Past and present research supported in part by the NSF (DMS 0505424, 0805798, 1106772, 1159005, 1521551, 1646108, 1916222, 2052918, 2210439), NIH (R01-MH-130348-01, 1-R01-MH123458,  5-R21-DA045146, 5-R01-AR05664603, 1-R21-DA045146), ONR (N000141612910), NSA (MSPF-04Y-120), and the Dana Foundation. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation, the National Institutes of Health, the Office of Naval Research, the National Security Agency, and the Dana Foundation.