ALL-OR-NONE POTENTIATION AT CA3-CA1 SYNAPSES

The molecular mechanisms underlying longterm potentiation in the hippo campus have received much attention because of the likely functional i mportance of synaptic plasticity for information storage and the devel opment of neuronal connectivity. Surprisingly, it remains unclear whet her activity modifies the strength of individual synapses in a digital (all-or-none) or analog (graded) manner. Here we characterize step-li ke all-or-none transitions from baseline synaptic transmission to pote ntiated states following protocols for inducing potentiation at putati ve single CA3-CA1 synaptic connections. Individual synapses appear to have all-or-none potentiation indicative of highly cooperative process es but different thresholds for undergoing potentiation. These results raise the possibility that some forms of synaptic memory may be store d in a digital manner in the brain.