Assessing the effects of age on long white matter tracts using diffusion tensor tractography

NeuroImage

Volumn 46, Issue 2, 2009, Pages 530-541

  Davis, Simon W ^a   Dennis, Nancy A ^a,b   Buchler, Norbou G ^a,c   White, Leonard E ^b,c   Madden, David J ^b,c   Cabeza, Roberto ^a,b,c  

^a DUKE UNIVERSITY   (United States)

^b DUKE UNIVERSITY SCHOOL OF MEDICINE   (United States)

^c DUKE UNIVERSITY MEDICAL CENTER   (United States)

Author keywords

Aging; Demyelination; DTI; Radial diffusivity; Tractography

Indexed keywords

AGE DISTRIBUTION; AGED; AGING; ARTICLE; BRAIN DEGENERATION; CLINICAL ARTICLE; COGNITION; CONTROLLED STUDY; DIFFUSION TENSOR IMAGING; DIFFUSION TENSOR TRACTOGRAPHY; FEMALE; HUMAN; LIFESPAN; MALE; MENTAL PERFORMANCE; PRIORITY JOURNAL; TEMPORAL CORTEX; VISUAL MEMORY; WHITE MATTER;

ADULT; AGED; AGING; BRAIN; DIFFUSION MAGNETIC RESONANCE IMAGING; FEMALE; HUMANS; MALE; MIDDLE AGED; NERVE FIBERS, MYELINATED;

EID: 64449086421     PISSN: 10538119     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.neuroimage.2009.01.068     Document Type: Article

References (102)

