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s
Il existe unvieux dbat en
neurosciencessur les
contributionsrelatives duthalamus et du
cortex dans leprocessus qui
produitl activitcrbraleprsente dans
le cortexsensoriel
primaire
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es deux positions dans ce dbat A un extrme se
trouve un modlede type -feed
forward o lesconnexionscorticales
locales ne jouentpas un rle
dominant etl activit est
dictemajoritairementpar les entresthalamiques( ).Hubel et Weisel
A l autre extrmese trouve le
point de vueselon lequel
l informationvenant du
thalamus ne faitque
perturber l activit spontane dj
prsente dans unrseau cortical
fortement.interconnect
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A Lejeune 3
Perceptron dpourvu d activitspontane
Activit spontane dj prsentedans un rseau cortical fortement
interconnect
es deux positions dans ce dbat
Schematic diagram of circuitry for the lateral.geniculate nucleus The inputs to relay cells
are shown along with the relevantneurotransmitters and postsynaptic receptors
( ) :ionotropic and metabotropic AbbreviationsLGN , ;lateral geniculate nucleus BRF , brainstem;reticular formation TRN , thalamic reticular
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a position de la poule a position de l oeuf
tendu l ensemble des sciences( , )ognitives Varela 1992
Le mondeextrieur
comporte desrgles fixes; ilprcde limagequil projette sur
le systmecognitif dont latche est desaisir le monde
de manireapproprie (que
Le systmecognitif cre son
propre monde, ettoute sonapparentesolidit repose
sur les loisinternes delorganisme
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Prsentation dun article auprofesseur Thomas Gisiger
dans le cadre du cours
Somatosensory CorticothalamicProjections: Distinguishing
Drivers from Modulators
par
Iva Reichova et S. MurraySherman
Journal of Neurophysiology, 2004
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IntroductionRappel: les rcepteurs ioniques et mtabotropiquesRappel: les effets inhibiteur ou exitant
The ion channel is regulated by a ligand and is usually veryselective to one or more ions likeNa+,K+,Ca +2 , or Cl-. Suchreceptors located at synapses convert the chemical signal of
presynaptically released neurotransmitter directly and veryquickly into a postsynaptic .electrical signal
n contrast to the latter ,etabotropic eceptors do notorm an on channelpore ; ,atherhey are indirectly linked with-on channels on the plasmaembrane of the cell throughignal transduction ,mechanismsoften proteins . ,ence they aretype of-protein coupled receptor.
thers are yrosine kinases orguanylylcyclasereceptors .
F t t
http://en.wikipedia.org/w/index.php?title=Guanylyl_cyclase_receptors&action=edit&redlink=1http://en.wikipedia.org/wiki/Ion_channelhttp://en.wikipedia.org/wiki/Ligand_(biochemistry)http://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Potassiumhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Chloridehttp://en.wikipedia.org/wiki/Synapsehttp://en.wikipedia.org/wiki/Presynaptichttp://en.wikipedia.org/wiki/Postsynaptichttp://en.wikipedia.org/wiki/Ion_channelhttp://en.wikipedia.org/wiki/Porehttp://en.wikipedia.org/wiki/Signal_transductionhttp://en.wikipedia.org/wiki/G_proteinhttp://en.wikipedia.org/wiki/G_proteinhttp://en.wikipedia.org/wiki/G_protein-coupled_receptorhttp://en.wikipedia.org/wiki/G_protein-coupled_receptorhttp://en.wikipedia.org/wiki/Receptor_tyrosine_kinasehttp://en.wikipedia.org/w/index.php?title=Guanylyl_cyclase_receptors&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Guanylyl_cyclase_receptors&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Guanylyl_cyclase_receptors&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Guanylyl_cyclase_receptors&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Guanylyl_cyclase_receptors&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Guanylyl_cyclase_receptors&