Lourens Waldorp is assistent professor at the Department of Psychological Methods. His research concerns statistical hypothesis testing, especially in the neurosciences. For example, in fMRI the problem is to cope with thousends of multiple tests without declaring truely nonactive regions active.  In general, many topics in (multivariate) statistics are of interest, like (non)linear regression and asymptotic statistics.

Interests

• graph (network) theory
• graphical models
• network discovery
• mathematical statistics
• applications to biophysical data
• signal processing
  

Teaching

• statistics for first year psychology and beta-gamma students
• multivariate statistics
• Network analysis
• Model selection

Homepage

• home

Publications

refereed journals

• Waldorp, L.J. , Christoffels, I.K., and van de Ven, V. (2010) Effective connectivity of fMRI data using ancestral graph theory: Dealing with missing regions. NeuroImage,54 , 2695-2705.
• Cramer, A. O. J., Waldorp, L. J. , van der Maas, H., & Borsboom, D. Comorbidity: A network perspective. Behavioral and Brain Sciences , (accepted).
• Waldorp, L.J. (2009). Robust and unbiased variance of GLM coefficients for misspecified autocorrelation and hemodynamic response models in fMRI. International Journal of Biomedical Imaging Volume 2009, Article ID 723912.
• Scholte, H. S., Ghebreab, S., Waldorp, L. , Smeulders, A. W. M., and Lamme, V. A. F. (2009). Brain responses strongly correlate with Weibull image statistics when processing natural images. Journal of Vision, 9(4):29, 1-15.
• Weeda, W.D., Waldorp, L.J. , Christoffels, I.K., and Huizenga, H.M.. (2009) Activated region fitting:A robust high power method for fMRI analysis using parameterized regions of activation. Human Brain Mapping,30, 2595-2605.
• Waldorp, L.J. (2008). Brazzale, A. R., Davison, A. C., and Reid, N.: Applied asymptotics: Case Studies in Small Sample Statistics (book review). Biometrics, 64(2) , p. 660.
• Waldorp, L.J. , Huizenga, H.M., Grasman, R.P.P.P., and Molenaar, P.C.M. (2006). Hypothesis testing in distributed source models for EEG and MEG data. Human Brain Mapping, 27(2) , p. 114-128.
• Waldorp, L.J. , Grasman, R.P.P.P., and Huizenga, H.M. (2006). Goodness-of-fit and confidence intervals for approximate models. Journal of Mathematical Psychology, 50 , p. 203-213.
• Waldorp, L.J. , Huizenga, H.M., and Grasman, R.P.P.P. (2005). The Wald test and Cramer-Rao bound in electromagnetic source analysis. IEEE Transactions on Signal Processing, 53(9) , p. 3427-3435.
• Waldorp, L.J. , Huizenga, H.M., Nehorai,A., Grasman, R.P.P.P., and Molenaar, P.C.M. (2005). Model selection in spatio-temporal electromagnetic source analysis. IEEE Transactions on Biomedical Engineering, 52(3) , p. 414-220.
• Grasman, R.P.P.P., Huizenga, H.M. Waldorp, L.J. , Molenaar, P.C.M., and Bocker, K.B.E. (2005). Stochastic maximum likelihood mean and cross spectrum structure modelling in neuromagnetic source estimation. Digital Signal Processing, 15(1) , p. 5672.
• Grasman, R.P.P.P., Huizenga, H.M. Waldorp, L.J. , Bocker, K.B.E., and Molenaar, P.C.M. (2004). Frequency Domain Simultaneous Source and Source Coherence Estimation With an Application to MEG. IEEE Transactions on Biomedical Engineering, 51(1) , p. 4555.
• Christoffels, I.K., De Groot, A.M.B., and Waldorp, L.J. (2003). Basic skills in a complex task: A graphical model relating memory and lexical retrieval to simultaneous interpreting. Bilingualism: Language and Cognition, 6(3) , p. 201-211.
• Waldorp,L.J. , Huizenga, H.M., Grasman, R.P.P.P., Bocker, K.B.E., de Munck, J.C., and Molenaar, P.C.M. (2002). Model selection in electromagnetic source analysis with an application to VEFs. IEEE Transactions on Biomedical Engineering, 49 , p. 737-741.
• Huizenga, H.M., de Munck, J.C., Waldorp, L.J. , and Grasman, R.P.P.P. (2002). Spatiotemporal EEG/MEG source analysis based on a parametric noise covariance model. IEEE Transactions on Biomedical Engineering 49(6) , p. 533-539.
• de Munck, J.C., Huizenga, H.M., Waldorp, L.J. , and Heethaar, R.M. (2002). Estimating stationary dipoles from MEG/EEG data contaminated with spatially and temporally correlated background noise. IEEE Transactions on Signal Processing, 50(7) , p. 1565-1572.
• Waldorp, L.J. , Huizenga, H.M., Dolan, C.V., and Molenaar, P.C.M. (2001). Estimated generalized least squares electromagnetic source analysis based on a parametric noise covariance model. IEEE Transactions on Biomedical Engineering 48 , p. 737-741.
• Phaf, R.H., Christoffels, I.K., Waldorp, L.J. , and den Dulk, P. (1998). Connectionist investigations of individual differences in stroop performance. Perceptual and Motor Skills 87 , p. 899-914.

