RT Journal Article SR Electronic T1 Developmental Switch in Spike Timing-Dependent Plasticity at Layers 4–2/3 in the Rodent Barrel Cortex JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 15000 OP 15011 DO 10.1523/JNEUROSCI.2506-12.2012 VO 32 IS 43 A1 Chiaki Itami A1 Fumitaka Kimura YR 2012 UL http://www.jneurosci.org/content/32/43/15000.abstract AB Sensory deprivation during the critical period induces long-lasting changes in cortical maps. In the rodent somatosensory cortex (S1), its precise initiation mechanism is not known, yet spike timing-dependent plasticity (STDP) at layer 4 (L4)–L2/3 synapses are thought to be crucial. Whisker stimulation causes “L4 followed by L2/3” cell firings, while acute single whisker deprivation suddenly reverses the sequential order in L4 and L2/3 neurons in the deprived column (Celikel et al., 2004). Reversed spike sequence then leads to long-term depression through an STDP mechanism (timing-dependent long-term depression), known as deprivation-induced suppression at L4–L2/3 synapses (Bender et al., 2006a), an important first step in the map reorganization. Here we show that STDP properties change dramatically on postnatal day 13–15 (P13–P15) in mice S1. Before P13, timing-dependent long-term potentiation (t-LTP) was predominantly induced regardless of spiking order. The induction of t-LTP required postsynaptic influx of Ca2+, an activation of protein kinase A, but not calcium/calmodulin-dependent protein kinase II. Consistent with the strong bias toward t-LTP, whisker deprivation (all whiskers in Row “D”) from P7–P12 failed to induce synaptic depression at L4–L2/3 synapses in the deprived column, but clear depression was seen if deprivation occurred after P14. Random activation of L4, L2/3 cells, as may occur in response to whisker stimulation before P13 during network formation, led to potentiation under the immature STDP rule, as predicted from the bias toward t-LTP regardless of spiking order. These findings describe a developmental switch in the STDP rule that may underlie the transition from synapse formation to circuit reorganization at L4–L2/3 synapses, both in distinct activity-dependent manners.