1. Ashburner J., and Friston K.J. Voxel-based morphometry-the methods. Neuroimage 11 (2000) 805-821
2. Bartzokis G. Age-related myelin breakdown: a developmental model of cognitive decline and Alzheimer's disease. Neurobiol. Aging 25 (2004) 5-18 author reply 49-62
3. Bartzokis G., Sultzer D., Lu P.H., Nuechterlein K.H., Mintz J., and Cummings J.L. Heterogeneous age-related breakdown of white matter structural integrity: implications for cortical "disconnection" in aging and Alzheimer's disease. Neurobiol. Aging 25 (2004) 843-851
4. Basser P.J., Pajevic S., Pierpaoli C., Duda J., and Aldroubi A. In vivo fiber tractography using DT-MRI data. Magn. Reson. Med. 44 (2000) 625-632
5. Bassett D.L. A Stereoscopic Atlas of Human Anatomy (1952), Sawyer's Inc, Portland
6. Beaulieu C., and Allen P.S. Determinants of anisotropic water diffusion in nerves. Magn. Reson. Med. 31 (1994) 394-400
7. Bhagat Y.A., and Beaulieu C. Diffusion anisotropy in subcortical white matter and cortical gray matter: changes with aging and the role of CSF-suppression. J. Magn. Reson. Imaging 20 (2004) 216-227
8. Bucur B., Madden D.J., Spaniol J., Provenzale J.M., Cabeza R., White L.E., and Huettel S.A. Age-related slowing of memory retrieval: contributions of perceptual speed and cerebral white matter integrity. Neurobiol. Aging 29 (2007) 1070-1079
9. Burgel U., Amunts K., Hoemke L., Mohlberg H., Gilsbach J.M., and Zilles K. White matter fiber tracts of the human brain: three-dimensional mapping at microscopic resolution, topography and intersubject variability. Neuroimage 29 (2006) 1092-1105
10. Cabeza R. Hemispheric asymmetry reduction in older adults: the HAROLD model. Psychol. Aging 17 (2002) 85-100
11. Catani M., Howard R.J., Pajevic S., and Jones D.K. Virtual in vivo interactive dissection of white matter fasciculi in the human brain. Neuroimage 17 (2002) 77-94
12. Concha L., Gross D.W., Wheatley B.M., and Beaulieu C. Diffusion tensor imaging of time-dependent axonal and myelin degradation after corpus callosotomy in epilepsy patients. Neuroimage 32 (2006) 1090-1099
13. Corouge I., Fletcher P.T., Joshi S., Gouttard S., and Gerig G. Fiber tract-oriented statistics for quantitative diffusion tensor MRI analysis. Med. Image Anal. 10 (2006) 786-798
14. Curran E.J. A new association fiber tract in the cerebrum. With remarks on the fiber tract dissection of studying the brain. J. Comp. Neurol. 19 (1909) 645-656
15. Daselaar S.M., Browndyke J., and Cabeza R. Functional neuroimaging of cognitive aging. In: Cabeza R., and Kingstone A. (Eds). Handbook of Functional Neuroimaging of Cognition. 2nd ed (2006), MIT Press
16. Daselaar S.M., and Cabeza R. Age-related changes in hemispheric organization. In: Cabeza R., Nyberg L., and Park D.C. (Eds). Cognitive Neuroscience of Aging (2005), Oxford University Press, Oxford
17. Dubois J., Dehaene-Lambertz G., Perrin M., Mangin J.F., Cointepas Y., Duchesnay E., Le Bihan D., and Hertz-Pannier L. Asynchrony of the early maturation of white matter bundles in healthy infants: quantitative landmarks revealed noninvasively by diffusion tensor imaging. Hum. Brain. Mapp. 29 (2008) 14-27
18. Duvernoy H. The Human Brain, Surface, Blood Supply, and Three-Dimensional Sectional Anatomy (1999), Springer-Verlag, Vienna
19. Ebeling U., and von Cramon D. Topography of the uncinate fascicle and adjacent temporal fiber tracts. Acta. Neurochir. 115 (1992) 143-148
20. Eluvathingal T.J., Hasan K.M., Kramer L., Fletcher J.M., and Ewing-Cobbs L. Quantitative diffusion tensor tractography of association and projection fibers in normally developing children and adolescents. Cereb. Cortex 17 (2007) 2760-2768
21. Feldman M.L., and Peters A. Ballooning of myelin sheaths in normally aged macaques. J. Neurocytol. 27 (1998) 605-614
22. Flechsig P. Developmental (myelogenetic) localisation of the cerebral cortex in the human subject. Lancet 2 (1901) 1027-1029
23. Gao W., Lin W., Chen Y., Gerig G., Smith J.K., Jewells V., and Gilmore J.H. Temporal and spatial development of axonal maturation and myelination of white matter in the developing brain. AJNR. Am. J. Neuroradiol. 1 (2008) 1
