How Electrodes in salt solution can increase the electric potential

[Lucid Dreamer]

Hello,

I'm not sure if this is the right place for this question, but I am trying to understand how placing electrodes in the brain elicits action potentials.

In a neuron (brain cell), there exists a solution of sodium and potassium ions (among other things). When the brain wants to produce an action potential (electrical spike), the neuron brings in a lot of sodium ions from the outside to make the neuron more positive. It is this positive depolarization that starts an action potential. To artificially simulate this process, we place electrodes on the neuron. My question is how is an electrode able to increase the potential? From what I understand, electrodes can only supply a current of electrons (negatively charged).

EDIT: A lot of papers refer to "injecting current in a cell." I don't understand what that means as you would need an acceptor of electorons within the cell (or a donor)

 

[Borek]

Don't they connect battery to the electrodes?

 

[Lucid Dreamer]

Yeah, it's usually connected to a DC source or battery. But my questions has more to do with the actual mechanism of how electrons in the electrodes can be used to positively or negatively polarize a salt solution

 

[Borek]

Potential difference means there is an electric field present, doesn't matter what is its source.