CONTRIBUTIONS À LA RECHERCHE

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1 WORSLEY, Keith 1 CONTRIBUTIONS À LA RECHERCHE a. Articles publiés dans des revues avec comité de lecture (RAC) 1. Aston, J.A.D., Gunn, R.N., Worsley, K.J., Ma, Y., Evans, A.C. & Dagher, A. (2000). A statistical model for the analysis of positron emission tomography neuroreceptor ligand data. NeuroImage, 12: Andrade, A., Kherif, F., Mangin, J-F., Paradis, A-L., Worsley, K.J., Simon, O., Dehaene, S., Le Bihan, D. & Poline, J-B. (2001). Detection of fmri activation using cortical surface mapping. Human Brain Mapping, 12: Kiebel, S.J., Poline, J-B., Friston, K.J., Holmes, A.P. & Worsley, K.J. (1999). Robust smoothness estimation in statistical parametric maps using normalised residuals from the general linear model. NeuroImage, 10: Pike, G.B., De Stefano, N., Narayanan, S., Worsley, K.J., Pelletier, D., Francis, G.S., Antel, J.P. & Arnold, D.L. (1999). Imaging pre-lesional pathology in multiple sclerosis using magnetization transfer. Radiology, 215: Worsley, K.J., Andermann, M., Koulis, T., MacDonald, D. & Evans, A.C. (1999). Detecting changes in nonisotropic images. Human Brain Mapping, 8: Worsley, K.J. and Friston, K.J. (2000). A test for a conjunction. Statistics and Probability Letters, 47: Friston, K.J., Holmes, A.P. & Worsley, K.J. (1999). How many subjects constitute a study?. NeuroImage, 10: Paus, T., Zijdenbos, A., Worsley, K.J., Collins, D.L., Blumenthal, J., Giedd, J.N., Rapoport, J.L. & Evans, A.C. (1999). Structural maturation of neural pathways in children and adolescents: In vivo study. Science, 283: Friston, K.J., Holmes, A.P., Price, C.J., Büchel, C. & Worsley, K.J. (1999). Multi-subject fmri studies and conjunction analyses. NeuroImage, 10: Cao, J. & Worsley, K.J. (1999). The geometry of correlation fields, with an application to functional connectivity of the brain. Annals of Applied Probability, 9: Cao, J. & Worsley, K.J. (1999). The detection of local shape changes via the geometry of Hotelling s T 2 fields. Annals of Statistics, 27: Worsley, K.J. (1998). Testing for signals with unknown location and scale in a χ 2 random field, with an application to fmri. Advances in Applied Probability, accepted (subject to revision). 13. Worsley, K.J., Cao, J., Paus, T., Petrides, M. & Evans, A.C. (1998). Applications of random field theory to functional connectivity. Human Brain Mapping, 6: Worsley, K.J., Poline, J.B., Friston, K.J. & Evans, A.C. (1998). Characterizing the response of PET and fmri data using Multivariate Linear Models (MLM). NeuroImage, 6:

2 WORSLEY, Keith Fu, L., Matthews, P.M., De Stefano, N., Worsley, K.J., Narayanan, S., Francis, G.S., Antel, J.P., Wolfson, C. & Arnold, D.L. (1998). Imaging axonal damage of normal-appearing white matter in multiple sclerosis. Brain, 121: Worsley, K.J. (1997). An overview and some new developments in the statistical analysis of PET and fmri data. Human Brain Mapping, 5: Poline, J.B., Worsley, K.J., Evans, A.C. & Friston, K.J. (1997). Combining spatial extent and peak intensity to test for activations in functional imaging. NeuroImage, 5: Worsley, K.J., Marrett, S., Neelin, P., Vandal, A.C., Friston, K.J. & Evans, A.C. (1996). A unified statistical approach for determining significant signals in images of cerebral activation. Human Brain Mapping, 4: Worsley, K.J., Marrett, S., Neelin, P. & Evans, A.C. (1996). Searching scale space for activation in PET images. Human Brain Mapping, 4: Poline, J.B., Worsley, K.J., Holmes, A.P., Frackowiak, R.S.J. & Friston, K.J. (1996). Estimating smoothness in statistical parametric maps: Variability of p values. Journal of Computer Assisted Tomography, 19: Worsley, K.J. (1996). The geometry of random images. CHANCE, 9(1): Paus, T., Perry, D.W., Zatorre, R.J., Worsley, K.J. & Evans, A.C. (1996). Modulation of cerebral blood-flow in the human auditory cortex during speech: role of motor-to-sensory discharges. European Journal of Neuroscience, 