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White matter tracts in first-episode psychosis: a DTI tractography study of the uncinate fasciculus.

Price G, Cercignani M, Parker GJ, Altmann DR, Barnes TR, Barker GJ, Joyce EM, Ron MA - Neuroimage (2007)

Bottom Line: Fractional anisotropy (FA) and probability of connection were obtained for every voxel in the tract, and the group means and distributions of these variables were compared.The spread of the FA distribution in the upper tail, as measured by the squared coefficient of variance (SCV), was reduced in the left UF in the patient group, indicating that the number of voxels with high FA values was reduced in the core of the tract and suggesting the presence of changes in fibre alignment and tract coherence in the patient group.The SCV of FA was lower in females across both groups and there was no correlation between the SCV of FA and clinical ratings.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neurology, University College London, Queen Square, London, UK. g.price@ion.ucl.ac.uk

ABSTRACT
A model of disconnectivity involving abnormalities in the cortex and connecting white matter pathways may explain the symptoms and cognitive abnormalities of schizophrenia. Recently, diffusion imaging tractography has made it possible to study white matter pathways in detail, and we present here a study of patients with first-episode psychosis using this technique. We studied the uncinate fasciculus (UF), the largest white matter tract that connects the frontal and temporal lobes, two brain regions significantly implicated in schizophrenia. Nineteen patients with first-episode schizophrenia and 23 controls were studied using a probabilistic tractography algorithm (PICo). Fractional anisotropy (FA) and probability of connection were obtained for every voxel in the tract, and the group means and distributions of these variables were compared. The spread of the FA distribution in the upper tail, as measured by the squared coefficient of variance (SCV), was reduced in the left UF in the patient group, indicating that the number of voxels with high FA values was reduced in the core of the tract and suggesting the presence of changes in fibre alignment and tract coherence in the patient group. The SCV of FA was lower in females across both groups and there was no correlation between the SCV of FA and clinical ratings.

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Related in: MedlinePlus

Average reconstruction of the uncinate fasciculus in controls. The map was obtained by averaging a binary mask of the tract for every subject after normalisation. The colour scale indicates the degree of overlap between subjects. ‘0’ represents minimal overlap, ‘1’ represents maximal overlap.
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fig2: Average reconstruction of the uncinate fasciculus in controls. The map was obtained by averaging a binary mask of the tract for every subject after normalisation. The colour scale indicates the degree of overlap between subjects. ‘0’ represents minimal overlap, ‘1’ represents maximal overlap.

Mentions: PICo was run from every voxel in the seed region, and only trajectories traversing the through region were retained. The final output was obtained by taking, at each voxel in the brain, the maximum probability value across the probabilistic maps obtained from each seed point. The resultant connectivity maps were thresholded to include only voxels with a probabilistic connection of > 5%. This particular threshold has been used in previous studies (Ciccarelli et al., 2006; Powell et al., 2004) in order to eliminate the voxels most likely to be affected by image noise. The thresholded connectivity map was binarized to obtain an image of the segmented uncinate fasciculus as in our previous study of the corpus callosum (Price et al., 2007). Images were normalized using the same algorithm as above (Jenkinson and Smith, 2001) to a stereotactic space (Montréal Neurological Institute, MNI) using the standard echo planar image template in SPM2 (Wellcome Department of Cognitive Neurology, Institute of Neurology, London, UK) running in MATLAB (MathWorks, Natick, MA, USA) and averaged on a voxel-by-voxel basis to produce a map that displayed of the degree of tract overlap between subjects within each group. An example in the control group, similar in appearance to the patient group, is shown in Fig. 2.


White matter tracts in first-episode psychosis: a DTI tractography study of the uncinate fasciculus.

Price G, Cercignani M, Parker GJ, Altmann DR, Barnes TR, Barker GJ, Joyce EM, Ron MA - Neuroimage (2007)

Average reconstruction of the uncinate fasciculus in controls. The map was obtained by averaging a binary mask of the tract for every subject after normalisation. The colour scale indicates the degree of overlap between subjects. ‘0’ represents minimal overlap, ‘1’ represents maximal overlap.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2387199&req=5

fig2: Average reconstruction of the uncinate fasciculus in controls. The map was obtained by averaging a binary mask of the tract for every subject after normalisation. The colour scale indicates the degree of overlap between subjects. ‘0’ represents minimal overlap, ‘1’ represents maximal overlap.
Mentions: PICo was run from every voxel in the seed region, and only trajectories traversing the through region were retained. The final output was obtained by taking, at each voxel in the brain, the maximum probability value across the probabilistic maps obtained from each seed point. The resultant connectivity maps were thresholded to include only voxels with a probabilistic connection of > 5%. This particular threshold has been used in previous studies (Ciccarelli et al., 2006; Powell et al., 2004) in order to eliminate the voxels most likely to be affected by image noise. The thresholded connectivity map was binarized to obtain an image of the segmented uncinate fasciculus as in our previous study of the corpus callosum (Price et al., 2007). Images were normalized using the same algorithm as above (Jenkinson and Smith, 2001) to a stereotactic space (Montréal Neurological Institute, MNI) using the standard echo planar image template in SPM2 (Wellcome Department of Cognitive Neurology, Institute of Neurology, London, UK) running in MATLAB (MathWorks, Natick, MA, USA) and averaged on a voxel-by-voxel basis to produce a map that displayed of the degree of tract overlap between subjects within each group. An example in the control group, similar in appearance to the patient group, is shown in Fig. 2.

Bottom Line: Fractional anisotropy (FA) and probability of connection were obtained for every voxel in the tract, and the group means and distributions of these variables were compared.The spread of the FA distribution in the upper tail, as measured by the squared coefficient of variance (SCV), was reduced in the left UF in the patient group, indicating that the number of voxels with high FA values was reduced in the core of the tract and suggesting the presence of changes in fibre alignment and tract coherence in the patient group.The SCV of FA was lower in females across both groups and there was no correlation between the SCV of FA and clinical ratings.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neurology, University College London, Queen Square, London, UK. g.price@ion.ucl.ac.uk

ABSTRACT
A model of disconnectivity involving abnormalities in the cortex and connecting white matter pathways may explain the symptoms and cognitive abnormalities of schizophrenia. Recently, diffusion imaging tractography has made it possible to study white matter pathways in detail, and we present here a study of patients with first-episode psychosis using this technique. We studied the uncinate fasciculus (UF), the largest white matter tract that connects the frontal and temporal lobes, two brain regions significantly implicated in schizophrenia. Nineteen patients with first-episode schizophrenia and 23 controls were studied using a probabilistic tractography algorithm (PICo). Fractional anisotropy (FA) and probability of connection were obtained for every voxel in the tract, and the group means and distributions of these variables were compared. The spread of the FA distribution in the upper tail, as measured by the squared coefficient of variance (SCV), was reduced in the left UF in the patient group, indicating that the number of voxels with high FA values was reduced in the core of the tract and suggesting the presence of changes in fibre alignment and tract coherence in the patient group. The SCV of FA was lower in females across both groups and there was no correlation between the SCV of FA and clinical ratings.

Show MeSH
Related in: MedlinePlus