[1] Babraham Inst, Dept Neurobiol, Cambridge CB2 4AT, England
[2] K Human Genome Mapping Project, Resource Ctr, Cambridge CB10 1SB, England
[3] Harvard Univ, Sch Med, Boston, MA 02114 USA
[4] Massachusetts Gen Hosp, Neurol Serv, Boston, MA 02114 USA
[5] Addenbrookes Hosp, Dept Psychiat, Cambridge CB2 2QQ, England