8(11): Fu, L., Wolfson, C., Worsley, K.J., De Stefano, N., Collins, D.L. & Narayanan, S. (1996). Statistics for investigation of multimodal MR imaging data and an application to multiple sclerosis patients. Nuclear Magnetic Resonance in Biomedicine, 9: e. Actes de colloque (proceeding) (CAC) 24. Worsley, K.J., Liao, C., Grabove, M., Petre, V., Ha, B. & Evans, A.C. (2000). A general statistical analysis for fmri data. NeuroImage, 11:S Andrade, A., Kherif, F., Mangin, J-F., Worsley, K.J., Simon, O., Dehaene, S., Le Bihan, D. & Poline, J-B. (2000). Cortical surface statistical parameteric mapping. NeuroImage, 11:S Chung, M.K., Worsley, K.J., Cherif, C., Paus, T., Collins, D.L., Rapoport, J.L. & Evans, A.C. (2000). Statistical Analysis of Local Volume Change, with an Application to Brain Growth NeuroImage, 11:S Blood, A.J., Petre, V., Worsley, K.J., Pike, G.B. & Zatorre, R.J. (2000). fmri study examining neural correlates of chills in response to subject-selected music. NeuroImage, 11:S Watkins, K.E., Paus, T., Zijdenbos, A., Collins, D.L., Lerch, J.P., Neelin, P., Worsley, K.J. & Evans, A.C. (2000). Detecting structural brain asymmetries using voxel-based morphometry. NeuroImage, 11:S548.

3 WORSLEY, Keith Charil, A., Zijdenbos, A., Boelman, C., Taylor, J., Worsley, K.J., Evans, A.C. & Dagher, A. (2000). Correlation between MS lesions and disability using 3D voxel-based statistical analysis. NeuroImage, 11:S Worsley, K.J., Andermann, M., Koulis, T., MacDonald, D. & Evans, A.C. (1999). Detecting changes in non-stationary images via statistical flattening. NeuroImage, 9:S Ma, L., Worsley, K.J. & Evans, A.C. (1999). Variability of spatial location of activation in fmri and PET CBF images. NeuroImage, 9:S Aston, J.A.D., Worsley, K.J., Bleicher, C., Ma, Y., Gunn, R.N., Evans, A.C. & Dagher, A. (1999). Statistical methods for measuring neurotransmitter release with Positron Emission Tomography. NeuroImage, 9:S Dagher, A., Bleicher, C., Aston, J.A.D., Worsley, K.J. & Evans, A.C. (1998). Measuring neurotransmitter release with Positron Emission Tomography. NeuroImage, 7:S Worsley, K.J., Cao, J., Paus, T., Petrides, M. & Evans, A.C. (1998). Detecting functional connectivity by thresholding correlation random fields. NeuroImage, 7:S Shafie, Kh., Worsley, K.J., Wolforth, M. & Evans, A.C. (1998). Rotation space: Detecting functional activation by searching over rotated and scaled filters. NeuroImage, 7:S Taylor, J., Worsley, K.J., Zijdenbos, A.P., Paus, T. & Evans, A.C. (1998). Detecting anatomical changes using logistic regression of structure masks. NeuroImage, 7:S Worsley, K.J., Wolforth, M. & Evans, A.C. (1998). Scale space searches for a periodic signal in fmri data with spatially varying hemodynamic response. Proceedings of BrainMap 95 Conference, in press. 38. Poline, J.B., Worsley, K.J., Evans, A.C. & Friston, K.J. (1997). Issues in the use of two multivariate analyses for fmri data. NeuroImage, 5:S Cao, J., Worsley, K.J., Liu, C., Collins, L. & Evans, A.C. (1997). New statistical results for the detection of brain structural and functional change using random field theory. NeuroImage, 5:S Kiebel, S.J., Poline, J-B, Holmes, A.P., Worsley, K.J., Frackowiak, R.S.J. & Friston, K.J. (1996). Robust smoothness estimation in statistical parametric maps using residuals from the general linear model. NeuroImage, 3:S Worsley, K.J., MacDonald, D., Cao, J., Shafie, Kh. & Evans, A.C. (1996). Statistical analysis of cortical surfaces. NeuroImage, 3:S MacDonald, D., Worsley, K.J., Avis, D. & Evans, A.C. (1996). Surface segmentation and matching by 3D deformation. NeuroImage, 3:S Poline, J-B., Worsley, K.J., Evans, A.C. & Friston, K.J. (1996). Testing for activations using both signal peak intensity and spatial extent. NeuroImage, 3:S Paus, T., Perry, D.W., Zatorre, R.J., Worsley, K.J. & Evans, A.C. (1996). Modulation of cerebral blood-flow in the human auditory cortex during speech: role of motor-to-sensory discharges. NeuroImage, 3:S452.

