Eyelink 2

Participants were instructed to maintain fixation on a central fixation point throughout each fMRI run. For the experiment involving spiral stimuli, the participant’s eye position was monitored using an MRI-compatible ASL EYE-TRAC eye-tracking system. We applied pattern classifiers to these data to evaluate whether any reliable information about the viewed orientation could be decoded from eye-position signals²² . Analyses of eye movement data during a subset of scans revealed that our ability to decode orientation from eye position was at chance level, t(3)=0.34, p=0.75. We also conducted additional high-resolution measurements of eye position (500 Hz, SR-Research Eyelink II) outside of the MRI scanner for 5 of the subjects that ran in the study, using a visual stimulation paradigm identical to that used in the main attention experiment. We found that when we tried to decode the orientation of a viewed grating based solely on the high-resolution eye tracking data, performance was at chance level, t(4)=1.50, p>0.2. These findings replicate other published results from our lab, in which we attempted to decode stimulus orientation from eye position^{21 ,22 ,43} . Taken together, these results indicate that eye movements are unlikely to have contributed to our ability to classify orientation based on fMRI activity patterns.

Participants were presented with a cover story involving a mother and child looking at a picture book. The mother commented on objects and animals to help the child identify them. Each trial began with presentation of the display. After one second of preview, participants heard a spoken sentence over Sennheiser HD570 headphones and clicked on the referent that best matched the sentence. Eye movements were monitored using a head-mounted SR Research EyeLink II system sampling at 250 Hz, with drift correction procedures performed every fifth trial.