sponding to the p largest eigenvalues, is transpose of V_p, and X_a is calculated from Eq. 10. A_p is a now smaller but full-rank matrix of eigenimages of X_a. The number p may be taken as the number of eigenvectors required to explain a predetermined proportion of the variance in the original data (e.g., >99%). ICA decomposition of the resulting eigenimages. A_p, gives,

where C_a is the p by n matrix of component maps, and W_E is the computed unmixing matrix.

Substituting for A_p from Eq. 11 gives:

or

whence

giving

since because eigenvectors are mutually orthogonal. Finding the p time courses (of length n) associated with each of the p maps can now be determined by examining the columns of the matrix,

The Heart and Stroke Foundation of Ontario, the Howard Hughes Medical Institute, and the Office of Naval Research supported this research.

1. Friston, K.J. (1996) in Brain Mapping, The Methods, eds. Toga, A.W. & Mazziotta, J.C. (Academic, San Diego), pp. 363–396.

2. Press, W.H., Teukolsky, S.A., Vetterling, W.T. & Flannery, B.P. (1992) Numerical Recipes in C: The Art of Scientific Computing (Cambridge Univ. Press, Cambridge, UK).

3. Bandettini, P.A., Jesmanowicz, A., Wong, E.C. & Hyde, J.S. (1993) Magn. Reson. Med. 30, 161–173.

4. Buckner, R.L., Bandettini, P.A., O’Craven, K.M., Savoy, R.L., Petersen, S.E., Raichle, M.E. & Rosen, B.R. (1996) Proc. Natl. Acad. Sci. USA 93, 14878–14883.

5. Kim, S.G., Richter, W. & Ugurbil, K. (1997) Magn. Reson. Med. 37, 631–636.

6. Friston, K.J., Frith, C.D., Liddle, P.F. & Frackowiak, R.S. (1993) J. Cereb. Blood Flow Metab. 13, 5–14.

7. Gardner, E. (1975) Fundamentals of Neurology (W.B.Saunders, Philadelphia).

8. Friston, K.J., Williams, S., Howard, R., Frackowiak, R.S. & Turner, R. (1996) Magn. Reson. Med. 35, 346–355.

9. Weisskoff, R.M. (1996) Magn. Reson. Med. 36, 643–645.

10. Biswal, B., DeYoe, A.E. & Hyde, J.S. (1996) Magn. Reson. Med. 35, 107–113.

11. Bell, A.J. & Sejnowski, T.J. (1995) Neural Comput. 7, 1129–1159.

12. Bell, A.J. & Sejnowski, T.J. (1997) Vision Res. 37, 3327–3338.

13. Comon, P. (1994) Signal Processing 36, 11–20.

14. Cox, R.W. (1996) Comput. Biomed. Res. 29, 162–173.

15. Bohnen, N., Twijnstra, A. & Jolles, J. (1992) Acta Neurol. Scand. 85, 116–121.

16. Ponsford, J. & Kinsella, G. (1992) J. Clin. Exp. Neuropsychol. 14, 822–838.

17. Bench, C.J., Frith, C.D., Grasby, P.M., Friston, K.J., Paulesu, E., Frackowiak, R.S. & Dolan, R.J. (1993) Neuropsychologia 31, 907–922.

18. McKeown, M.J., Makeig, S., Brown, G.G., Jung, T.-P., Kindermann, S.S., Bell, A.J. & Sejnowski, T.J. (1998) Hum. Brain Mapping, in press.

19. Tulving, E., Markowitsch, H.J., Craik, F.E., Habib, R. & Houle, S. (1996) Cereb. Cortex 6, 71–79.

20. Phelps, E.A., Hyder, F., Blamire, A.M. & Shulman, R.G. (1997) Neuroreport 8, 561–565.

21. Nathaniel-James, D.A., Fletcher, P. & Frith, C.D. (1997) Neuropsychologia 35, 559–566.

22. Manoach, D.S., Schlaug, G., Siewert, B., Darby, D.G., Bly, B.M., Benfield, A., Edelman, R.R. & Warach, S. (1997) Neuroreport 8, 545–549.

23. Nobre, A.C., Sebestyen, G.N., Gitelman, D.R., Mesulam, M.M., Frackowiak, R.S. & Frith, C.D. (1997) Brain 120, 515–533.

24. Binder, J.R. (1997) Clin. Neurosci. 4, 87–94.

25. Friston, K.J., Frith, C.D., Liddle, P.F. & Frackowiak, R.S. (1991) J. Cereb. Blood Flow Metab. 11, 690–699.

26. Lee, T.-W. & Sejnowski, T.J. (1997) Joint Symp. Neural Comput., 4th Institute for Neural Computation, UCSD. 7, 132–140.

27. Girolami, M. & Fyfe, C. (1997) in IEEE International Conference on Neural Networks (Houston, TX), pp. 1788–1791.

Front Matter (R1-R6)

Contents (R7-R8)

The neuroimaging of human brain function (1-2)

Behind the scenes of functional brain imaging: A historical and physiological perspective (3-10)

Event-related functional MRI: Past, present, and future (11-18)

Event-related brain potentials in the study of visual selective attention (19-25)

Functional and structural mapping of human cerebral cortex: Solutions are in the surfaces (26-33)

Imaging neuroscience: Principles or maps? (34-40)

Spatially independent activity patterns in functional MRI data during the Stroop color-naming task (41-48)

Functional analysis of primary visual cortex (V1) in humans (49-55)

The representation of the ipsilateral visual field in human cerebral cortex (56-62)

On the role of selective attention in visual perception (63-68)

Frontoparietal cortical networks for directing attention and the eye to visual locations: Identical, independent, or overlapping neural systems? (69-76)

Neural components of topographical representation (77-84)

The neural development and organization of letter recognition: Evidence from functional neuroimaging, computational modeling, and behavioral studies (85-90)

The effects of practice on the functional anatomy of task performance (91-98)

The acquisition of skilled motor performance: Fast and slow experience-driven changes in primary motor cortex (99-106)

Rapidly induced auditory plasticity: The ventriloquism aftereffect (107-113)

Components of verbal working memory: Evidence from neuroimaging (114-120)

A neural system for human visual working memory (121-128)

Functional neuroimaging studies of encoding, priming, and explicit memory retrieval (129-136)

Anatomy of word and sentence meaning (137-143)

The role of left prefrontal corex in language and memory (144-151)

Neuroimaging studies of word reading (152-159)

Cerebral organization for langague in deaf and hearing subjects: Biological constraints and effects of experience (160-167)