This application is for continued support of the administrative and research cores of the BF Stolinsky Laboratories Mental Retardation Research Center at the University of Colorado Health Sciences Center. This MRRC began its operations in 1968, and the name and most of its researchers and cores have recently moved to a new and larger facility on the UCHSC campus. The research of the ten investigators that utilize the cores impacts substantially on mental retardation and developmental disabilities. Most of this work is on inherited causes of central nervous system dysfunction, with a primary focus on inborn errors of metabolism and specifically on disorders of mitochondria. Substantial effort is also directed to environmental causes of MRDD, including trace metal deficiencies and viral infections, and to how these conditions affect cognitive development. Studies on inherited metabolic causes of central nervous system dysfunction focus on glutaric acidemia types I and II (Goodman & Frerman), cystathionine beta-synthase deficiency (Kraus), and disorders of the mitochondrial respiratory chain (Frerman, Howell, Parker); the primary aim of these studies is to better understand pathogenesis, so that efforts to treat can have a more logical basis. Studies of environmental causes of MRDD examine the impact of zinc deficiency in infancy and during gestation (Hambidge), and latent viral infections in the newborn period (Crnic) on subsequent cognition. Other studies focus on the neuropsychology of developmental learning disorders, in particular dyslexia, attention deficit hyperactivity disorder, and autism (Pennington); the phenotype of fragile-X syndrome (Hagerman); early events in neuronal development of the human CNS (Pfenninger); and neuromuscular defects related to sodium channels (Caldwell). Core facilities for which support is sought include (a) administration, (b) cell biology (tissue culture and molecular biology), (c) enzyme and molecular diagnosis, (d) chemistry/mass spectrometry, (e) developmental neuropsychology, (f) animal housing and assessment, (g) instrument maintenance and (h) glassware washing services. Core (c) is new to this application.