Current-source density analysis of the electroretinogram of the frog: methodological issues and origin of components.

The technique of current-source density (CSD) analysis for extracellular potentials is reviewed, along with some methodological features that are important for performing CSD analysis of the electroretinogram. In addition, three formulas for computing CSD's are examined on model circuits of resistors and current generators. Finally, CSD results from frog retina that bear on the origins of the b, d, and M waves, along with slow PIII, are presented. It is concluded that the b and d waves are generated primarily and directly by bipolar cells, whereas the M wave and the slow PIII are generated by Müller (glial) cells through the K+ spatial buffer mechanism.