Above. The normalized change in membrane current was plotted against the light intensity during the decrement (i.e., the 'step-to' light intensity with the result that larger decrements are plotted toward the left). Current was normalized by setting the average immediately before a decrement equal to 0 relative to the resting current, 1, in the dark. Normalized steady cb1b and cb2 responses were significantly different during all decrements (mean +/- S.E.). Upper middle. Change in response variance, before versus during a decrement, is plotted against 'step-to' light intensity. Hash marks denote either negative change or no change (Levene's Mean Statistic). Lower middle. Effective unit amplitude was calculated by separately analyzing each of the 3 trials and plotted against light 'step-to' intensity (open circles are mean +/- S.E. while closed circles show individual data points). Hash marks denote n.s. difference from 0 (two-tailed one sample t test). Below. Aggregate unitary responses for 11 cb2 and 4 cb1a/b BCs independently recorded. Asterisks indicate that the values of the cb1 cell unit were significantly reduced during decrements 1-3 relative to decrement 5. See Statistics and Reproducibility for additional p values and criteria.
