[1] Harvard Univ, Dept Psychol, Cambridge, MA 02138 USA
[2] Univ Calif San Francisco, Dept Psychiat, San Francisco, CA 94143 USA
[3] VA Med Ctr San Francisco, Dept Psychiat, San Francisco, CA 94143 USA
[4] Univ Calif Berkeley, Helen Wills Neurosci Inst, Berkeley, CA 94720 USA