It was previously shown

that a brief period of this “dual-whisker experience” (DWE) causes the cortical representations of the two spared whiskers to overlap with one another (Diamond et al., 1994). We found that STD-LTP could be efficiently induced in the naive barrel cortex, but only by the PW and not by SW deflections. DWE induced a disinhibition of SW-evoked responses and facilitated surround STD-LTP. To study if STD-LTP could serve as a mechanism for sensory-driven response potentiation in the barrel cortex, we performed whole-cell recordings of supragranular pyramidal cells in vivo in one barrel column while repeatedly combining deflections of either the PW or SW with intracellular current injections. Prior to the whole-cell recordings, the C1 and C2 barrel columns were identified using IWR-1 in vitro intrinsic optical signal imaging (Figure 1A; see Figures S1A–S1C available online). Under anesthesia, regular spiking layer (L) 2/3 pyramidal cells in the C2 barrel column were blindly patched (Figure 1B). Consistent with previous findings, deflections of the PW (C2) or SW (C1)

evoked compound PSPs with variable amplitudes (Brecht et al., 2003; Wilent and Contreras, 2004) (Figures 1C and S1D–S1K). To facilitate comparisons of PSPs under different conditions, further analysis was confined to the peak amplitudes and integrals within 40 ms after whisker deflection, and only if PSPs arose during membrane potential down states (for details see Experimental Procedures; Figures S1D–S1K). PW-evoked PSPs had slightly shorter onset latencies

(PW, 10 ± 0.5 ms; SW, 11.3 ± 0.5 ms, n = 20; p < 0.001; Figure 1D), selleck products higher peak amplitudes (PW, 9.2 ± 1.3mV; SW, 5.4 ± 0.8mV, n = 20; p < 0.001; Figure 1E), and larger integrated potentials (PW, 199 ± 32mV×ms; SW, 124 ± 21mV×ms, n = 20; p < 0.001; Figure 1E) aminophylline as compared to SW responses (Armstrong-James et al., 1992; Brecht et al., 2003). To induce STD-LTP, we applied a classical AP-PSP-pairing protocol (Jacob et al., 2007; Markram et al., 1997). After a 5–10 min baseline recording, whisker-evoked PSPs were paired with suprathreshold current injections for 3–5 min (0.667 Hz). Current injections induced short AP bursts (2.7 ± 0.8 [SD] spikes/burst, n = 54; Figures 2A and S2A–S2C) and were timed in such a way that they followed the PSP onset. The spike-time delay was defined as the difference between the average latency of the first AP, as measured over the pairing period, and the average PSP onset latency, as measured over the baseline period (Δ delay; Figures 2A and S2A–S2C). We aimed at pairing both responses with Δ delays of less than 15 ms, which is a typical window for STD-LTP (Feldman, 2000; Markram et al., 1997). We analyzed the level of LTP as an average over the cell population as well as in individual cells. Pairing of PW-evoked PSPs with APs induced, on average, a long-lasting (24.1 ± 1.