Figure 2.

Characteristic AP signal recorded with an extracellular microelectrode as the seal resistance is varied. At low R_seal, the amplitude is small and a second derivative behavior is observed (assuming no additional derivative is generated due to the electrode itself). As R_seal increases, the amplitude of the recorded AP signal increases and the order of the derivative decreases. For extremely high R_seal, a whole-cell patch configuration is approached and the intracellular signal is measured.