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Guanylyl_cyclase_receptors&action=edit&redlink=1http://en.wikipedia.org/wiki/Receptor_tyrosine_kinasehttp://en.wikipedia.org/wiki/Receptor_tyrosine_kinasehttp://en.wikipedia.org/wiki/G_protein-coupled_receptorhttp://en.wikipedia.org/wiki/G_proteinhttp://en.wikipedia.org/wiki/Signal_transductionhttp://en.wikipedia.org/wiki/Porehttp://en.wikipedia.org/wiki/Ion_channelhttp://en.wikipedia.org/wiki/Postsynaptichttp://en.wikipedia.org/wiki/Presynaptichttp://en.wikipedia.org/wiki/Synapsehttp://en.wikipedia.org/wiki/Chloridehttp://en.wikipedia.org/wiki/Chloridehttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Potassiumhttp://en.wikipedia.org/wiki/Potassiumhttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Ligand_(biochemistry)http://en.wikipedia.org/wiki/Ion_channel -
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( )A
( , )Reichova et Sherman 2004
L aire corticale 1tant une aire
,sensorielle primaire sacouche 4
est la cible deprojections du noyau
sensoriel thalamique A(le CGL par ).exemple
,Les aires corticales 12 et 3 sont aussi
relies par desprojections -cortico corticales
-liant leurs couches 1 3.et 6
Le noyau thalamique Areoit aussi des
projections en retour
de l aire ,corticale 1 qui sont
issues de sa couche 6
Firsttransmission to
cortex from the=periphery DRIVER
:GN Lateral Geniculate Nucleus:P Ventral Posterior Nucleus
Firsttransmission to
cortex from the=periphery DRIV
ER
Drivers et ModulatorsF rst transm ss onto cortex from the
periphery=DRIVER
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( )A ( )B
Les inputscholinergiques
du niveau 5
Le noyau B reprsentepar exemple
une partie du.pulvinar
l ne reoit aucune nformationsensorielle , mais il est la ciblede connexions projetes
par les neurones descouches 4 et 5 de
.l aire corticale 1 Il est aussi connect
,avec l aire 2projetant sur sa
Drivers et Modulators
DRIVER
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n veau eslimite lamorphologie(Flowery) Li et al.(2003)
e but de cetteecherche estapprofondir cette.ypothse de Li et al( ) 003 qui distinguentur des basesorphologiques deuxroupes d inputs sur leateral Posterior( ):halamus LPT- n groupe avec ynaptic depression;nhibiteur- - n groupe avec ynaptic acilitationtimulation sansoutefois identifiera source corticale( )iveau 5 OU 6?
Drivers et Modulators
n va donc activer les axones des couches 5 et 6 sur uneouche thalamocorticale et enregistrer les rponses sur le( )oyau ventral postrieur 1er ordre FO et le noyau mdial( )ostrieur HO
Fi d l h fi i i
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Design de larecherche
Retinogeniculate activation evoked large, all-or-none excitatory postsynaptic potentials(EPSPs) that showed paired-pulse depression antagonized by N-methyl-D-aspartate (NMDA)and AMPA receptor blockers butwith no sign of a metabotropic glutamate receptor (mGluR)component.Corticogeniculate activation evoked small, graded EPSPs showing paired-pulsefacilitation, and the EPSPs showed both NMDA and AMPA receptor component plus anmGluR1 component
n vestig ate syna p tic p rop erties ofo rtico th a la m ic in p u ts8 ce lls
comparaison avec
-First order relays represent the first transmissionto cortex of particular type of information from the periph
-Higher order relays serve to transmit information between- -cortical areas via a cortico thalamo cortical route
cellsHOst O
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methods
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thalamocorticalslice preparationasseen in recordingchamber
A: lower-power view ofslice. Barrel cortex (BC)can be clearly identifiedaswell as the externaland internal capsules(EC, IC) andthe ventral posterior(medial and lateral) andposteriormedial nuclei(VP,POm). The stimulating
electrode isshown in the barrelcortex and recordingelectrodes arelocated in the ventralposterior and posterior
medialnuclei.
