Figure 5

Scheme of a two-pathway LTP experiment performedusing MEA 5 × 13 3D MEAs. A) A hippocampal slice was placed over a 5 × 13 3D MEA and a suitable principal recording electrode (red circle) was selected in the proximal part of stratum radiatum. Control (blue circle) and test (yellow circle) stimulation electrodes were then chosen on the basis of their pathway independence and distance to the principal recording electrode (usually ≥ 400 μm). Layers of cell bodies in the hippocampal slice are delineated by dashed lines. Distance between electrodes is 140 and 200 μm. B) Alternating stimulation of control and test pathways was performed at baseline stimulus strength that elicited 40% of the maximum fEPSP (first column of traces). After 30 min of stable baseline recording, HFS of the test pathway was performed by two trains of 100 stimuli given at 100 Hz each with inter-train interval of 50 s (trace in the second column). Third column depicts fEPSP recordings 60 min after LTP induction. As follows from overlaid baseline (black) and post-LTP (red) traces in the fourth column, fEPSP amplitude in the test pathway was enhanced, whereas control fEPSPs did not change. C) Plot of fractional fEPSP amplitudes in the control and test pathways before and after LTP induction.