Sensory and motor mechanisms of oculomotor inhibition of return

Human electrophysiological (EEG) studies also showed that target-elicited early visual ERP components (P1 and N1) are reduced for cued targets (see Prime and Ward 2006, for a review). Reduced BOLD signal to cued targets has also been observed in human visual cortex (e.g., Anderson and Rees 2011).

One could always use two differential equations to approximate this input reduction, but we chose to use the alpha function for simplicity.

One might suggest that this mechanism should not be regarded as a contributor to IOR because the forward facilitation it generates (saccade momentum) causes a disadvantage for return saccades. Although such a suggestion has merit, so too does our maintenance of the IOR terminology. Our previous modeling papers (Satel et al. 2011; Wang et al. 2011) have addressed two extreme situations where the behavioral effects had been, by convention in the field, labeled as IOR: (1) covert orienting where IOR is elicited by uninformative peripheral cues while the participant maintains fixation until target presentation; (2) overt orienting where IOR is used to label longer latencies for saccades returning to previously fixated locations (e.g., Klein and MacInnes 1999). We prefer to continue to use “IOR” to label both cases because we are following the “convention” in the field where IOR is used to loosely refer to a set of processes that facilitate orienting to novelty. The importance of our contribution rests not on terminology but on the computationally explicit nature of the sensory and motor mechanisms we have proposed to implement these processes.

Readers may be surprised that the saccade back to the central fixation was no slower than the one to the peripheral box (in response to the cue) in the M task. It should be noted that unlike saccades to the targets of which the direction was unpredictable, saccades made in response to the cue-back signal were always directed to the central box.

Although the conceptual underpinning seems quite different (rooted as it is in the notion of cue-target integration) Lupianez’s proposal of a cue-induced “onset detection cost” (Lupiáñez 2010; see also Hu et al. 2011) shares quite a few properties with this suppression effect that is fundamental to our sensory mechanism.