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We discuss a biophysical model of synaptic plasticity that provides a unified view of the outcomes of synaptic modification protocols, including: (1) prescribed time courses of postsynaptic intracellular Ca2+ release, (2) postsynaptic voltage clamping with presentation of presynaptic spike trains at various frequencies, (3) direct postsynaptic response to(More)
Experimental observations on synaptic plasticity at individual glutamatergic synapses from the CA3 Shaffer collateral pathway onto CA1 pyramidal cells in the hippocampus suggest that the transitions in synaptic strength occur among discrete levels at individual synapses [C. C. H. Petersen, Proc. Natl. Acad. Sci. USA 85, 4732 (1998); O'Connor, Wittenberg,(More)
Classical type la glycogen storage disease (McKusick 23220) is a severe metabolic disorder caused by a deficiency of the catalytic subunit of the hepatic microsomal glucose-6-phosphatase enzyme. However, it has recently been determined that at least five different polypeptides are required for normal glucose-6-phosphatase activity in vivo (reviewed by(More)
During growth on benzoate-minimal medium Pseudomonas putida mt-2 (PaW1) segregates derivative ('cured') strains which have lost the ability to use the pathway encoded by its resident catabolic plasmid pWW0. Experiments with two plasmids identical to pWW0 but each with an insert of Tn401, which confers resistance to carbenicillin, suggested that the(More)
Uncovering the roles of neural feedback in the brain is an active area of experimental research. In songbirds, the telencephalic premotor nucleus HVC receives neural feedback from both forebrain and brain stem areas. Here we present a computational model of birdsong sequencing that incorporates HVC and associated nuclei and builds on the model of sparse(More)
The telencephalic premotor nucleus HVC is situated at a critical point in the pattern-generating premotor circuitry of oscine songbirds. A striking feature of HVC's premotor activity is that its projection neurons burst extremely sparsely. Here we present a computational model of HVC embodying several central hypotheses: 1) sparse bursting is generated in(More)
The neuroethology of song learning, production, and maintenance in songbirds presents interesting similarities to human speech. We have developed a biophysical model of the manner in which song could be maintained in adult songbirds. This model may inform us about the human counterpart to these processes. In songbirds, signals generated in nucleus High(More)
We have studied 250 human liver biopsy samples to determine the ontogeny of the microsomal glucose-6-phosphatase (EC system. Human hepatic glucose-6-phosphatase enzyme activity develops at 11 weeks' gestation and slowly increases to approximately 10% of adult activity at term. In the first week after birth, activity rises to adult values. Increases(More)