Figure 1.

Experimental setup and task sequence. A, Scheme of the setup used for the fixation-in-depth task in one monkey. Exact distances are indicated in the lateral view (left) and top views (right). The monkey was fixating in darkness one of the nine LEDs embedded in a panel located at eye level. B, Time course of the task. A typical example of the version (top) and vergence (bottom) traces during a single trial is shown. Long vertical continuous lines indicate the occurrence of task and behavioral markers. From left to right markers show the following: trial start (home button, HB press), target appearance (LED light on green, LED on), LED change (green to red change of the LED), and trial end (home button, HB release). The long vertical dashed line indicates the end of the saccade, as detected in the off-line analysis. The squares under eye traces indicate the approximate duration of epochs FREE and FIX (see Materials and Methods).