Input specificity of activity-induced synaptic modification was examined in
the developing Xenopus retinotectal connections. Early in development, lon
g-term potentiation (LTP) induced by theta burst stimulation (TBS) at one r
etinal input spreads to other unstimulated converging inputs on the same te
ctal neuron. As the animal develops, LTP induced by the same TBS becomes in
put specific, a change that correlates with the increased complexity of tec
tal dendrites, and more restricted distribution of dendritic Ca2+ evoked by
each retinal input. In contrast, LTP induced by 1 Hz correlated pre- and p
ostsynaptic spiking is input specific throughout the same developmental per
iod. Thus, input specificity of LTP emerges with neural development and dep
ends on the pattern of synaptic activity.