24. Geula C., Wu C.K., Saroff D., Lorenzo A., Yuan M., and Yankner B.A. Aging renders the brain vulnerable to amyloid beta-protein neurotoxicity. Nat. Med. 4 (1998) 827-831
25. Giedd J.N., Blumenthal J., Jeffries N.O., Castellanos F.X., Liu H., Zijdenbos A., Paus T., Evans A.C., and Rapoport J.L. Brain development during childhood and adolescence: a longitudinal MRI study. Nat. Neurosci. 2 (1999) 861-863
26. Giorgio A., Watkins K.E., Douaud G., James A.C., James S., De Stefano N., Matthews P.M., Smith S.M., and Johansen-Berg H. Changes in white matter microstructure during adolescence. Neuroimage 39 (2008) 52-61
27. Glenn O.A., Henry R.G., Berman J.I., Chang P.C., Miller S.P., Vigneron D.B., and Barkovich A.J. DTI-based three-dimensional tractography detects differences in the pyramidal tracts of infants and children with congenital hemiparesis. J. Magn. Reson. Imaging 18 (2003) 641-648
28. Glisky E.L., Polster M.R., and Routhieaux B.C. Double dissociation between item and source memory. Neuropsychology 9 (1995) 229-235
29. Glisky E.L., Rubin S.R., and Davidson P.S. Source memory in older adults: an encoding or retrieval problem?. J. Exp. Psychol. Learn Mem. Cogn. 27 (2001) 1131-1146
30. Goodlett C.B., Fletcher P.T., Gilmore J.H., and Gerig G. Group analysis of DTI fiber tract statistics with application to neurodevelopment. Neuroimage 45 (2008) S133-S142
31. Gould R.L., Brown R.G., Owen A.M., ffytche D.H., and Howard R.J. fMRI BOLD response to increasing task difficulty during successful paired associates learning. Neuroimage 20 (2003) 1006-1019
32. Grady C.L., McIntosh A.R., Horwitz B., Maisog J.M., Ungerleider L.G., Mentis M.J., Pietrini P., Schapiro M.B., and Haxby J.V. Age-related reductions in human recognition memory due to impaired encoding. Science 269 (1995) 218-221
33. Greenwood P.M. The frontal aging hypothesis evaluated. J. Int. Neuropsychol. Soc. 6 (2000) 705-726
34. Grieve S.M., Williams L.M., Paul R.H., Clark C.R., and Gordon E. Cognitive aging, executive function, and fractional anisotropy: a diffusion tensor MR imaging study. AJNR. Am. J. Neuroradiol. 28 (2007) 226-235
35. Gutchess A.H., Welsh R.C., Hedden T., Bangert A., Minear M., Liu L.L., and Park D.C. Aging and the neural correlates of successful picture encoding: frontal activations compensate for decreased medial-temporal activity. J. Cogn. Neurosci. 17 (2005) 84-96
36. Hayakawa K., Konishi Y., Kuriyama M., Konishi K., and Matsuda T. Normal brain maturation in MRI. Eur. J. Radiol. 12 (1991) 208-215
37. Head D., Buckner R.L., Shimony J.S., Williams L.E., Akbudak E., Conturo T.E., McAvoy M., Morris J.C., and Snyder A.Z. Differential vulnerability of anterior white matter in nondemented aging with minimal acceleration in dementia of the Alzheimer type: evidence from diffusion tensor imaging. Cereb. Cortex 14 (2004) 410-423
38. Husain J., and Juurlink B.H. Oligodendroglial precursor cell susceptibility to hypoxia is related to poor ability to cope with reactive oxygen species. Brain Res. 698 (1995) 86-94
39. Jensen J.H., Helpern J.A., Ramani A., Lu H., and Kaczynski K. Diffusional kurtosis imaging: the quantification of non-Gaussian water diffusion by means of magnetic resonance imaging. Magn. Reson. Med. 53 (2005) 1432-1440
40. Kennedy K.M., Erickson K.I., Rodrigue K.M., Voss M.W., Colcombe S.J., Kramer A.F., Acker J.D., and Raz N. Age-related differences in regional brain volumes: a comparison of optimized voxel-based morphometry to manual volumetry. Neurobiol. Aging. (2008) doi:10.1016/j.neurobiolaging.2007.12.020
41. Kier E.L., Staib L.H., Davis L.M., and Bronen R.A. MR imaging of the temporal stem: anatomic dissection tractography of the uncinate fasciculus, inferior occipitofrontal fasciculus, and Meyer's loop of the optic radiation. AJNR. Am. J. Neuroradiol. 25 (2004) 677-691
42. Kinney H.C., Brody B.A., Kloman A.S., and Gilles F.H. Sequence of central nervous system myelination in human infancy. II. Patterns of myelination in autopsied infants. J. Neuropathol. Exp. Neurol. 47 (1988) 217-234
