The effects of aging on the bandwidths of directionally-selective mechanisms

Task: Was coherent motion to the right or left? Target dot contrast decreased to obtain a threshold for each notch width (81% performance level using a Quest staircase procedure3) Random dot kinematograms: shown for 0.5 or 0.1s 25 Target dots: moving coherently right (0o) or left (180o). Their direction was randomly selected each trial 475 Notched-noise mask dots: direction of random movement for each dot was independently drawn from a 360o distribution, with the restriction that it was not within 0±n or 180±n degrees (where n is a value in degrees) Notch width (2n) varied from 0 to 179 in separate blocks (2n= 0, 10, 20, 30, 40, 50, 60, 80,120 or 179 degrees)