4 WORSLEY, Keith 4 h. Liste des participations à des comités de pairs ou d évaluation de la recherche NSERC Statistical Sciences Grant Selection Committee, k. Participation à des comités éditoriaux de revues scientifiques Editorial Board, NeuroImage, Editorial Board, Human Brain Mapping, Editorial Board, CHANCE, h. Participation à l organisation de congrès internationaux Organizer, Workshop on Mathematical Methods in Brain Mapping, CRM Mathematical Methods in Biology and Medicine Year, Montreal, Organizer, Workshop on Statistics of Brain Mapping, CRM Statistics Year, Montreal, Organizing Committee, Fourth International Conference on Functional Mapping of the Human Brain, Montreal, Organizer, ISI Biennial Meeting, Spatial Statistics Session, Turkey, Scientific Program Committee, COMPSTAT 96. p. Prix et bourses qui vous ont été décernés (PRI) Killam Research Fellowship, Statistics of brain mapping, q. Articles soumis Shafie, Kh., Sigal, B., Siegmund, D. & Worsley, K.J. (2001). Rotation space random fields with an application to fmri data. Annals of Statistics, submitted. Worsley, K.J. (2001). Statistical analysis of activation images. In Functional Magnetic Resonance Imaging: An Introductory Guide, Eds. P. Jezzard, P.M. Matthews and S.M. Smith. Oxford University Press. Worsley, K.J. (2001). Gaussian random fields. In Encyclopedia of Environmetrics, Eds. A.H. El-Shaarawi and W.W. Piegorsch. John Wiley and Sons. Chung, M.K., Worsley, K.J., Paus, T., Cherif, C., Collins, D.L., Giedd, J.N., Rapoport, J.L. & Evans, A.C. (2001). A unified statisical approach for deformation based morphometry. NeuroImage, submitted. Chung, M.K., Taylor, J., Worsley, Ramsay, J.O., Robbins, S. & Evans, A.C. (2001). Diffusion smoothing on the cortical surface via the Laplace-Beltrami operator. IEEE Transactions on Medical Imaging, submitted. Worsley, K.J., Liao, C., Aston, J.A.D., Petre, V., Duncan, G.H. & Evans, A.C. (2000). A general statistical analysis for fmri data. NeuroImage, submitted. Liao, C., Worsley, K.J., Poline, J-B., Duncan, G.H. & Evans, A.C. (2000). Estimating the delay and magnitude of the response in fmri data. NeuroImage, (submitted). Worsley, K.J. (1998). Testing for signals with unknown location and scale in a χ 2 random field, with an application to fmri. Advances in Applied Probability, accepted (subject to revision).

