Charge, Charge Density and Neural Damage

A composite diagram of various studies is shown in this Figure.
The red circle is from cortical stimulation by16 electrodes simultaneously at 15 nC/ph. The Yellow from 16 electrodes interleaved at 4.0 nC/ph. The Green circle from 16 electrodes simultaneously at 1.8 nC/ph.
The dashed red lines plot values of the parameter ‘k’ derived by Shannon (Page 2); The topmost one with k = 1.5, then with k = 0.7 and the lowermost with k = 0.35.
Neural damage was reduced in the operating areas in the lower left part of the plot.