In search of a reliable electrophysiological marker of oculomotor inhibition of return

Abstract

Inhibition of return (IOR) operationalizes a behavioral phenomenon characterized by slower responding to cued, relative to uncued, targets. Two independent forms of IOR have been theorized: input-based IOR occurs when the oculomotor system is quiescent, while output-based IOR occurs when the oculomotor system is engaged. EEG studies forbidding eye movements have demonstrated that reductions of target-elicited P1 components are correlated with IOR magnitude, but when eye movements occur, P1 effects bear no relationship to behavior. We expand on this work by adapting the cueing paradigm and recording event-related potentials: IOR is caused by oculomotor responses to central arrows or peripheral onsets and measured by key presses to peripheral targets. Behavioral IOR is observed in both conditions, but P1 reductions are absent in the central arrow condition. By contrast, arrow and peripheral cues enhance Nd, especially over contralateral electrode sites.

Keywords: Cueing; Event-related potentials; Eye movements; Inhibition of return; Oculomotor activation; Sensory and motor processing.

Figure 1

Sequence of events in a sample trial. Although uninformative about the location of the upcoming peripheral target, the cue (whether central or peripheral) called for a saccade to the indicated peripheral box, and participants were instructed to saccade back to the original fixation as quickly as possible. The target appears at the cued (and recently fixated) location.

Figure 2

Target-elicited ERP waveforms and topographic maps for the central cue condition recorded from ipsilateral and contralateral parieto-occipital electrodes (PO7/8; indicated as solid black dots in the topographic maps). Time windows in the ERP plots indicate the windows used to calculate ERP component amplitudes (see text for details). Time windows with a solid outline represent significant differences between cued and uncued ERP components (t tests, p < .05); for central cueing, only the Nd component showed a cueing effect, for both ipsilateral and contralateral electrodes. Topographic heat maps associated with each time window/ERP component for targets appearing on the left and right sides are presented, with red indicating most positive activation and blue indicating most negative activation.

Figure 3

Target-elicited ERP waveforms and topographic maps for the peripheral cue condition recorded from ipsilateral and contralateral parieto-occipital electrodes (PO7/8; indicated as solid black dots in the topographic maps). Time windows in the ERP plots indicate the windows used to calculate ERP component amplitudes (see text for details). Time windows with a solid outline represent significant differences between cued and uncued ERP components (t tests, p < .05); for peripheral cueing, only the ipsilateral P1 and contralateral Nd components showed a cueing effect. Topographic heat maps associated with each time window/ERP component for targets appearing on the left and right sides are presented, with red indicating most positive activation and blue indicating most negative activation.