### Page Content

### to Navigation

# Functional Imaging Methods: Source Separation Techniques

Optical recording techniques have become a widespread technique for measuring the activity of neural populations. Typically, the optical signal is generated by a mixture of sources, where only some of them are related to the optical signal which is correlated with the neural activity of interest. In addition, the signal-to-noise ratio is often very low, in particular, for single condition maps or and / short recording sequences. In this project we investigated whether recently blind source separation techniques (ICA, extended spatial decorrelation, generalized linear models, etc.) can be properly extended to cope with abovementioned challenges. For optical imaging of intrinsic signals we found, that second order methods based on spatial decorrelation algorithms provided the best results. Methods were applied to optical recording data using intrinsic signals as well as to calcium imaging data.

Acknowledgement: Research was funded by DFG, Wellcome Trust, and Technische Universität Berlin.

### Selected Publications:

Vollgraf, R. and Obermayer, K.
(2006). Quadratic Optimization for Simultaneous Matrix Diagonalization.
*IEEE Trans. Signal Processing Applications*, 54, 3270 – 3278.

Vollgraf, R. and Obermayer, K. (2002). Multi Dimensional ICA to Separate Correlated Sources. *Advances in Neural Information Processing Systems 14*. MIT Press, 993 – 1000.,

Stetter, M., Greve, H., Galizia, C. and Obermayer, K.
(2001). Analysis of Calcium Imaging Signals from the Honeybee Brain by Nonlinear Models.
*Neuroimage*, 13, 119 – 128.

Vollgraf, R., Schießl, I. and Obermayer, K. (2001). Blind Source Separation of Single Components from Linear Mixtures.. *Proc. Int. Conf. on Artificial Neural Networks - ICANN 01*. Springer Berlin Heidelberg, 509 – 514.,10.1007/3-540-44668-0_71

Schießl, I., Schöner, H., Stetter, M., Dima, A. and Obermayer, K. (2000). Regularized Second Order Source Separation. *Int. Workshop on Independent Component Analysis and Blind Signal Separation*, 111 – 116.,

Schießl, I., Stetter, M., Mayhew, J., McLoughlin, N., Lund, J. and Obermayer, K.
(2000). Blind Signal Separation from Optical Imaging Recordings with Extended Spatial Decorrelation.
*IEEE Transactions on Biomedical Engineering*, 47, 573 – 577.

Stetter, M., Schießl, I., Otto, T., Sengpiel, F., Hübener, M., Bonhoeffer, T. and Obermayer, K.
(2000). Principal Component Analysis and Blind Separation of Sources for Optical Imaging of Intrinsic Signals.
*Neuroimage*, 11, 482 – 490.