Figure 1.

“High/Low” delayed matched-to-sample space categorization task. (A) Sample trials of the task. After the monkey fixated the red dot, a black task box appeared on a screen in front of the monkey. The vertical position of the box within the screen varied randomly in different trials (B). Following a brief delay, a yellow sample bar was displayed for 1.2 s. Following another brief delay (0.5 s), two green response bars appeared simultaneously on the top and bottom of the task box. After a delay (1.5 s for monkey 1 and 0.8 s for monkey 2), the response bars would flash for 0.8 s in a random sequence, and the monkey had to match the sample bar to the hemi-space corresponding to the flashing bars by pressing simultaneously two foot pedals to receive a juice reward (1). S, sample period; PR, pre-response period; R1 and R2, first and second response periods, respectively. (C) The 10 intermediate heights that were used for the sample bar. A summary of the task epochs is shown in the bottom panel. Eye fixation was required throughout the duration of the trial. The monkeys performed very well in this task (75 and 90% correct for monkey 1 and 2, respectively).