Figure 4
From: Aging affects gain and internal noise in the visual system

The correlations between contrast sensitivity and the gain of perceptual template at all spatial frequencies at low, medium and high noise levels for the young and old group, respectively. Data from all observers were pooled. āYā denotes the young group; āOā denotes the old group; āLowā: low noise level; āMediumā: medium noise level; āHighā: high noise level.