Exogenous orienting of attention typically produces an early facilitatory effect and a later inhibitory effect, i.e., inhibition of return (IOR). IOR occurs not only in spatial but also in non-spatial domains. Although neural mechanisms associated with spatial IOR have been well established, neural correlates underlying non-spatial IOR remain to be elucidated. In this fMRI study, we compared neural correlates of spatial and non-spatial IOR by adopting a 2 (cue type: location vs. color)x2 (stimulus onset asynchrony, SOA: long vs. short)x2 (cue validity: cued vs. uncued) factorial design. Behaviorally, spatial cueing induced the typical biphasic (i.e., the early facilitatory and later inhibitory) effects, while color cueing induced inhibitory effects at both short and long SOAs. Neurally, we found both shared and specific neural correlates of spatial and non-spatial IOR. As compared with short SOA (cued and uncued trials combined), spatial and color cueing at long SOA conjointly activated bilateral precentral gyrus and bilateral lateral occipital cortex, while spatial cueing, but not color cueing, specifically activated bilateral superior parietal cortex. Moreover, left middle frontal gyrus and left inferior frontal gyrus showed significantly higher neural activity in cued trials than in uncued trials during color-based IOR, but not during location-based IOR, implying that episodic retrieval process in the prefrontal cortex may be involved to inhibit old object representations during non-spatial IOR [Grison, S., Paul, M. A., Kessler, K., & Tipper, S. P. (2005). Inhibition of object identity in inhibition of return: Implications for encoding and retrieving inhibitory processes. Psychonomic Bulletin & Review, 12, 553-558; Tipper, S. P., Grison, S., & Kessler, K. (2003). Long-term inhibition of return of attention. Psychological Science, 14, 19-25]. Theoretical implications of the shared and differential neural activity associated with spatial and non-spatial IOR are discussed.

Inhibition of return (IOR) is a phenomenon that has been thought to be closely associated with attention mechanisms. In particular, it might arise from the operation of an attentional mechanism that facilitates visual search by inhibiting both covert attention and eye movements from returning to recently inspected locations. Although IOR has received a great deal of research interest, and mechanisms involving sensory, perceptual, and motor consequences have been proposed, no consensus has yet been reached regarding the stages of information processing at which IOR operates. In the present study, we utilized event-related potential (ERP) measures of visual and motor processes to investigate the processing changes underlying IOR. In three experiments, involving localization, detection, or Go-NoGo discrimination, participants were required to make manual responses to target stimuli. In each of these experiments, IOR was associated with a slowing of premotor processes as indicated by a modulation of the onset of

The authors examined the effects of d-amphetamine on the ability to perform a cued target-detection task that measured inhibition of return (IOR). IOR is a reflexive inhibitory mechanism that delays attention from returning to a previously attended location and has been shown to increase the efficiency of a visual search. Adults (N=14) with a history of cocaine use performed the task under 4 doses of d-amphetamine (0, 10, 20, and 30 mg). The results showed active d-amphetamine doses increased the duration of IOR. By increasing the delay in returning attention to a previously attended location, d-amphetamine might reduce time spent searching previously attended locations, increasing the efficiency of visual searches. ((c) 2005 APA, all rights reserved).

Inhibition of return (IOR), first described in 1984, was considered to be a general phenomenon for ensuring that attention would be allocated to successive stimuli in the environment. In the present research, IOR was expressed in forced-choice identification tasks with either reaction time or accuracy as the dependent measure. Thus, the generality of IOR was supported, because response inhibition cannot explain IOR found with accuracy measures. Concepts from the variable and permeable filters metaphor are used to suggest how changes in attention can change expression of IOR by rapid variation in perceptual threshold.