[1] Univ Cambridge, Brain Mapping Unit, Cambridge CB2 2QQ, England
[2] Univ Cambridge, Behav & Clin Neurosci Inst, Cambridge CB2 2QQ, England
[3] CNRS, UMR 5216, GIPSA Lab, Grenoble, France
[4] NIMH, NIH, Bethesda, MD 20892 USA
[5] Univ Cambridge, Cavendish Lab, Dept Phys, Cambridge CB3 0HE, England