"Proceedings of four symposia held at the University of Pennsylvania on October 15-18, 1980 ... the William W. Chambers and C.N. Liu Symposium on Plasticity in the Mammalian Nervous System; the James M. Sprague Symposium on Changing Concepts of Central Visual System Organization; the Eliot Stellar Symposium on the Neuropsychology of Motivation; the Louis B. Flexner Symposium on Memory"--Preface