Probabilistic atlas of human thalamic architecture based on
diffusion MRI
H
1
Johansen-Berg ,
1
Behrens ,
1
Sillery ,
2
Ciccarelli ,
2
Thompson ,
1
Smith ,
TEJ
E
O
A
SM
1Oxford Centre for FMRI of the Brain, University of Oxford, UK
2Institute of Neurology, Queen’s square, London, UK
PM
1
Matthews
Introduction
Methods.
•Thalamic activation seen during sensory, motor and cognitive tasks.
•Thalamic lesions affect sensory, executive and memory functions .
•Thalamo-cortical circuitry disrupted in neurological/psychiatric disorders.
Diffusion-weighted data were acquired in 11 subjects2. From each thalamic
voxel, we generated connectivity distributions3, and recorded probability of
connection to each of 7 cortical masks. We classified seed voxels according to
the cortical regions with which they showed the highest connection probability,
resulting in exclusive connectivity-defined regions (CDRs). Individual subject
CDRs (in standard space) were thresholded (>25% probability of connection),
binarised and overlaid to create a probabilistic atlas.
•However, borders between thalamic nuclei can only been reliably defined
post mortem so structure-function correlations are limited.
•We previously used diffusion tractography to parcellate the human thalamus
in vivo based on its cortical connectivity1.
A
C
B
EC
D
F
A. Thalamus. B. Connectivity distribution from a
seed voxel in MD nucleus terminates in the
prefrontal cortex. C. Axial slice from histological
atlas. D. Predicted classification of thalamic nuclei
according to cortical parcellation shown in E. F.
Classification of thalamic voxels according to the
cortical region with which they have maximum
probability of connection..
Web-based interface
Here, we present a probabilistic atlas of connectivity-based thalamic
architecture. The atlas can be used to assign likely functionalanatomical labels to thalamic activations or lesion sites.
http://www.fmrib.ox.ac.uk/connect
Inter-individual variability and probability maps
Functional-anatomical correspondence
Top. Thalamic segmentation for 11 individual subjects
Middle: Population probability maps showing extent of overlap
across subjects. Maps were created by thresholding (at >25% of
cortical pathways reaching that area) and binarising clusters for
each cortical area and each subject. These binarised clusters
were then overlaid so that the intensity in the group maps reflects
the number of subjects showing connectivity from that voxel.
Meta-analysis of motor and executive fMRI/PET activations showed close
correspondence between functionally and connectivity-defined regions
A
B
C
Bottom: Axial slices through the whole thalamus showing edges
of thresholded (at >4/11 subjects) group probability maps for
connection to each cortical region.
S1
M1
PMC
PFC
PPC
TEMP
OCC
100%
83%
66%
Functional correspondence: Pale grey surface represents thalamus A. Thalamic activation sites during motor
(blue) or executive (red) tasks. B. Co-localisation between motor activations and thalamic volumes with high
probability of connection to motor (blue), premotor (red) or somatosensory (green) cortices. C. Co-localisation
between executive activations and thalamic volumes with high probability of connection to prefrontal cortex.
50%
Connectivity profiles for activation centres.
Each row represents one activation centre, each column
represents connection to one cortical target. The
brightness of each cell represents the probability of
connection to that cortical target. Movement-related
activations tend to have high probabilities of connection
to sensorimotor, premotor and parietal cortices.
Executive and memory tasks tend to have very specific
high probability of connection to prefrontal cortex.
M1
PMC
S1
PPC
PFC
0
OCC
TEMP
1
Discussion
The atlas presented here could be particularly useful for assigning
probabilistic anatomical labels to thalamic activations when circuitry is
unknown. For example, although thalamic activation is observed during pain,
the nature of the thalamic involvement remains unclear and would be
illuminated by clarification of which functional subunits are activated.
The demonstration that connectivity-based parcellation is reproducible
across healthy subjects demonstrates the feasibility of this approach for
clinical studies. For example, the size/location of the thalamic sub-region
connected to prefrontal cortex could be directly compared between
schizophrenics and controls. Additionally, lesions of different thalamic sites
cause specific cognitive impairments4. Localising lesions on our connectivitybased atlas would determine the thalamo-cortical pathways affected and
enable more precise clinico-anatomical correlations to be made.
Acknowledgements. UK MRC (PMM, SMS, ES), UK EPSRC (TEJB, SMS), Wellcome Trust (HJB),
References 1. Behrens et al, 2003, Nature Neurosci 6, 750-7. 2. Wheeler-Kingshott et al, 2002, ISMRM 1118. 3.
Behrens et al, 2003, MRM 50, 1077-88. 4. Van der Werf, 2003, Neuropsychologia, 41, 1330-1344.