Figure 3.

Additional synapses can be potentiated by utilizing multiple placements of the rake electrode. The rake electrode was first placed at position A, and baseline EPSPs were measured at each of S1, S2, S3, and S4. Responses were monitored for 30 min after s-HFS delivery at position A, and the % LTP generated at each electrode is tabulated. After ensuring saturation of LTP at this position (by administering second and third s-HFSs and showing that no further potentiation was possible), the rake was repositioned at B and a new baseline was obtained. s-HFS at B potentiated responses above this baseline, and the extent of LTP is quantitated. After saturation was confirmed at B, the electrode was repositioned at C and then at D, and the above tests were repeated. s-HFS was shown to produce comparable levels of LTP at each position, regardless of the prior stimulation received by the slice at other positions. This experiment was repeated and similar results were obtained in a slice from a separate animal.