43. Lamantia A.S., and Rakic P. Cytological and quantitative characteristics of four cerebral commissures in the rhesus monkey. J. Comp. Neurol. 291 (1990) 520-537
44. Landis J.R., and Koch G.G. The measurement of observer agreement for categorical data. Biometrics 33 (1977) 159-174
45. Lebel C., Walker L., Leemans A., Phillips L., and Beaulieu C. Microstructural maturation of the human brain from childhood to adulthood. Neuroimage 40 (2008) 1044-1055
46. Madden D.J., Spaniol J., Costello M.C., Bucur B., White L.E., Cabeza R., Davis S.W., Dennis N.A., Provenzale J.M., and Huettel S.A. Cerebral white matter integrity mediates adult age differences in cognitive performance. J. Cogn. Neurosci. 21 (2009) 289-302
47. Madden D.J., Turkington T.G., Provenzale J.M., Denny L.L., Langley L.K., Hawk T.C., and Coleman R.E. Aging and attentional guidance during visual search: functional neuroanatomy by positron emission tomography. Psychol. Aging 17 (2002) 24-43
48. Madden D.J., Whiting W.L., Huettel S.A., White L.E., MacFall J.R., and Provenzale J.M. Diffusion tensor imaging of adult age differences in cerebral white matter: relation to response time. Neuroimage 21 (2004) 1174-1181
49. Madden D.J., Spaniol J., Whiting W.L., Bucur B., Provenzale J.M., Cabeza R., White L.E., and Huettel S.A. Adult age differences in the functional neuroanatomy of visual attention: a combined fMRI and DTI study. Neurobiol. Aging 28 (2006) 459-476
50. Madden D.J., Spaniol J., Bucur B., and Whiting W.L. Age-related increase in top-down activation of visual features. Q. J. Exp. Psychol. (Colchester) 60 (2007) 644-651
51. Markowitsch H.J. Which brain regions are critically involved in the retrieval of old episodic memory?. Brain Res. Brain Res. Rev. 21 (1995) 117-127
52. Meier-Ruge W., Ulrich J., Bruhlmann M., and Meier E. Age-related white matter atrophy in the human brain. Ann. N. Y. Acad. Sci. 673 (1992) 260-269
53. Mori S., and van Zijl P.C. Fiber tracking: principles and strategies - a technical review. NMR Biomed. 15 (2002) 468-480
54. Moscovitch M., and Winocur G. The neuropsychology of memory and aging. In: Craik F.I.M., and Salthouse T.A. (Eds). The Handbook of Aging and Cognition (1992), Lawrence Erlbaum Associates, Hillsdale, NJ 315-372
55. O'Donnell L., and Westin C.F. High-dimensional white matter atlas generation and group analysis. Med. Image Comput. Comput. Assist. Interv. Int. Conf. Med. Image. Comput. Comput. Assist. Interv. 9 (2006) 243-251
56. O'Sullivan M., Jones D.K., Summers P.E., Morris R.G., Williams S.C., and Markus H.S. Evidence for cortical "disconnection" as a mechanism of age-related cognitive decline. Neurology 57 (2001) 632-638
57. Owen A.M., Morris R.G., Sahakian B.J., Polkey C.E., and Robbins T.W. Double dissociations of memory and executive functions in working memory tasks following frontal lobe excisions, temporal lobe excisions or amygdalo-hippocampectomy in man. Brain 119 Pt. 5 (1996) 1597-1615
58. Paus T., Zijdenbos A., Worsley K., Collins D.L., Blumenthal J., Giedd J.N., Rapoport J.L., and Evans A.C. Structural maturation of neural pathways in children and adolescents: in vivo study. Science 283 (1999) 1908-1911
59. Persson J., Nyberg L., Lind J., Larsson A., Nilsson L.G., Ingvar M., and Buckner R.L. Structure-function correlates of cognitive decline in aging. Cereb. Cortex 16 (2006) 907-915
60. Peters A., and Sethares C. Aging and the myelinated fibers in prefrontal cortex and corpus callosum of the monkey. J. Comp. Neurol. 442 (2002) 277-291
61. Peters A., Moss M.B., and Sethares C. Effects of aging on myelinated nerve fibers in monkey primary visual cortex. J. Comp. Neurol. 419 (2000) 364-376
62. Pfefferbaum A., Adalsteinsson e., and sullivan e.v. frontal circuitry degradation marks healthy adult aging: evidence from diffusion tensor imaging. Neuroimage 26 (2005) 891-899
63. Price G., Cercignani M., Parker G.J., Altmann D.R., Barnes T.R., Barker G.J., Joyce E.M., and Ron M.A. White matter tracts in first-episode psychosis: a DTI tractography study of the uncinate fasciculus. Neuroimage 39 (2008) 949-955
64. Rabbitt P., and Lowe C. Patterns of cognitive ageing. Psychol. Res. 63 (2000) 308-316
