ACTIVITY-DEPENDENT WIRING OF THE DEVELOPING HIPPOCAMPAL NEURONAL CIRCUIT

In the developing hippocampus, functional excitatory synaptic connecti ons seem to be recruited from a preformed initially silent synaptic ne twork. This functional synapse induction requires presynaptic action p otentials paired with postsynaptic depolarization, thus obeying Hebb's rule of association. During early postnatal development the hippocamp us exhibits an endogenous form of patterned neuronal activity that is driven by GABAergic depolarization. We propose that this recurrent act ivity promotes the input-specific induction of functional synapses in the CA1 region. Thus, activity-dependent synaptic reorganization in th e developing hippocampus appears to be dominated by an active recruitm ent of new synapses rather than an active elimination of redundant con nections.