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Recordings from geniculate cells wereperformed under visual control.
Electrical stimulation was performed inthe
optic tract, which lies ventral to the
lateral geniculate nucleus, and in theoptic radiations, which lie dorsal.
Stimulation andrecording (2)
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Rappel:A receptorantagonist is
1] In pharmacology,antagonists have affinitybut no efficacy for their
cognate receptors, andbinding will disrupt theinteraction and inhibit thefunction of an agonist orinverse agonist at receptors.Antagonists mediate theireffects by binding to theactive site or to allostericsites on receptors, or theymay interact at uniquebinding sites not normallyinvolved in the biological
'
A receptorantagonist is atype ofreceptorligand ordrug that doesnot provoke abiologicalresponse itself
upon binding toa receptor, butblocks ordampens agonist-mediatedresponses.[
D e s a n ta g o n iste s so n t u tilis s su r le s( ),rcep teu rs G A B A a et b
, ,A M PA m G lu R m G lu R 5
http://smb//tmp/sv8h6.tmp/#cite_note-pharmguide-0http://en.wikipedia.org/wiki/Pharmacologyhttp://en.wikipedia.org/wiki/Dissociation_constant%23Protein-Ligand_bindinghttp://en.wikipedia.org/wiki/Efficacy%23Pharmacologyhttp://en.wikipedia.org/wiki/Agonisthttp://en.wikipedia.org/wiki/Inverse_agonisthttp://en.wikipedia.org/wiki/Receptor_(biochemistry)http://en.wikipedia.org/wiki/Ligand_(biochemistry)http://en.wikipedia.org/wiki/Drughttp://en.wikipedia.org/wiki/Receptor_(biochemistry)http://en.wikipedia.org/wiki/Agonisthttp://smb//tmp/sv8h6.tmp/#cite_note-pharmguide-0http://smb//tmp/sv8h6.tmp/#cite_note-pharmguide-0http://en.wikipedia.org/wiki/Agonisthttp://en.wikipedia.org/wiki/Receptor_(biochemistry)http://en.wikipedia.org/wiki/Drughttp://en.wikipedia.org/wiki/Ligand_(biochemistry)http://en.wikipedia.org/wiki/Receptor_(biochemistry)http://en.wikipedia.org/wiki/Inverse_agonisthttp://en.wikipedia.org/wiki/Agonisthttp://en.wikipedia.org/wiki/Efficacy%23Pharmacologyhttp://en.wikipedia.org/wiki/Dissociation_constant%23Protein-Ligand_bindinghttp://en.wikipedia.org/wiki/Pharmacologyhttp://smb//tmp/sv8h6.tmp/#cite_note-pharmguide-0http://smb//tmp/sv8h6.tmp/#cite_note-pharmguide-0 -
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. Antagonist activitymay be reversible orirreversibledepending on thelongevity of the
antagonistreceptorcomplex, which, inturn, depends on thenature of antagonistreceptor binding.
The majority of drugantagonists achievetheir potency bycompeting withendogenous ligandsor substrates atstructurally-defined
A receptorantagonist is(2)
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Paired-pulse facilitation:definition
When a presynaptic neuron receivestwo stimuli in rapid succession, thepostsynaptic response will commonly
be larger for the second than for thefirst pulse a phenomenon known aspaired-pulse facilitation (PPF). Now
here's an easy question for everyneurophysiologist: what is themechanism responsible for PPF?Although most people will quicklypoint in the direction of 'residual
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Paired-pulse depression
When two depolarizing stimuli aredelivered in close succession to a
group of axons, their averageresponse to the second one issometimes smaller than to thefirst. This form of short-term
plasticity is more common atinhibitory than at excitatorysynapses.
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resultsEPSPs showing the modulator signature :paired-pulsefacilitation, graded response, mGluR component; the driversignature : paired-pulse depression, all-or none response,no mGluR component
th l ti l
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thalamocorticalslice preparationasseen in recordingchamber
A: lower-power view ofslice. Barrel cortex (BC)can be clearly identifiedaswell as the externaland internal capsules
(EC, IC) andthe ventral posterior(medial and lateral) andposteriormedial nuclei(VP,POm). The stimulating
electrode isshown in the barrelcortex and recordingelectrodes arelocated in the ventralposterior and posterior
medialnuclei.
