[1] MIT, DIV HLTH SCI & TECHNOL, 77 MASSACHUSETTS AVE, CAMBRIDGE, MA 02139 USA
[2] YALE UNIV, DEPT PHARMACOL, NEW HAVEN, CT 06520 USA
[3] YALE UNIV, DEPT PSYCHIAT, NEW HAVEN, CT 06520 USA
[4] MIT, WHITAKER COLL HLTH SCI TECHNOL & MANAGEMENT, CAMBRIDGE, MA 02139 USA
[5] MIT, DEPT CHEM ENGN, CAMBRIDGE, MA 02139 USA
[6] MIT, DEPT BRAIN COGNIT SCI, CAMBRIDGE, MA 02139 USA
[7] UNIV MUNICH, SCH MED, INST MED PSYCHOL, D-8000 MUNICH 2, FED REP GER