Hello Yvens,

you can perform STDP measurement in 2-electrode setup with e. g. Keithley 4200 (however it can be done on even on a potentiostat). You have to apply a voltage spike of a given shape, duration and amplitude on the first electrode, followed by the same spike applied on the second electrode. If you measure a current at given voltage before and after such voltage pattern, you will be able to calculate the synaptic weight from the difference between these read currents. Now, you should decrease the interval between the voltage spikes and you should observe an increase or decrease in the current before/after.

To observe both regimes of STDP (potentiation and depression), you should change the sequence of polarizing the electrodes (e.g. to observe potentiation you apply the first pre-synaptic voltage spike on the top electrode and the second post-synaptic spike on the bottom electrode. To observe depression, you should reverse the voltage spike sequence, i.e. the bottom electrode should be polarized first).

You can find additional information in the ESI of our article:

https://pubs.rsc.org/en/content/articlelanding/2019/nr/c8nr09413f

Please note that the STDP shape (Hebbian learning rule) will strongly depend on I-V characteristics of your device and the applied voltage pattern:

https://www.frontiersin.org/articles/10.3389/fnins.2013.00002/full