Quantal analysis and synaptic efficacy in the CNS

Quantal analysis of synaptic transmission at connections between neurons in the CNS has provided insights concerning the structural constraints on transmitter release and postsynaptic responsiveness. However, it has proven difficult in many cases to resolve the size and variability of a single quantum or to distinguish clear peaks in amplitude histograms of evoked responses, due in part to the superposition of background instrumental and biological noise. These limitations raise questions about recent attempts to use direct or indirect methods of quantal analysis in order to distinguish between pre- and postsynaptic loci of the modifications underlying long-term potentiation, particularly since the interpretations are modeldependent and the statistical treatments and experimental techniques employed incorporate simplifying assumptions not yet proven.