Figure 1. Schematic of experimental design and statistical comparisons.

A) Subjects tracked the location of a red asterisk on the corners of a black diamond (up, down, right, left), and had to indicate whether the location of the current stimulus (*) matched the location of the target. In the 0-back condition, the subject indicated whether the stimulus was located at the top of the diamond (target-up position). B) We performed a general linear model with the following factors: 1) patients vs. controls, 2) threat vs. safe, and 3) load. We modeled the load factor using the three orthogonal planned comparisons depicted.