Figure 2.
Spike-timing-dependent increase and decrease in corticostriatal synaptic efficacy. A, Representative recording from a single SPN showing spike-timing-dependent LTP. EPSP amplitude, Ri, and Vm are plotted against time. After the baseline period (red line and red EPSP trace, top right inset), stimulation of cortical afferents (“presynaptic stimulation”) was followed 10 ms later by a postsynaptic AP elicited by somatic current injection (see gray inset, Δt = 10 ms). Dashed line indicates average of EPSP amplitudes before the STDP protocol. In the post-pairing time, a 45% increase in EPSP amplitudes was observed (p < 0.0001, blue line and blue trace, top right inset). EPSP traces (top right inset) are averages of all EPSPs recorded in the time indicated by the red and blue lines, respectively. B, Voltage responses to hyperpolarizing and depolarizing current injections (−250 to 175 pA) show inward and outward rectification typical for an SPN (left), and the current–voltage relationship was similar before (red circles) and after (blue circles) EPSP–AP pairing (right; filled circles correspond to voltage responses shown in the left; for simplicity, voltage responses for open circles were not shown in the left). C, Average of all recordings from SPNs that underwent the EPSP–AP pairing with a time delay of Δt = 10 ms (n = 11). Brackets indicate the time when EPSP amplitudes (in percentage of control) were significantly increased compared with baseline (*p < 0.05). For significance tests, EPSP amplitudes were binned in 10 min intervals. D, Representative recording from a single SPN showing spike-timing-dependent LTD. After the baseline period (red line and red trace, top right inset), a somatically induced AP was followed by an EPSP with a delay of Δt = −30 ms (see gray inset). This resulted in a decrease of EPSP amplitudes by 34% (p < 0.0001, blue line and blue trace, top right inset). E, Voltage responses to hyperpolarizing and depolarizing current injections (−375 to 275 pA) are typical for an SPN (left), and the current–voltage relationship is identical before (red circles) and after (blue circles) AP–EPSP pairing. F, Average of all recordings from SPNs that underwent the AP–EPSP pairing with a delay of Δt = −30 ms (n = 12). Brackets indicate the time when EPSP amplitudes were significantly decreased compared with baseline (*p < 0.05).