65. Raz N. Aging of the brain and its impact on cognitive performance: integration of structural and functional findings. In: Craik F.I.M., and Salthouse T.A. (Eds). The Handbook of Aging and Cognition (2000), Lawrence Erlbaum, London
66. Raz N. The aging brain observed in vivo: differential changes and their modifiers. In: Cabeza R., Nyberg L., and Park D.C. (Eds). Cognitive Neuroscience of Aging (2005), Oxford University Press 19-57
67. Raz N., Gunning F.M., Head D., Dupuis J.H., McQuain J., Briggs S.D., Loken W.J., Thornton A.E., and Acker J.D. Selective aging of the human cerebral cortex observed in vivo: differential vulnerability of the prefrontal gray matter. Cereb. Cortex 7 (1997) 268-282
68. Raz N., Lindenberger U., Rodrigue K.M., Kennedy K.M., Head D., Williamson A., Dahle C., Gerstorf D., and Acker J.D. Regional brain changes in aging healthy adults: general trends, individual differences and modifiers. Cereb. Cortex 15 (2005) 1676-1689
69. Resnick S.M., Pham D.L., Kraut M.A., Zonderman A.B., and Davatzikos C. Longitudinal magnetic resonance imaging studies of older adults: a shrinking brain. J. Neurosci. 23 (2003) 3295-3301
70. Robbins T.W., James M., Owen A.M., Sahakian B.J., Lawrence A.D., McInnes L., and Rabbitt P.M. A study of performance on tests from the CANTAB battery sensitive to frontal lobe dysfunction in a large sample of normal volunteers: implications for theories of executive functioning and cognitive aging. Cambridge Neuropsychological Test Automated Battery. J. Int. Neuropsychol. Soc. 4 (1998) 474-490
71. Ronen I., Ugurbil K., and Kim D. How does DWI correlate with white matter structures?. Magn. Reson. Med. 54 (2005) 317
72. Sakuma H., Nomura Y., Takeda K., Tagami T., Nakagawa T., Tamagawa Y., Ishii Y., and Tsukamoto T. Adult and neonatal human brain: diffusional anisotropy and myelination with diffusion-weighted MR imaging. Radiology 180 (1991) 229-233
73. Salat D.H., Kaye J.A., and Janowsky J.S. Prefrontal gray and white matter volumes in healthy aging and Alzheimer disease. Arch. Neurol. 56 (1999) 338-344
74. Salat D.H., Tuch D.S., Hevelone N.D., Fischl B., Corkin S., Rosas H.D., and Dale A.M. Age-related changes in prefrontal white matter measured by diffusion tensor imaging. Ann. N. Y. Acad. Sci. 1064 (2005) 37-49
75. Scahill R.I., Frost C., Jenkins R., Whitwell J.L., Rossor M.N., and Fox N.C. A longitudinal study of brain volume changes in normal aging using serial registered magnetic resonance imaging. Arch. Neurol. 60 (2003) 989-994
76. Schmierer K., Scaravilli F., Altmann D.R., Barker G.J., and Miller D.H. Magnetization transfer ratio and myelin in postmortem multiple sclerosis brain. Ann. Neurol. 56 (2004) 407-415
77. Smith S.M., Zhang Y., Jenkinson M., Chen J., Matthews P.M., Federico A., and De Stefano N. Accurate, robust, and automated longitudinal and cross-sectional brain change analysis. Neuroimage 17 (2002) 479-489
78. Smith S.M., Jenkinson M., Woolrich M.W., Beckmann C.F., Behrens T.E., Johansen-Berg H., Bannister P.R., De Luca M., Drobnjak I., Flitney D.E., Niazy R.K., Saunders J., Vickers J., Zhang Y., De Stefano N., Brady J.M., and Matthews P.M. Advances in functional and structural MR image analysis and implementation as FSL. Neuroimage 23 Suppl. 1 (2004) S208-S219
79. Smith S.M., Jenkinson M., Johansen-Berg H., Rueckert D., Nichols T.E., Mackay C.E., Watkins K.E., Ciccarelli O., Cader M.Z., Matthews P.M., and Behrens T.E. Tract-based spatial statistics: voxelwise analysis of multi-subject diffusion data. Neuroimage 31 (2006) 1487-1505
80. Snook L., Paulson L.A., Roy D., Phillips L., and Beaulieu C. Diffusion tensor imaging of neurodevelopment in children and young adults. Neuroimage 26 (2005) 1164-1173
81. Song S.K., Sun S.W., Ramsbottom M.J., Chang C., Russell J., and Cross A.H. Dysmyelination revealed through MRI as increased radial (but unchanged axial) diffusion of water. Neuroimage 17 (2002) 1429-1436
82. Song S.K., Sun S.W., Ju W.K., Lin S.J., Cross A.H., and Neufeld A.H. Diffusion tensor imaging detects and differentiates axon and myelin degeneration in mouse optic nerve after retinal ischemia. Neuroimage 20 (2003) 1714-1722