To iso la te excita to ry p o stsy n a p tic p o te n tia ls( ) ,EPSPs in allrecordings we used GABA receptor
a n ta g o n ists
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ynap c npu s o ce s othe lateral geniculate
nucleus
To h e lp e sta b lish syn a p tic p ro p e rtie s o fd rive rs a n d co n tra st th e m w ith la ye r 6
,m o d u la to r p ro p e rtie s w ith o u r te ch n iq u e s w efirst re co rd e d fro m th e la te ra lg e n icu la te
.n u cle u s
: ;rat G ran seth an d Lind stro m 20 03 Turne r; :a n d S a lt 1 9 9 8 m o u se C h e n a n d R e g e h r
; .2 0 0 0 C h e n e t a l ; :20 02 gu ine a pig; :M cCo rm ick and Von K rosigk 1 99 2 cat
;Lind stro m an d W ro be l1 9 9 0 also ou r ow nu n p u b lishe d o b serva tion s
W e th u s e le ctrica lly stim u la te dth e o p tic tra ct an d ra d ia tio n s w h ile
re co rd in g fro m.g e n icu la te re la y ce lls
d d l t i sh o in g e cita to r p o sts n a p tic p o te n tia ls
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In this and all subsequentfiguresshowing evoked EPSPs,inhibition was blocked byapplication of SR95531 (aGABAA antagonist, 20 M) and
CGP46381 (a GABABantagonist, 40 M). A, i and ii: large EPSP
showing paired-pulsedepression evokedfrom retinogeniculate
stimulation (Ai)contrasts with smallEPSP showing paired-pulse facilitationevoked fromcorticogeniculate
stimulation (Aii). B i and ii: increasin
. .and modulators inthe mouse lateralgeniculatenucleus
sh o w in g excita to ry p o stsyn a p tic p o te n tia ls( )EPSPs evoked from stimulation of
re tin o g e n icu la te a ffe re n ts via th e o p tic tra ct( )Ai Di or corticogeniculate afferents via
(the optic radiation )Aii Dii
d d l t i sh o w in g excita to ry p o stsyn a p tic p o te n tia ls
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C, i and ii: EPSPs evokedby low-frequencystimulation (10 Hz) fromboth sites completelyblocked by AMPA and N-methyl-D-aspartate (NMDA)receptor antagonists (DNQX,50 M, and MK-801, 50 M,respectively).
D, i and ii: high-frequencystimulation (HFS, 110 Hz)of retinogeniculateafferents evokes no
further response withcontinued application ofAMPA and NMDAantagonists (Di).
