Figure 9.

Model for STDP at L4-L2/3 synapses. Separate proposed coincidence detectors for LTP and LTD components of STDP. Postsynaptic NMDA receptors are proposed to be the coincidence detector and calcium source for t-LTP (dashed lines). t-LTD induction protocols are proposed to activate the mGluR-VSCC-IP₃R pathway to generate postsynaptic calcium, which drives eCB synthesis, leading to retrograde signaling and presynaptic expression of t-LTD. Non-postsynaptic, potentially presynaptic NMDARs are also required for t-LTD. Whether millisecond scale coincidence detection is performed by the mGluR-VSCC-IP₃R module or by eCB-presynaptic NMDAR signaling is unknown. Whether t-LTP and t-LTD share a common or separate pools of dendritic calcium is also unknown.