Figure 8.

Schematic illustration of the mechanisms underlying pathway-specific LTP at an excitatory synapse onto perisomatic inhibitory interneurons. Repeated coactivation of PP and MF inputs converging onto a postsynaptic PII with a disynaptic latency of ∼10 ms induces LTP at MF synapses. LTP requires CP-AMPARs that are selectively expressed at MF–PII terminals. In contrast, PP–PII synapses express predominantly CI-AMPARs and do not show LTP in our experiments. Synaptic plasticity at MF–PII synapses leads to enhanced recruitment of PIIs and, thereby, an increased feedback inhibition in the DG circuitry, an important requirement for maintaining sparse activity in the principal cell population and a high signal-to-noise ratio in information processing. See text for additional details. The traces represent average EPSPs and single action potentials.