Department of Mathematics and Statistics, Boston University, Boston, Massachusetts, United States of America.|Department of Mathematics and Statistics, Boston University, Boston, Massachusetts, United States of America.|Department of Theoretical Neuroscience, Bernstein Center for Computational Neuroscience, Central Institute of Mental Health, Heidelberg University, Mannheim, Germany.|Department of Psychological and Brain Sciences, Center for Systems Neuroscience, Boston University, Massachusetts, United States of America.|Department of Mathematics and Statistics, Boston University, Boston, Massachusetts, United States of America.