Is Net Synapse Formation a Correlate of Learning?
Neural activity plays an important role in the emergence of new spines, the stabilization of existing spines, and changes in spine morphology. However, the extent to which dendritic motility depends on afferent innervation or synaptic activity is under debate. Much of this debate centres on the use of a cellular model of learning-long-term potentiation (LTP). The essence of LTP is a remarkably persistent enhancement of synaptic responses resulting from brief, repetitive activation of an excitatory afferent monosynaptic pathway by high frequency trains of electrical impulses.11 LTP has been studied most intensively at excitatory hippocampal synapses formed by Schaffer collaterals on CA1 pyramidal cells or by perforant path fibres on dentate gyrus granule cells. Recently developed imaging techniques that permit time-lapse observations have allowed an unprecedented understanding of dendritic spine dynamics. Studies using coordinated patterns of activity, such as the tetanic stimulation re