83. Song S.K., Yoshino J., Le T.Q., Lin S.J., Sun S.W., Cross A.H., and Armstrong R.C. Demyelination increases radial diffusivity in corpus callosum of mouse brain. Neuroimage 26 (2005) 132-140
84. Sowell E.R., Trauner D.A., Gamst A., and Jernigan T.L. Development of cortical and subcortical brain structures in childhood and adolescence: a structural MRI study. Dev. Med. Child Neurol. 44 (2002) 4-16
85. Sowell E.R., Thompson P.M., Leonard C.M., Welcome S.E., Kan E., and Toga A.W. Longitudinal mapping of cortical thickness and brain growth in normal children. J. Neurosci. 24 (2004) 8223-8231
86. Sullivan E.V., and Pfefferbaum A. Diffusion tensor imaging and aging. Neurosci. Biobehav. Rev. 30 (2006) 749-761
87. Sullivan E.V., Adalsteinsson E., Hedehus M., Ju C., Moseley M., Lim K.O., and Pfefferbaum A. Equivalent disruption of regional white matter microstructure in ageing healthy men and women. Neuroreport 12 (2001) 99-104
88. Sullivan E.V., Adalsteinsson E., and Pfefferbaum A. Selective age-related degradation of anterior callosal fiber bundles quantified in vivo with fiber tracking. Cereb. Cortex 16 (2006) 1030-1039
89. Sullivan E.V., Rohlfing T., and Pfefferbaum A. Quantitative fiber tracking of lateral and interhemispheric white matter systems in normal aging: relations to timed performance. Neurobiol. Aging 1 (2008) 1
90. Sun S.W., Liang H.F., Schmidt R.E., Cross A.H., and Song S.K. Selective vulnerability of cerebral white matter in a murine model of multiple sclerosis detected using diffusion tensor imaging. Neurobiol. Dis. 28 (2007) 30-38
91. Tang Y., and Nyengaard J.R. A stereological method for estimating the total length and size of myelin fibers in human brain white matter. J. Neurosci. Methods 73 (1997) 193-200
92. Thomalla G., Glauche V., Koch M.A., Beaulieu C., Weiller C., and Rother J. Diffusion tensor imaging detects early Wallerian degeneration of the pyramidal tract after ischemic stroke. Neuroimage 22 (2004) 1767-1774
93. Trip S.A., Wheeler-Kingshott C., Jones S.J., Li W.Y., Barker G.J., Thompson A.J., Plant G.T., and Miller D.H. Optic nerve diffusion tensor imaging in optic neuritis. Neuroimage 30 (2006) 498-505
94. Vernooij M.W., de Groot M., van der Lugt A., Ikram M.A., Krestin G.P., Hofman A., Niessen W.J., and Breteler M.M. White matter atrophy and lesion formation explain the loss of structural integrity of white matter in aging. Neuroimage 43 (2008) 470-477
95. Vogt B.A., Finch D.M., and Olson C.R. Functional heterogeneity in cingulate cortex: the anterior executive and posterior evaluative regions. Cereb. Cortex 2 (1992) 435-443
96. Wakana S., Jiang H., Nagae-Poetscher L.M., van Zijl P.C., and Mori S. Fiber tract-based atlas of human white matter anatomy. Radiology 230 (2004) 77-87
97. Wakana S., Caprihan A., Panzenboeck M.M., Fallon J.H., Perry M., Gollub R.L., Hua K., Zhang J., Jiang H., Dubey P., Blitz A., van Zijl P., and Mori S. Reproducibility of quantitative tractography methods applied to cerebral white matter. Neuroimage 36 (2007) 630-644
98. West R.L. An application of prefrontal cortex function theory to cognitive aging. Psychol. Bull. 120 (1996) 272-292
99. Wozniak J.R., and Lim K.O. Advances in white matter imaging: a review of in vivo magnetic resonance methodologies and their applicability to the study of development and aging. Neurosci. Biobehav. Rev. 30 (2006) 762-774
100. Xu D., Mori S., Solaiyappan M., van Zijl P.C., and Davatzikos C. A framework for callosal fiber distribution analysis. Neuroimage 17 (2002) 1131-1143
101. Yakovlev P.I., and Lecours A.R. In: Minkowski A. (Ed). Regional Development of the Brain in Early Life (1967), Blackwell Scientific, Boston
102. Yasmin H., Nakata Y., Aoki S., Abe O., Sato N., Nemoto K., Arima K., Furuta N., Uno M., Hirai S., Masutani Y., and Ohtomo K. Diffusion abnormalities of the uncinate fasciculus in Alzheimer's disease: diffusion tensor tract-specific analysis using a new method to measure the core of the tract. Neuroradiology 50 (2008) 293-299