FIG. 7.

Developmental changes in contrast sensitivity during the onset transient and sustained firing of V1 and V2 neurons. A: analysis methods. PSTHs for responses of an adult V1 complex cell as a function of stimulus contrast. The discharge during a period of 150 ms following the response onset was analyzed for the transient component and the responses during 150 ms at the end of stimulation were analyzed for the sustained component. B: receiver operating characteristic (ROC) curves for the transient (left) and sustained (right) responses of the same cell as a function of contrast. C: probability functions for the transient (left) and sustained (right) component of responses from which threshold (α) and slope (β) values were determined. ···, the probability of 82% correct for determining the threshold value. See the detail in the text. D: representative probability functions of V1 (left) and V2 (right) neurons for 2 (top)- and 4-wk-old (middle) infants and adults (bottom). •, the transient responses; ○, the sustained responses for each unit.