5 WORSLEY, Keith 5 Cao, J. & Worsley, K.J. (1998). Applications of random fields in human brain mapping. Proceedings of the workshop on Statistics of Brain Mapping, Centre de Recherche Mathématiques, Université de Montréal, submitted. PRINCIPALES RÉALISATIONS EN RECHERCHE 1. Worsley, K.J. (1998). Testing for signals with unknown location and scale in a χ 2 random field, with an application to fmri. Advances in Applied Probability, accepted (subject to revision). Siegmund & Worsley (1995) considered the problem of testing for signals with unknown location and scale in a Gaussian random field defined on R N. The test statistic was the maximum of a Gaussian random field in an N + 1 dimensional scale space, N dimensions for location and 1 dimension for the scale of a smoothing filter. Scale space is identical to a continuous wavelet transform with a kernel smoother as the wavelet, though the emphasis here is on signal detection rather than image compression or enhancement. Two methods were used to derive an approximate null distribution for N = 2 and N = 3: one based on the method of volumes of tubes, the other based on the expected Euler characteristic of the excursion set. The purpose of this paper is two-fold: to show how the latter method can be extended to higher dimensions, and to apply this more general result to χ 2 fields. The result of Siegmund & Worsley (1995) then follows as a special case. In this paper the results are applied to the problem of searching for activation in brain images obtained by functional magnetic resonance imaging (fmri). 2. Cao, J. & Worsley, K.J. (1999). The detection of local shape changes via the geometry of Hotelling s T 2 fields. Annals of Statistics, 27: This paper is motivated by the problem of detecting local changes or differences in shape between two samples of objects via the non-linear deformations required to map each object to an atlas standard. Local shape changes are then detected by high values of the random field of Hotelling s T 2 statistics for detecting a change in mean of the vector deformations at each point in the object. To control the null probability of detecting a local shape change, we use the recent result of Adler (1998) that the probability that a random field crosses a high threshold is very accurately approximated by the expected Euler characteristic (EC) of the excursion set of the random field above the threshold. We give an exact expression for the expected EC of a Hotelling s T 2 field, and we study the behaviour of the field near local extrema. This extends previous results for Gaussian random fields (Adler, 1981) and χ 2, t and F fields (Worsley, 1994; Cao, 1998). For illustration, these results are applied to the detection of differences in brain shape between a sample of 29 males and 23 females. 3. Cao, J. & Worsley, K.J. (1999). The geometry of correlation fields, with an application to functional connectivity of the brain. Annals of Applied Probability, 9: We introduce two new types of random field. The cross correlation field R(s, t) is the usual sample correlation coefficient for a set of pairs of Gaussian random fields, one sampled at point s R M, the other sampled at point t R N. The homologous correlation field is defined as R(t) = R(t, t), that is, the diagonal of the cross correlation field restricted to the same location s = t. Although the correlation coefficient can be transformed pointwise to a t-statistic, neither of the two correlation fields defined above can be transformed to a t-field, defined as a standard Gaussian field divided by the roit mean square of i.i.d. standard

6 WORSLEY, Keith 6 Gaussian fields. For this reason, new results are derived for the geometry of the excursion set of these correlation fields that extend those of Adler (1981). The results are used to detect functional connectivity (regions of high correlation) in 3D Positron Emission Tomography (PET) images of human brain activity. 4. Worsley, K.J. and Friston, K.J. (2000). A test for a conjunction. Statistics and Probability Letters, 47: A conjunction is defined in the brain mapping literature as the occurrence of the same event at the same location in two or more independent 3D brain images. The images are smooth isotropic 3D random fields of test statistics, and the event occurs when the image exceeds a fixed high threshold. We give a simple approximation to the probability of a conjunction occurring anywhere in a fixed region, so that we can test for a local increase in mean of the images at the same unknown location in all images, a generalization of the split-t test. This is the corollary to a more general result on the expected Minkowski functionals of the set of points where a conjunction occurs. 5. Shafie, Kh., Sigal, B., Siegmund, D. & Worsley, K.J. (2001). Rotation space random fields with an application to fmri data. Annals of Statistics, submitted. Siegmund and Worsley (1995) considered the problem of testing for a signal with unknown location and scale in a Gaussian random field defined on R N. The test statistic was the maximum of a Gaussian random field in an N + 1 dimensional scale space, N dimensions for location and 1 dimension for the scale of a smoothing kernel. Siegmund and Worsley used two methods, one involving the expected Euler characteristic of the excursion set and the other involving the volume of tubes, to derive an approximate null distribution. The purpose of this paper is to extend the scale space result to the rotation space random field when N = 2, where the maximum is taken over all rotations of the filter as well as scales. We apply this result to the problem of searching for activation in brain images obtained by functional magnetic resonance imaging (fmri).