MED 2013 Megighian

CORTECCIA CEREBRALE
MED 2013 Megighian
Saturday, October 5, 13
Corteccia
• Archicortex (3-4 strati)
• apprendimento-epilessia
• Paleocortex (3-4 strati)
• olfatto
• Neocortex
Saturday, October 5, 13
Neocortex
• 2600 cm2
• 30 x 109 neuroni
• miliardi di milioni di circuiti possibili
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Localizzazione vs generalizzazione
• Franz Gall
• J.Pierre Flourens
• 1861 Broca
• 1870 Fritz e Hitzig - stimolazione
• Jackson
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Lamine della corteccia
Fibre verticali
Fibre orizzontali
Fibre orizzontali
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Aree citoarchitettoniche
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Aree citoarchitettoniche
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Corteccia
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Neuroni piramidali
strati II-III e V-VI
gli asoni rappresentano il canale
efferente della corteccia
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Neuroni non piramidali
Saturday, October 5, 13
Sinapsi
• in un neurone piramidale ci sono circa
5000 sinapsi, 85% delle quali eccitatorie
• eccitatorie sui dendriti
• inibitorie sul corpo cellulare (circa il
15%)
Saturday, October 5, 13
Cellule dello strato 2/3 della corteccia
somatosensoriale
FS: fast spiking
RS: regular spiking
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Afferenze corticali
• Talamo-corticali
• specifiche
• diffuse
• Extra-talamiche
• Nuclei del rafe
• Locus coeruleus
• Telencefalo basale
• Area tegmentale ventrale
• Nucleo tubero mammillare
Saturday, October 5, 13
Nuclei del rafe
Serotoninergiche
ad azione modulatoria
sull’eccitabilità dei
neuroni corticali
Terminano in tutti gli
strati, ma principalmente
nel IV
Bersaglio dell’ecstasy
Saturday, October 5, 13
Locus coeruleus
Noradrenergici
terminano principalmente
negli strati V-VI e III e nella
corteccia motoria e
somatosensoriale
azione eccitatoria ed
inibitoria
Saturday, October 5, 13
Telencefalo basale
Colinergici
proiettano alla superfice
della corteccia
Le afferenze colinergiche
(rec M1) aumentano
l’eccitabilità dei neuroni
corticali agli input eccitatori
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Area tegmentale ventrale
Dopaminergici
corteccia motoria, cingolata,
prefrontale e frontale
Recettori D1 e D2
Sembra che la dopamina
liberata svolga un ruolo di
modulazione sulle afferenze
eccitatorie ai neuroni
piramidali
Saturday, October 5, 13
Nucleo tubero-mammillare
Istaminergici
ruolo modulatorio ancora
sconosciuto
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Azioni sui neuroni
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Efferenze corticali
Glutammato
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Colonne corticali
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FLY NEUROBIOLOGY LAB
A complicated circuit
Cortical column
Saturday, October 5, 13
About 104 neurons
22
FLY NEUROBIOLOGY LAB
Cortical column
About 104 neurons
Saturday, October 5, 13
23
Colonne corticali
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L’esperimento di Mountcastle
Downloaded from rstb.royalsocietypublishing.org on November 23, 2010
838
J. C. Horton and D. L. Adams
5.0
4.0
3.0
2.0
The cortical column at 50 years
1.0
0 mm
M8-P1 M13-P1 M14-P8
5
0
M4-P1 M21-P8
M9-P3
M19P1
2 1
2
1
2
1
3
skin deep
3
KEY
1
2
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4
PR
CS
5
3
CS
2
PCS
A
4
3
6
Figure 1. Mountcastle’s evidence for columnar segregation of
skin and deep receptors in areas 1, 2 and 3 of macaque
Rakic
Downloaded from rstb.royalsocietypublishing.org on November 23, 2010
and D. L. Adams
The cortical column at 50 years
rons display scatter in their preferred
often broadly tuned (Hetherington
Ringach et al. 2002). It has become
on columns are not discrete entities,
Hubel and Wiesel’s designation of 22
was arbitrary. Orientation tuning
asional fractures and singularities
h convinced Hubel and Wiesel that
tal—but in fact, optimal orientation
cross most of the cortical surface
sdel & Salama 1986). Therefore,
s classic model showing orientation
te slabs is misleading because the
rless in real life. The diagram is still
ecause it captures an early view of
mn systems in the primary visual
ganized.
rominent cell bands seen in Nissl
present individual orientation cole persuasive evidence that the adult
ed of discrete, elementary units
development. Across many species
ns, these bands have a width of
mm and contain a few hundred cells
80). Rakic (1971) has shown by
toradiography in foetal monkeys
ned for the neocortex are born in
Saturday, October 5, 13
Figure 5. Formation of radial minicolumns or ontogenetic
columns. (a) Progenitor cells in the ventricular zone (VZ) give
rise to progeny that migrate in succession along a glial scaffold
into the cortical plate (CP). These cells remain roughly
Colonne di dominanza
Downloaded from rstb.royalsocietypublishing.org on November 23, 2010
The cortical column at 50 years
Saturday, October 5, 13
Figure 3. Hubel and Wiesel’s ice cube tray model of the striate
cortex. In oblique microelectrode penetrations, they attributed the regular shift in orientation preference to an orderly
stacking of slab-like orientation columns. Orientation hypercolumns contained 18 discrete columns about 50 mm wide,
J. C. Ho
Figure 4. Ontogenetic colum
Saturday, October 5, 13
Corteccia acustica
712
V. B. Mountcastle
EE: excitatory omo and
controlateral
EI: excitatory omo and
inhibitory controlateral
Saturday, October 5, 13
Fig. 11 Left. Auditory sensory areas in the neocortex of the cat.
AAF anterior auditory field; A I
primary auditory field;
PAF posterior auditory field; VPAF ventral posterior
auditory field. These four fields are tonotopically organized. The
dark cross-hatched field is an auditory responsive area in which
no tonotopic organization has been defined; aes
anterior
ectosylvian sulcus; pes postgerior ectosylvian sulcus;
columns send and rec
azimuth location of sou
of space.
Every cellular study
monkey has provided
organization. Microelec
the pial surface encoun
II to layer VI that ha
binaural response pro
tangential direction, pa
successive blocks of ce
as the electrode passes
changes occur in step-w
may be as narrow as 10
A number of other f
the isofrequency bands
itself not uniform; it i
bands and somewhat
medial or lateral to th
Schreiner and Sutter,
Colonne corticali
Saturday, October 5, 13
Columns: Functional
Groupings of minicolumns seem to form the
physiologically observed functional columns.
known example is orientation columns in V1.
Best
They are significantly bigger than minicolumns,
typically around 0.3-0.5 mm.
Mountcastle’s summation:
“Cortical columns are formed by the binding together of many
minicolumns by common input and short range horizontal connections.
… The number of minicolumns per column varies … between 50 and
80. Long range intracortical projections link columns with similar
functional properties.” (p. 3)
Cells in a column ~ (80)(100) =
8000
Saturday, October 5, 13
Cortical minicolumns: Quantities
Saturday, October 5, 13
Cortical minicolumns: Quantities