• L.J. Waldorp , H.M. Huizenga, A. Nehorai, R.P.P.P. Grasman, and P.C.M. Molenaar (2004). Model selection in spatio-temporal electromagnetic source analysis. In: Biomag2004, Proc. 14th Int. Conf. on Biomagnetism , E. Halgren, S. Ahlfors, M. Hamalanen, D. Cohen eds. (Boston, Massachusetts, USA, 2004), p. 188-189.
• L.J. Waldorp , H.M. Huizenga, R.P.P. Grasman, J.C. de Munck, K.B.E. Bocker, and P.C.M. Molenaar (2002). Model selection in electromagnetic source analysis. In: Biomag2002, Proc. 13th Int. Conf. on Biomagnetism , J. H. Nowak, J. Haueiesen, F. Gießler, R. Huonker eds. (Univ. of Jena, Jena, Germany, 2002), p. 807-809.
• R.P.P.P. Grasman, L.J. Waldorp , H.M. Huizenga, K.B.E.Bocker, and P.C.M. Molenaar (2002). Frequency domain source and source coherence analysis. In: Biomag2002, Proc. 13th Int. Conf. on Biomagnetism , J. H. Nowak, J. Haueiesen, F. Gießler, R. Huonker eds. (Univ. of Jena, Jena, Germany, 2002), p. 751-753.
• H.M. Huizenga, R.P.P. Grasman, L.J. Waldorp , J.C. de Munck, K.B.E. Bocker, and P.C.M. Molenaar (2002). Analysis of EEG/MEG sources and their lagged covariances. In: Biomag2002, Proc. 13th Int. Conf. on Biomagnetism , J. H. Nowak, J. Haueiesen, F. Gießler, R. Huonker eds. (Univ. of Jena, Jena, Germany, 2002), p. 825-828.
• J.C. de Munck, F. Bijma, H.M. Huizenga, L.J. Waldorp , and R. Heethaar (2002). Spatial and temporal correlations in MEG/EEG background noise. In: Biomag2002, Proc. 13th Int. Conf. on Biomagnetism , J. H. Nowak, J. Haueiesen, F. Gießler, R. Huonker eds. (Univ. of Jena, Jena, Germany, 2002), p. 819-821.
• K.B.E. Bocker, L.J. Waldorp , R.P.P. Grasman, J.C. de Munck, J.L. Kenemans, and H.M. Huizenga (2002). Estimating the number of sources in a VEF/MRI study. In: Biomag2002, Proc. 13th Int. Conf. on Biomagnetism , J. H. Nowak, J. Haueiesen, F. Gießler, R. Huonker eds. (Univ. of Jena, Jena, Germany, 2002), p. 454-456.
• L.J. Waldorp , H.M. Huizenga, C.V. Dolan, R.P.P.P. Grasman, and P.C.M. Molenaar. (2000). Maximum likelihood estimation with a parametric noise covariance model for instantaneous and spatio-temporal electromagnetic source analysis. In: M. Viberg (ed.) Proceedings of the 2000 IEEE Sensor Array and Multichannel Signal Processing Workshop . Cambridge: Springer-Verlag.
• L.J. Waldorp , H.M. Huizenga, R.P.P.P. Grasman, and P.C.M. Molenaar (2000). Model selection procedures in electromagnetic source analysis. In: Biomag2000, Proc. 12th Int. Conf. on Biomagnetism , J. Nenonen, R.J. Ilmoniemi, and T. Katila, eds. (Helsinki Univ. of Technology, Espoo, Finland, 2001), p. 693-696.
• H.M. Huizenga, L.J. Waldorp , and R.P.P.P. Grasman (2000). Maximum likelihood spatiotemporal electromagnetic source analysis. In: Biomag2000, Proc. 12th Int. Conf. on Biomagnetism , J. Nenonen, R.J. Ilmoniemi, and T. Katila, eds. (Helsinki Univ. of Technology, Espoo, Finland, 2001), p. 721-724.
• R.P.P.P. Grasman, H.M. Huizenga, P.C.M. Molenaar, and L.J. Waldorp . (2000). Electromagnetic source localization and interactions between neural generators. In: Biomag2000, Proc. 12th Int. Conf. on Biomagnetism , J. Nenonen, R.J. Ilmoniemi, and T. Katila, eds. (Helsinki Univ. of Technology, Espoo, Finland, 2001), pp. 738-741.

• Waldorp, L.J. , Christoffels, I.K., and Van de Ven, V. (2009). Modelling functional and effective connectivity simultaneously with possible unobserved areas in fMRI. Human Brain Mapping (in press).
• L.J. Waldorp , R.P.P.P Grasman, W.D. Weeda, H.M. Huizenga (2006). Robust latency testing in fMRI. NeuroImage, S.
• L.J. Waldorp , H.M. Huizenga, R.P.P.P. Grasman, and E. Formisano. Using the sandwich estimate for reliable covariance of coefficients and hypothesis testing in fMRI with temporally correlated residuals, NeuroImage, 26 , S41.
• L.J. Waldorp , H.M. Huizenga, and P.C.M. Molenaar (2001). Goodness of fit measures in electromagnetic source analysis. (ISBET2000) Brain Topography , 13(3), p. 246.
• H.M. Huizenga, L.J. Waldorp , and R.P.P.P. Grasman (2001). Maximum likelihood spatiotemporal source analysis. (ISBET2000) Brain Topography, 13(3) , p. 235.
• J.C. de Munck, H.M. Huizenga, L.J. Waldorp , and R. Heethaar (2001). Estimating stationary dipoles from MEG/EEG data contaminated with spatially and temporally correlated background noise. NeuroImage, 13 (6) , S109.
• L.J. Waldorp , C.V. Dolan, and H.M. Huizenga (2000). A parametric model of noise covariances for GLS electromagnetic source analysis. Journal of Psychophysiology, 14(4) , 266-267.

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