Figure 9.

For 24 neurons, 500 image fragments were presented 10 times each. The graphs show the effects on the response distributions of averaging the responses to the 10 repetitions of each fragment. The abscissas show measures of the distributions of the 5000 individual responses; the ordinates show the equivalent measures of the distributions of the 500 averaged responses. The solid lines are the lines of equality. A, P₀, the probability of obtaining a zero response either to individual stimulus presentations (abscissa) or on average to particular image fragments (ordinate). B, The variance of the distribution of responses divided by the mean response. The overall variance of the distribution is lowered by averaging responses to stimulus repetitions, but the mean response is, of course, unchanged. The dashed line has a slope of 1/10 and shows how much the variance of the response distribution could have been reduced by averaging 10 repetitions, if the whole variety of responses to natural images was attributable to response variability.