Associative plasticity at thalamocortical synapses is thought to be constrained by age in the mammalian cortex. However, here we show for the first time that prolonged visual deprivation induces robust and reversible plasticity at synapses between first order visual thalamus and cortical layer 4 pyramidal neurons. The plasticity is associative and expressed by changes in presynaptic function, thereby amplifying and relaying the change in efferent drive to the visual cortex.