(A) Probability of turning the wheel to the correct direction as a function of stimulus contrast in one animal. The probability is computed separately in trial groups of low (blue) and high (cyan) ongoing activity measured in area PM. Error bars indicate 95% binomial confidence intervals. Curves indicate psychometric functions obtained by fitting a probabilistic observer model (Burgess et al., 2017) separately to the two sets of responses. (B) Same as (A), for probability of no-go. (C, D) Same as (A), (B), averaged across mice. Error bars represent S.E. across seven mice. (E) Offset parameter of the perceptual contrast sensitivity function inferred by the model, measured when bilateral activity in PM was low (abscissa) vs. high (ordinate). Symbols indicate parameters from individual animals. Genetic background was Snap25-GCaMP6s (circles), TetO-GCaMP6s;Camk2a-tTA (diamonds) or Vglut1-Cre;Ai95 (squares). (F Same as E), for all visual areas. (G, H) Same as (E), (F), for the scale parameter of the perceptual contrast sensitivity function.