The work was supported in part by the ONR grant N00014-93-1-0335, the NSF grants IRI-9211419 and IRI-9423312, and the NSF equipment grant CDA-9413962. I thank many colleagues who have discussed various aspects and/or critically commented on my earlier writings which led to this chapter, including S. Ahalt, J. Buhmann, S. Campbell, J. Cheyes, B. Ermentrout, P. Holmes, C. Jayaprakash, P. König, N. Kopell, J. Pollack, D. Terman, S. Volman, and C. von der Malsburg.