Acknowledgements
The authors thank Anatoly Rinberg for supplying the CsCl data. FG is supported by the Swiss National Science Foundation (SNSF, 200020-132871). EM and GJG are supported by NIH grant MH 46742, and TK is supported by NIH grant F32 NS099590. UE is supported by NSF grant IIS 0643993 and NINDS grant R01 NS073118. MK and UE acknowledge joint support by NINDS grant R01 NS072023.