INFORMATION-PROCESSING WITH FREQUENCY-DEPENDENT SYNAPTIC CONNECTIONS

The efficacy of synaptic transmission between two neurons changes as a function of the history of previous activations of the synaptic conne ction. This history dependence can be characterized by examining the d ependence of transmission on the frequency of stimulation. In this fra mework synaptic plasticity can also be examined in terms of changes in the frequency dependence of transmission and not merely in terms of s ynaptic strength which constitutes only a linear scaling mechanism. Re cent work shows that the frequency dependence of transmission determin es the content of information transmitted between neurons and that syn aptic modifications can change the content of information transmitted. Multipatch-clamp recordings revealed that the frequency dependence of transmission is potentially unique for each synaptic connection made by a single axon and that the class of pre-postsynaptic neuron determi nes the class of frequency dependence (activity independent), while th e unique activity relationship between any two neurons could determine the precise values of the parameters within a specific class (activit y dependent). The content of information transmitted between neurons i s also formalized to provide synaptic transfer functions which can be used to determine the role of the synaptic connection within a network of neurons. It is proposed that deriving synaptic transfer functions is crucial in order to understand the link between synaptic transmissi on and information processing within networks of neurons and to unders tand the link between synaptic plasticity and learning and memory. (C) 1998 Academic Press.