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|Quelle: Sajikumar 2005|
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|1.3.1. Properties of LTP
As a result of brief high frequency stimulation, the LTP expressed in CA3-CA1 synapse of hippocampal region show some basic properties such as ‘inputspecificity’, ‘co-operativity’, ‘associativity’ and ‘late-associativity’ (Bear and Malenka, 1994; Bliss and Collingridge, 1993; Frey and Morris, 1997, 1998; Malenka and Bear, 2004). LTP is input-specific in general, which means those synapses who receive high frequency stimulation only will express LTP. This property of LTP is consistent with its involvement in memory formation. If the activation of one set of synapses leads to the simultaneous activation of all other synapses, even inactive ones, being potentiated, it would be difficult to activate selectively a particular sets of inputs, as is presumably required for learning and memory (Bliss and Collingridge, 1993).
• Bear MF, Malenka RC (1994) Synaptic plasticity: LTP and LTD. Curr Opin Neurobiol 4:38 9[sic]-399.
• Bliss TV, Collingridge GL (1993) A synaptic model of memory: long-term potentiation in the hippocampus. Nature 361:31-39.
• Frey U, Morris RGM (1997) Synaptic tagging and long-term potentiation. Nature 385:533-536.
• Frey U, Morris RGM (1998a) Synaptic tagging: implications for latemaintenance of hippocampal long-term potentiation. Trends Neurosci 21:181-188.
• Frey U, Morris RGM (1998b) Weak before strong: dissociating synaptic tagging and plasticity-factor accounts for late-LTP. Neuropharmacology 37:545-552.
• Malenka RC and Bear MF (2004) LTP and LTD: an embarrassment of riches. Neuron 44:5-21.
|1.4. Basic properties of LTP and LTD
LTP and LTD at the Schaffer collaterals CA1 synapses share several common properties: like input-specificity, co-operativity, associativity and late-associativity (Bliss and Collingridge, 1993;Bear and Malenka, 1994;Malenka and Bear, 2004). LTP/LTD is input-specific, in the sense that it is restricted to the synapses which receive high-frequency stimulation (HFS) or low-frequency stimulation respectively (LFS) (Kelso and Brown, 1986;Lynch et al., 1977). This feature is consistent with its involvement in memory formation. If activation of one set of synapses led to the activation of all other synapses, even inactive ones-being potentiated or depressed, it would be difficult to selectively enhance particular sets of inputs, as is presumably required for learning and memory (Bliss and Collingridge, 1993).
Bear MF, Malenka RC (1994) Synaptic plasticity: LTP and LTD. Curr Opin Neurobiol 4: 389-399.
Bliss TV, Collingridge GL (1993) A synaptic model of memory: long-term potentiation in the hippocampus. Nature 361: 31-39.
Kelso SR, Brown TH (1986) Differential conditioning of associative synaptic enhancement in hippocampal brain slices. Science 232: 85-87.
Lynch GS, Dunwiddie T, Gribkoff V (1977) Heterosynaptic depression: a postsynaptic correlate of long-term potentiation. Nature 266: 737-739.
Malenka RC, Bear MF (2004) LTP and LTD; An Embarrassment of Riches. Neuron 44: 5-21.
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