Saturday, October 5, 13
Diameter of minicolumn: 30 microns
Cortical minicolumns: Quantities
Diameter of minicolumn: 30 microns
 Neurons per minicolumn: 75-110

Saturday, October 5, 13
Cortical minicolumns: Quantities
Diameter of minicolumn: 30 microns
 Neurons per minicolumn: 75-110
 Minicolumns/mm2 of cortical surface: 1413

Saturday, October 5, 13
Cortical minicolumns: Quantities
Diameter of minicolumn: 30 microns
 Neurons per minicolumn: 75-110
 Minicolumns/mm2 of cortical surface: 1413
 Minicolumns/cm2 of cortical surface: 141,300

Saturday, October 5, 13
Cortical minicolumns: Quantities
Diameter of minicolumn: 30 microns
 Neurons per minicolumn: 75-110
 Minicolumns/mm2 of cortical surface: 1413
 Minicolumns/cm2 of cortical surface: 141,300
 Approximate number of minicolumns in
Wernicke’s area: 2,825,000

Saturday, October 5, 13
More quantities
Number of neurons in cortex: 27.4 billion
 Number of minicolumns: 368 million
 Neurons per minicolumn: average 75-80
 Neurons beneath 1 mm2 of surface: 113,000

Mountcastle 96
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The cortical column
Saturday, October 5, 13
The cortical column

Saturday, October 5, 13
The neurons of a column are interconnected

∴ a whole column is active together

the column acts as a functional unit
The cortical column


The neurons of a column are interconnected

∴ a whole column is active together

the column acts as a functional unit
The neurons of a column are connected to:
adjacent columns – inhibitory and excitatory
connections
 distant columns, by means of long distance
excitatory connections (the white matter)

