Abstract
Inhibition of return (IOR) refers to the relative suppression of processing at locations that have recently been attended. It is frequently explored using a spatial cueing paradigm and is characterized by slower responses to cued than to uncued locations. The current study investigates the impact of IOR on overt visual orienting involving saccadic eye movements. Using a spatial cueing paradigm, our experiments have demonstrated that at a cue-target onset asynchrony (CTOA) of 400 ms saccades to the vicinity of cued locations are not only delayed (temporal cost) but also biased away (spatial effect). Both of these effects are basically no longer present at a CTOA of 1200 ms. At a shorter 200 ms CTOA, the spatial effect becomes stronger while the temporal cost is replaced by a temporal benefit. These findings suggest that IOR has a spatial effect that is dissociable from its temporal effect. Simulations using a neural field model of the superior colliculus (SC) revealed that a theory relying on short-term depression (STD) of the input pathway can explain most, but not all, temporal and spatial effects of IOR.
Highlights
To quickly adapt to an ever changing environment, an organism must practice efficient visual orienting
To explore the spatial effect of inhibition of return (IOR), we used a modified cueing task in which the target appeared at the same eccentricity as the cue but its angular distance to the cue was varied between 15u165u
The velocity threshold used to determine whether a saccadic eye movement was made was set to 35u/s, and saccadic response times (SRTs) were computed by subtracting the time at which the eye movement exceeded the velocity threshold from the time at which the target appeared on screen
Summary
To quickly adapt to an ever changing environment, an organism must practice efficient visual orienting. Once an object has been attended, the visual system is subsequently biased against sampling the same spatial location, resulting in less efficient processing of objects appearing there. This bias is labeled inhibition of return (IOR) [2] and has been regarded as a mechanism that encourages orienting towards novelty [3,4,5,6,7]. Responses to targets appearing at the cued location are usually faster than to those appearing at uncued locations This facilitation effect is generally attributed to capture of attention by the onset of the cue [2,3,8]. This hypothesis is echoed by recent theorization of IOR as habituation [10], repetition suppression [11], onset detection cost [12], and short-term depression (STD) of early sensory input [13]
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