An effect of context on saccade-related behavior and brain activity.

The present study evaluated the effect of context on behavior and brain activity during saccade tasks. FMRI and eye movement data were collected while 36 participants completed three runs in a block design: (1) fixation alternating with pro-saccades, (2) fixation alternating with anti-saccades, and (3) pro- alternating with anti-saccades. Two task-related data-driven regressors, identified using independent component analysis, were used in GLM analyses. Brain activity associated with anti- and pro-saccades were compared under both single (runs 1 and 2) and mixed saccade (run 3) conditions. Brain areas consistently associated with anti-saccades in previous studies, including striatum, thalamus, cuneus, precuneus, lateral and medial frontal eye fields (FEF), supplementary eye fields (SEF), and prefrontal cortex (PFC) showed significantly greater percent signal change during the fixation/anti- compared with the fixation/pro-saccade run. During the pro/anti run, however, only precuneus, SEF and FEF showed greater activation during the anti-saccade trials. This is a clear demonstration that the saccade-related neural circuitry is affected by context. Behavioral results suggest that performance on saccade tasks is also affected by context. Participants made more direction errors on pro-trials that followed anti-trials than on pro-trials that followed fixation. Results from this study indicate that precuneus, SEF and FEF, which showed anti-saccade-related activity during both comparisons, may be more important for supporting this complex behavioral response. Other brain regions, such as PFC, however, which showed anti-saccade-related activity during only the single task comparison, may be more involved in response selection and/or context updating.