Event-related fMRT during Saccadic Gap- and Overlap-Paradigms: Neural Correlates of Express Saccades

Abstract

Saccadic latencies below 130 ms can occur in the so-called gap paradigm, in which a central fixation point is extinguished approx. 200 ms prior to the occurrence of a left- or right-sided target. These “express” saccades are thought to reflect endogenous processes related to the prior release of attention thereby enhancing a rapid lateral shift to the saccadic target. Using an event-related fMRI approach we studied the BOLD correlates of saccadic control in the gap paradigm (yielding 70% express saccades) to that found in the overlap paradigm (yielding 6% express saccades). The results of 8 subjects indicate significantly (SPM2) more pronounced activation in subcortical structures in the gap paradigm. In the comparison between the overlap and gap paradigms more activation was found in left dorsolateral prefrontal cortex, right posterior parietal cortex and bilateral temporal cortex during the overlap task. The findings suggest that express saccades are associated with less cortical, and more subcortical, activation.

Deutsche Forschungsgemeinschaft: SFB 517, C9