Emergence of input specificity of LTP during development of retinotectal connections in vivo

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.