FIG. 10.

Contrast discriminability of transient and sustained discharge. A: discriminability vs. slope constant (β) values. Two units (black and blue) had the same α value (0.12) but different β values (2.39 and 6.39). Their discriminability values, defined as the increase in detection probability caused by 1.0% increment in stimulus contrast at the steepest portion of each function (right small panels) were same as their β values (2.39 and 6.39, respectively). Two units (black and orange) had the same β value (2.39) but their α values were considerably different (0.12 and 0.42). Consequently, their contrast discriminability values were also very different (2.39 and 0.68). B: scatter plots of discriminability values for the transient responses of V1 (left) and V2 (right) units against discriminability values for their sustained responses in 2 (top)- and 4-wk-old (middle) infants and adults (bottom). Frequency histograms and median values (▾) are also illustrated.