Frontiers in Systems Neuroscience Systems Neuroscience

Abstract

Spike-timing dependent plasticity (STDP) describes the observation that causally related activity (i.e., postsynaptic depolarization following a presynaptic spike within a short latency) leads to strong synaptic potentiation (Bliss and Collingridge, 1993; Markram et al., 1997). In this respect, STDP is a Hebbian learning rule (Caporale and Dan, 2008), and is thus a promising candidate to change the way neurons interact. More recently, similar paradigms have been used in vivo to explore the effect of plasticity within the intact nervous system have all been used to induce Hebbian associations between neurons that are similar to those seen in STDP experiments. As in the in vitro slice preparation, these studies have typically used the magnitude of response to stimulation as the means to evaluate changes in the strength of network connectivity. These studies have provided broad and solid evidence demonstrating that associa-tive mechanisms can cause changes in stimulus-evoked sensory or motor maps. However, moving from the pairwise, stimulus input/output mapping to a measure that represents the functional interactions within a network is difficult. Measuring the strength of every pair-wise stimulus-evoked response becomes rapidly impractical as the size of the network increases. It is also inappropriate theoretically, as the stimulation at any given electrode would inevitably activate many neurons making many different connections than those of