Figure 2.

Influence of the temporal frequency of pairing on STDP. (A) Experiments were performed in the barrel cortex of adult anesthetized rats (see Jacob et al., 2007 for further details). During pairing, a spontaneously emitted action potential triggers a subthreshold deflection of a whisker with a fixed delay (0, 10, 20, or 30 ms). One pairing period contains 400 associations between an action potential and a stimulation of the whisker. (B) The differential change in response (ΔRdiff) defined as the difference between modifications of responses in the paired and the unpaired pathways, is plotted against the mean temporal frequency of the spontaneous action potential discharge during pairing, at short delays (upper plot, −17 < delay < −7 ms) and longer delays (middle plot, delay <−17 ms). A band-pass curve fitted to ΔRdiff for the short-delay pairings (not shown) gives a preferred frequency for the induction of response depression of 2.57 Hz. In the lower two scatter plots, relative changes in response (ΔRdiff) are plotted against the delay of the pairing computed as the imposed delay plus the latency between the stimulation and the arrival of the afferent volley to the cortex. The separation of the pairing population was based on the frequency during the pairing with frequencies between 1.5 and 4.5 Hz (left plot) leading to depression.