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Krasnow Institute > Monday Seminars > Abstracts FROM PROTEIN PHOSPHORYLATION TO THE MATRIX OF ASSOCIATION: BUILDING MODELS OF MEMORY FROM BIOCHEMICAL DATA Giorgio Ascoli Laboratory of Adaptive Systems, National Institute for
Neurological Disorders and Stroke, NIH This talk is divided into two fairly independent parts. The first one describes the biochemical work performed to characterize cp20, a neuronal protein causally involved in the cellular mechanisms of learning and memory. Cp20 was discovered in several species' central nervous systems as a molecular correlate of synaptic plasticity. In particular, cp20 inhibits calcium-dependent potassium channels, causing an increased membrane resistance and therefore a hyperexcitability of the neuron (the cellular trace of memory). The protein has been recently cloned, and this allowed a complete characterization of the primary and secondary structure. Cp20 binds calcium and GTP, and it is phosphorylated by the enzyme PKC. The protein undergoes a conformational change upon calcium binding, which seems to be physiologically meaningful. In this talk I will propose a model of the activation pathway involving cp20 and discuss the way biochemical data could be used to build models of neural plasticity. In the second part of the talk, I will introduce a new coordinate system for dendritic spines (the neuronal input gates). This allows the description of the neuron's activity in terms of its biochemical parameters (among which is the conformational status of cp20) with a simple matrix notation. A few properties of this labeling system will be described, and applications to synaptic plasticty problems will be discussed. In particular, biochemical data regarding associative memory can be collected into a matrix describing the interaction among spines. By this method, higher cognitive functions such as abstraction might in principle be described by operators on vector spaces.
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