Low-frequency stimulation(LFS, 10 Hz) ofcorticogeniculate afferents in
the presence of continuedAMPA and NMDA antagonists
. .and modulators inthe mouse lateralgeniculatenucleus
sh o w in g excita to ry p o stsyn a p tic p o te n tia ls( )EPSPs evoked from stimulation of
re tin o g e n icu la te a ffe re n ts via th e o p tic tra ct( )Ai Di or corticogeniculate afferents via the
(optic radiation )Aii Dii
Synaptic inputs to cells of the
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Synaptic inputs to cells of theventral posterior medial and
posterior medial nuclei
orticothalamic connections in the slice ynaptic properties of layer 6 inputs to
( he ventral posterior medial nucleus VP1st )rder ortical inputs to the posterior medial
We focused n two thalamic relays .One is ( he ventral posterior VP 1st )rderedial nucleus, ,which is a first order relay like
,the lateral geniculate nucleus and thus receivesonly a layer 6 input from cortex. The other is the( )osterior medial POm High Order nucleus ,
- ,which is mostly a higher order relay like the,pulvinar and thusreceives inputs from both layer 5.and layer 6 of cortex
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connections in the
sliceEPSPs showing the modulator signature :paired-pulsefacilitation, graded response, mGluR component; the driversignature : paired-pulse depression, all-or none response,no mGluR component
corticothalamic
C o rtico th a la m ic a xo n s fro m la ye rs 5
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corticothalamicpathway
A: injection site(arrow) in BC.Also visible is theIC. The lettered
boxes refer to thehigher power viewsin BD.B: labeled axonsrunning between
externalandinternal capsules.C: terminalboutons of
corticalfibers inthalamic reticular
C o rtico th a la m ic a xo n s fro m la ye rs 5a n d 6 a re o rth o g ra d e ly la b e le d b y
b io cytin io n to p h o re sis in to th e b a rre lcortex
corticothalamic
C o rtico th a la m ic a xo n s fro m la ye rs 5
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corticothalamicpathway
Many axons ramify inthe thalamic reticularand ventral posteriornuclei and terminatethere, but a few
continue further to theposterior medialnucleus.D: terminalboutonsof cortical axons inthe ventral posteriormedial nucleus andPOm.Several of the largerboutons in theposterior medial
nucleus are circled.
C o rtico th a la m ic a xo n s fro m la ye rs 5a n d 6 a re o rth o g ra d e ly la b e le d b y
b io cytin io n to p h o re sis in to th e b a rre lcortex
layer 6 inputs to the
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layer 6 inputs to theventral posterior (VP 1st
Order) medial nucleusEPSPs showing the modulator signature :paired-pulsefacilitation, graded response, mGluR component; the driversignature : paired-pulse depression, all-or none response,no mGluR component
subcortical
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subcorticalstimulation in a cellin the ventralposterior medialnucleus
The EPSPs evokedby low frequency
stimulation (LFS 400 A,14 Hz for 800 ms)are blocked withapplication of MK-801
and DNQX(top). With theseantagonists present,high-frequencystimulation (HFS, 125Hz for 800 ms) evoked
a sustainedEPSP (middle) that isblocked by the mGluR1antagonist, LY367385(50 M, bottom).The line below the
trace marks the time ofthe dru a lication.
: e x a m p le o f e v o k e d E P S P s . : -p a ire d p u ls e a cilita tio n a n d g ra d e de sp o n se o f E P S P s : e v id e n c e f a n m G lu R 1 co m p o n e n t. : .c o n tro l ( )Y 3 6 7 3 8 5 5 0 M a p p lie d to th ee ll d oe s n o t sh o w a n y e ffe ct o n its m e m b ra n ep o te n tia l
ort ca nputs to t e
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ort ca nputs to t eposterior medial (POm
HO) nucleusEPSPs showing the modulator signature :paired-pulsefacilitation, graded response, mGluR component; the driversignature : paired-pulse depression, all-or none response,no mGluR component
stimulation of layer :A e x a m p le o f e v o ke d E P S P s
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stimulation of layer6 of barrel cortex ina cell of theposterior medialnucleus
The EPSPsevoked by LFS (13 Hzfor 600 ms; for alltraces, stimulationintensity was 150 A) areblocked with application
of MK-801 andDNQX (top). With theseantagonists present,HFS (125 Hz for 600 ms)evoked a sustainedEPSP (2nd trace) that is
not blocked by MPEP,an mGluR5 antagonist(30 M, 3rd trace) butis blocked by LY367385,an mGluR1 antagonist(50 M, bottom).