Saturday, October 5, 13
Simplified model of minicolumn
Cell Types
II
III
Pyramidal
Spiny
Stellate
IV
Inhibitory
Connections to
neighboring
columns not
shown
Saturday, October 5, 13
V
VI
Simplified model of minicolumn
II
III
Cell Types
Pyramidal
Spiny
Stellate
Inhibitory
Connections to
neighboring
columns not
shown
Saturday, October 5, 13
Thalamus
IV
V
VI
Simplified model of minicolumn
II
III
Cell Types
Pyramidal
Spiny
Stellate
Inhibitory
Connections to
neighboring
columns not
shown
Saturday, October 5, 13
Thalamus
IV
V
VI
Simplified model of minicolumn
II
III
Cell Types
Pyramidal
Spiny
Stellate
Inhibitory
Connections to
neighboring
columns not
shown
Saturday, October 5, 13
Thalamus
IV
V
VI
Simplified model of minicolumn
II
III
Cell Types
Pyramidal
Spiny
Stellate
Inhibitory
Connections to
neighboring
columns not
shown
Saturday, October 5, 13
Thalamus
IV
V
VI
Simplified model of minicolumn
Cell Types
Other
cortical
locations
II
III
Pyramidal
Spiny
Stellate
Inhibitory
Connections to
neighboring
columns not
shown
Saturday, October 5, 13
Thalamus
IV
V
VI
Simplified model of minicolumn
Other
cortical
locations
Cell Types
II
III
Pyramidal
Spiny
Stellate
Thalamus
Inhibitory
Connections to
neighboring
columns not
shown
Saturday, October 5, 13
IV
V
VI
Subcortical
locations
Simplified model of minicolumn
Other
cortical
locations
Cell Types
II
III
Pyramidal
Spiny
Stellate
Thalamus
Inhibitory
Connections to
neighboring
columns not
shown
Saturday, October 5, 13
IV
V
VI
Subcortical
locations
Colonne corticali
La corteccia e spessa circa 2 mm.
6 strati
Se si penetra perpendicolarmente alla superfice le cellule
rispondono principalmente allo stimolo da un occhio
(dominanza oculare).
Colonne di dominanza oculare.
Saturday, October 5, 13
FLY NEUROBIOLOGY LAB
A little bit complicated....
37
Saturday, October 5, 13
FLY NEUROBIOLOGY LAB
This small region
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Saturday, October 5, 13
FLY NEUROBIOLOGY LAB
A single neuron
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Inside the column
39
FLY NEUROBIOLOGY LAB
Layer four neuron in context
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Saturday, October 5, 13
FLY NEUROBIOLOGY LAB
The activity in the neocortex is tightly
controlled by inhibitory neurons. Shown here
are the inhibitory fibers in blue that wrap
around pyramidal neurons, in red, in order to
control their activity and prevent epilepsy.
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FLY NEUROBIOLOGY LAB
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FLY NEUROBIOLOGY LAB
.......all neural functions rely on:
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Saturday, October 5, 13
FLY NEUROBIOLOGY LAB
.......all neural functions rely on:
•
the ability of neurons to generate one/more action potentials
(bit of infomation)
42
Saturday, October 5, 13
FLY NEUROBIOLOGY LAB
.......all neural functions rely on:
•
the ability of neurons to generate one/more action potentials
(bit of infomation)
•
the possibility to send these bits (conduction along a short or
long axon)
42
Saturday, October 5, 13
FLY NEUROBIOLOGY LAB
.......all neural functions rely on:
•
the ability of neurons to generate one/more action potentials
(bit of infomation)
•
the possibility to send these bits (conduction along a short or
long axon)
•
the possibility to exchange these bits (synaptic function) and
integrate them
42
Saturday, October 5, 13
Colonne corticali
Saturday, October 5, 13
Circuiti intracorticali
Spessore delle linee
proporzionato alla forza
sinaptica della connessione.
Connessioni più numerose tra
i neuroni eccitatori, per cui,
un’afferenza talamica debole
può essere notevolmente
amplificata
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Aree primarie
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Midollo spinale
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Talamo
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Corteccia somestesica
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Mappe differenti
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Corteccia motoria
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Integrazione corticale
Aree associative unimodali
Aree associative multimodali
Flechsig (1900): Aree ineccitabili
maturazione tardiva della mielina
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Organizzazione delle connessioni
cortico-corticali
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Saturday, October 5, 13
NFT: ammassi
neurofibrillari
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NP:placche