were divided into three types by von Economo: 2, frontal type; 3,
parietal type; 4, polar type;
nB, Distribution of heterotypical cortex. The lateral view, above, is drawn as though the
lateral sulcus had been pried open, exposing the insula. Agranular cortex (green) is
found primarily in motor areas, granular cortex (blue) primarily in sensory areas
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(modified from von Economo, 1929)
nSummary diagram of primary and unimodal association areas. The lateral view is drawn as though
the lateral sulcus had been pried open, exposing the insula.
nVisual association cortex is particularly extensive in primate brains, occupying not only most of the
occipital lobe but also much of the temporal lobe. Many of these various functional areas are
associated with one or more of Brodmann’s anatomically defined areas, although sometimes the
correspondence is only approximate; commonly used Brodmann numbers are indicated in
parentheses (area 2 usually does not extend onto the medial surface of the hemisphere).
nA1, M1, S1, V1, primary auditory, motor, somatosensory, and visual cortex; S2, second
somatosensory area; SMA, supplementary motor area.
nGustatory and Visceral Cortex in middle and posterior Insula.
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(modified from von Economo, 1929)
Significant ALE localization of human olfactory cortex
nLocalization in MNI
space (left side of
the brain on left
side of the picture).
nNumbers above
brain slices
indicate
stereotactic
coordinates in axial
orientation and
blue lines indicates
location of
displayed slices.
nActivation seen in
PirF, PirT, aI, pI,
OFC, FMG, ACG,
SFG, MFG.
(Seubert et al., 2013)
nLocalization of the significant activation
likelihood estimation (ALE) in the
bilateral insulae by taste stimulations
overlaid onto a standard template
(Colin27_T1_seg_MNI.nii) in Montreal
Neurological Institute (MNI) space.
nBilateral activation patterns were
relatively symmetrical and focused on
the anteroventral and middle dorsal
parts. The map was generated using data
from 238 individuals.
nNote: Activation was also
observed in the Thalamus,
Caudate, Pre-/Postcentral Gyrus,
And Right Hippocampus (not
shown).
(Yeung et al., 2017)
Basic taste processing recruits bilateral anteroventral
and middle dorsal insulae
nReceptor-, cyto-, and
myeloarchitecture of the
human primary
somatosensory cortex
(S1, area 3b).
nRoman and Arabic
numerals indicate cyto-
and myeloarchitectonic
layers, respectively.
(Palomero-Gallagher & Zilles, 2019)
Receptor-architecture
of human cortex.
nMyelinated fibre bundles and
cell soma columns in the same
region (planum temporale) of a
16-year-old male cortex.
nAlthough these are not serial
sections, the correlation between
myelin bundles
(myeloarchitecture) and
cell arrays (cytoarchitecture) is
clear.
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(Buxhoeveden & Casanova, 2002)
↑skull
↑skull ↓white matter
↓white matter
Modularity in neocortical circuitry
nThe Neocortex has minicolumns spaced about 1/30 mm apart, thanks to a tendency of
dendrites to bundle together.
nThere are about 100-200 neurons in such a minicolumn, and they seem likely to all be
interested in similar inputs (the orientation columns of visual cortex are the classic
example).
nSuperficial pyramidal cell axons tend to give off terminal clusters about every 0.500
mm., thus, each column knows what neighboring columns are doing.
nEach column functions by fine tuning it's activity on the basis of it's current input from
the deep layers and it's neighbor's activity (from the superficial layers).
(Calvin, 1990)
The `decline' of the single cell and the rise of complex plasticity
nA networking concept of the brain has slowly replaced views
singling out the neurone as the functional unit of the brain (Douglas
and Martin, 1991).
nArguably, the loss of single cell autonomy is more evident in the
neocortex than anywhere else, contributing to the theory of a
distributed function system (Mountcastle, 1997).
nThe output of a minicolumn may resemble that of a single, very
complex (usually projection) neurone, or that of a tightly knit group
of neurones in phylogenetically older parts of the nervous system.
nThe column contains concentrated circuitry in highly localized units
(an integrated circuit), diminishing the autonomy of single cells
within it, and decreasing connectivity costs.
nThe minicolumn is now seen as the most basic and consistent
template by which the neocortex organizes its neurones, pathways
and intrinsic circuits.
(Buxhoeveden & Casanova, 2002)
Basil Ganglia
Caudate in RED, Putamen in BLUE, Amygdala in YELLOW
Hippocampus & Fornix 112
Hippocampus in RED, fornix in violet, are critical for episodic memory.
The hippocampus is often said
to have three portions:
ahead (blue), a body (red), and
atail (green), which are
specialized for emotional,
cognitive, and spatial memory.
This is not universally accepted.
+Hippocampus 113
(above) Ammon: Egyptian god
with ram's horns.
CA = Cornu Amonis
(Ammon's horn)
(Below) human hippocampus
next to a specimen of
hippocampus leria
Entorhinal Cortex (BA 28)
Neuroimaging Techniques
nThe use of newly developed technologies that allow researchers
to study the structure and function of the brain by tracking
indicators of brain activity
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'Talairach and Tournoux' coordinate system
nThe 'Talairach' coordinate system is used to define neuroanatomical
locations of normalized images.
nThe 'Talairach' coordinate system specifies locations relative to their
distance from the anterior commisure (AC). The AC is a small but easy to
spot region, making it an ideal origin for the coordinate system.
nEach location is described by three numbers, each describing the distance in
millimeters from the AC: X is the left/right dimension, Y is the
posterior/anterior dimension, and Z is the ventral/dorsal dimension.
•The position 0x0x0 is precisely at the AC,
while -32x21x10 is left (32mm), anterior
(21mm) and dorsal (10mm) from the AC.
Based on post mortem evaluation of single patient neurology and cytology.
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nStandard brain coordinate
system.
(A)The standard MNI brain template
in MNI coordinate space.
(B)Spatial normalization of a
subject’s brain to the MNI
space. Any position in the
individual brain (an example is
marked with an asterisk in the
figure), can be described by sets
of MNI coordinate values after
being spatially normalized to the
standard brain template.
The orientation of axial plane lies immediately dorsal
to the ac and ventral the posterior commissure.
