Evidence for associative plasticity in the human visual cortex

Abstract

BackgroundRepetitive convergent inputs to a single post-synaptic neuron can induce long-term potentiation (LTP) or depression (LTD) of synaptic activity in a spike timing-dependent manner. ObjectiveHere we set a protocol of visual paired associative stimulation (vPAS) of the primary visual cortex (V1) in humans to induce persistent changes in the excitatory properties of V1 with a spike timing rule. MethodsWe provided convergent inputs to V1 by coupling transcranial magnetic stimulation (TMS) pulses of the occipital cortex with peripheral visual inputs, at four interstimulus intervals of −50/-25/+25/+50 ms relative to the visual evoked potential (VEP) P1 latency. We analysed VEP amplitude and delayed habituation before and up to 10 min after each vPAS protocol. ResultsVEP amplitude was reduced after vPAS+25. Delayed VEP habituation was increased after vPAS-25 while it was reduced after vPAS+25. ConclusionsWe provide evidence that associative bidirectional synaptic plasticity is a feature not only of the sensorimotor but also of the human visual system.