:A e x a m p le o f e v o ke d E P S P s: -B p a ire d p u lse fa cilita tio n a n d g ra d e d
resp on se of E PS Ps:C e v id e n ce o f a n m G lu R 1 co m p o n e n t
stimulation of layer
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s u a o o aye5 of barrel cortex ina cell of theposterior medialnucleus
AfterblockingEPSPs with
DNQXand MK-801,neither LFS(50 Hz for
855 ms, top)nor HFS(125 Hz for855 ms,
bottom)
: e x a m p le o f e v o k e d E P S P s: -p a ire d p u ls e d e p re s sio n: - -a ll o r n o n e re sp o n s e o f E P S P s is a p p a re n t
ro m re s p o n s e s to in c re a s in g s tim u la tio nin te n s itie s: la c k o f m G lu R c o m p o n e n t
or-none EPSPs
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or-none EPSPsfrom cells of theposterior medialnucleus
The 3examples ofall-or-none
responses (and ) reflectstimulationfrom layer 5,
whereas the 5examples ofgradedresponses
(- - - and )
EPSPs evoked from
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separate stimulation oflayers 5 and 6 of barrelcortex in the same cellof the posterior medialnucleus
A, i and ii: paired-pulse effects, showingdepression for layer 5stimulation (Ai) and
facilitation for layer 6stimulation (Aii).B, i and ii:recruitment
properties, showing all-or-none response forlayer 5 stimulation (Bi)and graded responses
for layer 6 stimulation
EPSPs evoked fromi l i f
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separate stimulation oflayers 5 and 6 of barrelcortex in the samecellof the posteriormedial nucleus
C, i and ii:contribution ofmGluRs. Application ofDNQX and MK-801blocks EPSPs to LFS (9Hz for 755 ms) bothfrom layer 5 (Ci, top)andfrom layer 6 (Cii, top).
HFS (125 Hz for 755 ms)evokes nothing furtherfrom layer 5 (Ci, bottom)but evokes aprolonged EPSP from
layer 6 (Cii, middle), and
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discussionEPSPs showing the modulator signature :paired-pulsefacilitation, graded response, mGluR component; the driversignature : paired-pulse depression, all-or none response,no mGluR component
cortical
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corticalcommunicationinvolvinghigher-orderthalamic relays.
This hypothesis suggeststhat information arrivesinitially at the corticallevel after transmissionthrough a 1rst-order (FO)thalamic relay such as thelateral geniculate nucleus,ventral division of themedial geniculate nucleus(MGNv), or medial orlateral VP. Furthercorticocorticalcommunication in additionto or perhaps instead ofdirect pathways
involves transmission viahigher-order (HO)thalamic relays, such asthe pulvinar (Pul),magnocellular division ofthe medial geniculatenucleus or the POm. Aremaining issue is the
identity of directcorticocortical pathways
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Discussion
h is h yp o th esis su g g ests th at in fo rm atio nrrive s in itia lly a t th e co rtica l le ve l a fte r- ( )ra n sm issio n th ro u g h a 1 rst o rd e r F Oh alam ic relay su ch as th e lateral g en icu late,u cle u s v e n tra l d iv isio n o f th e m e d ia l( ) ,e n icu la te n u cle u s M G N v o r m e d ia l o r.ate ral V Pu rth e r co rtico co rtica l o m m u n ica tio n ind d itio n to o r p e rh a p s in ste a d o f d ire ct
-ath w ays in volves tran sm ission via h ig h er( ) ,rd er H O th a la m ic re lays su ch a s th e( ) ,u lv in a r P u l m a g n o ce llu la r d iv isio n o f th e.e d ia l g e n icu la te n u cle u s o r th e P O mrem ain in g issu e is th e id en tity o f d irectco rtico co rtica l a th w ays a s d rive r o r
ne mage
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ne magevaut millemots
ReviewThalamic Relay Functionsand Their Role inCorticocorticalCommunication:Generalizations from theVisual SystemR.W. Guillery1 andS.Murray Sherman2, ,1Department of Anatomy,University of WisconsinSchool of Medicine, 1300University Avenue,Madison, WI 53706 USA
2Department ofNeurobiology, StateUniversity of New York,Stony Brook, NY 11794USAAvailable online 22January 2002.
Questions
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Questions??
SomatosensoryCorticothalamic
Projections:Distinguishing
Drivers fromModulators
par
Iva Reichova et
S. MurrayShermanJournal of
Neurophysiology, 2004