van wedeen [email protected] - brainmapping.org€¦ · water diffusion traces tissue fiber...
TRANSCRIPT
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Dejerine 1895 Brodmann 1909 Cajal 1911
While gray matter has been mapped successfullyfor 100 years, white matter and connectivity remainproblematic
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Felleman & Van Essen, 1989rhesus visual system
“It is intolerable that we donot have a knowledge of theconnectivity of the humanbrain” - Crick & Jones, 1993
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tissue
Diffusion MRI - tissue structure is traced by 3D patterns of water diffusion 1994: diffusion tensors show average fiber directions
diffusion tensor
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DTI tractography - invention and critiqueWedeen et al ISMRM 1995
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Myocardial fiber geometry for optimum efficiency
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The main reason neuro anatomy is moredifficult to figure out than other kinds of anatomy -
"fiber crossing" or overlap of structures in 3D
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Neuroanatomy is hard because neural structuresfreely overlap in 3D
macaque tracers - Pandya & Schmahmann
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Pathway overlap is a defining characteristic of the brain
not brainy brainy
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x-ray, overlap CT, overlap resolved
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To un-cross a curve, map it into a position-orientationspace with a “blow-up” transform
{x, y} -> {x, y, dy/dx} = {x, y, θ}
x
yθ
blow-up
x
y
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1. DSI - imaging the 6-dimensional brain
2. The connectome
3. Limbic system and hippocampus
4. Prospects
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DTI: 7 q-samples, recon with tensor fitDSI: 500 q-samles, recon with 3DFT
q-space
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brain tissue
Water diffusion traces tissue fiber structure2000: breakthrough diffusion spectrum MRI (DSI) resolvesoverlapping fiber pathways
diffusion spectrum
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Diffusion-limited diffusion MRI. Resolution of diffusion MRI fortissue microstructure Reff is limited by two factors:
• diffusion "camera resolution" q = GT
• "motion blur" √2DT due to diffusion itself
hence Reff = (q-2 + 2DT)1/2
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Consequences:
For any gradient G, there is a best-possible micro-resolution
Reff ≈ (D/Gmax)1/3
For any diffusion D, there is a universal optimum b-value
bopt ≈ π2/6D
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80 mT/m
320 mT/m
36 mT/m
Δ ms
Reff3 (µ3)
bopt(G,∆) = π2/6D
D = 0.2 Dwaterdif
fusion
-limite
d
gradient-limited
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Heresy:
Angular resolution is a useless idea, because it's model-dependent
In other words, it means whatever somebody wants it to mean.
That's why it's so useful.
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DSI directions of maximum diffusion 3T human in vivo
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Diffusion spectrum MRI and computed fiber paths (human pons)
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Macaque3D MRI - paths superimpose 6D DSI - paths resolved
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Rat DSI paths of a saggital slice
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Cat andmouse
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Owl monkey DSI - 3D paths of 1 slice
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DSI pathways of macaque cerebral hemisphere
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DSI human in vivo 3T
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DSI cortical connectivity in macaqueDSI Petrides & Pandya
area 10
BA10 important in schizophrenia, language
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Optic chiasm
DSI DTI
descusationWedeen et al Neruoimage 2008 in press
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DSI vs DTI - centrum semiovale of macaque
DSI DTI
cc
SLF2
cst
cc broken
missing
fictional
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CerebellumDTI DSI
transverse system
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Tractography in caudate nucleus -Amygdalo-striate bundle of Muratoff
DTI DSI
Wedeen et al Neruoimage 2008 in press
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Tracer and DSI - SLFIII
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CC
MB
FOF
CRCB
SLF II
Macaque DSI and isotope gold standardMuratoff bundle in context
Pandya & Schmahmann
Schmahmann et al Brain 2007
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Wedeen VJ, Schmahmann JD, Wang R, Dai G, D’Arceuil HE, de Crespigny AJ
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1. DSI - imaging the 6-dimensional brain
2. The connectome
3. Limbic system and hippocampus
4. Prospects
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Principles of organization common to all cortical areas
Association fibersLocalNeighborhoodLong
CordCommissural fibersSubcortical bundle
Striatal fibersMuratoff bundleExternal capsule
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SLF3
corticospinal tract
cortex
horizontal intracorticalfibers
Rhesus motor cortex connections of DTI vs DSI
DTI DSI
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DSI connectivity of macaque superior frontal gyrus
Schmahmann JD, Pandya DN, Wang R, Dai G, D’Arceuil HE, de Crespigny AJ, Wedeen VJ
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DSI
M1-FEF
parcellation
Macaque connectomes
DSI cocomac
Hagmann PLoS Biol 2008
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DSI in vivo human human connectome
Hagmann et al PLoS Biol 2008
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Human connectome hubs and core
Hagmann et al PLoS Biol 2008
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1. DSI - imaging the 6-dimensional brain
2. The connectome
3. Limbic system and hippocampus
4. Prospects
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Macaque circuit of Papez ex vivo
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Macaque cingulum bundlemorphology explained by development
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Human limbic circuit elements - CIND UCSF VA
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Cingulum bundle human DSI in vivo 3T
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Human temporal lobe / hippocampus ex vivo
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Human hippocampus ex vivo DSIdigital dissection
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Homologous woven motif of hippocampal pathways in mouse,owl monkey, and human
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Macaque calcarine connections
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1. DSI - imaging the 6-dimensional brain
2. The connectome
3. Limbic system and hippocampus
4. Prospectsdevelopmentcortex
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birth
Cat DSI day 100
Takahasi et al ISRMR 2008
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Day 100Day 0 Day 35
Development of cortico-thalamic tracts in cat
Takahasi et al ISRMR 2008
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Human cortex specimens normal control vs. polymicrogyria
Ellen Grant, RP Wang, A deCrespigny, VJ Wedeen - MGH Radiology
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Human cortex 300u
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Intracortical connectivity
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Rat cortex DSI
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1 2 3 4 5 6
cingulateA plane ofmaximum diffusion
1 2 3 4 5 6
Mouse DSI - planar diffusion reveals cortical structure
c. callosum
nigrostriatum
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DSI tractography rabbit - conventional (L) and cortex(R)
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Rhesus monkey cortical paths -a noninvasive Brodmann map?
DSI diffusion planestraced tangent to cortex
TG
V2
V1
10
41-2
TEmTs
L
46
96D
3
6Va
6Vb 14VA
13
PrCO
12
TEc,r
Tpt
Preuss
DSI diffusion planes tracedtangent to cortex
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Mouse brain automated multivariate spectral segmentationof DSI planar structure
Paxinos atlas DSI planar structure
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