Figure 6. Responses of On-Center Ganglion Cells in WT and Cx36 KO Retina.

(A) Representative spike trains recorded extracellularly from on-center ganglion cells in WT (left) and Cx36 KO (right) retina to a 500 ms step of full-field illumination of different intensities. Stimulus onset and offset are indicated by the step functions beneath each row of recordings. Both ganglion cells have similar response components, but KO cell is about 100-fold less sensitive than the WT cell.

(B) Normalized responses of WT on-center ganglion cells as a function of light intensity. Each data point shows the average and standard error for a number of cells. The data were fit by Michaelis-Menten equations as described in the Experimental Procedures. Responses fell into four groups: high sensitivity (squares, n = 18), intermediate sensitivity (circles, n = 30), low sensitivity (triangles, n = 9), and wide operating range (diamonds, n = 6). Symbols along the abscissa indicate the response thresholds for each class of cell using a 5% of maximum response criterion.

(C) Normalized responses of KO on-center ganglion cells as a function of stimulus intensity. All KO on-center ganglion cell had response characteristics similar to WT low sensitivity cells. The open square along the abscissa indicates the threshold of cells in the KO. Symbols indicating the thresholds of WT cell classes are provided for comparison.