The Mechanisms Of Location-Based Inhibition Of Return In Three-Dimensional Space

We live in a real three-dimensional (3D) environment, in which there is the depth dimension. Therefore, to survive in a competitive environment, we have to voluntarily select objects according to current goals through mechanisms of selective attention while dealing with sudden events that are not directly related to our original intention. Therefore, the abilities of visuospatial processing and attentional orienting/reorienting in 3D space were closely related to our live, were interaction with the environment we live, meanwhile, also were a basic cognitive abilities. Therefore, to understand the mechanisms of visuospatial processing and location-based inhibition of return in three-dimensional space were important and prominent. The present study using 12 experiments in neurological and behavioral methods to investigate them.Constructing a virtual 3D environment and presenting the target either closer to or farther from the participants in an adapted version of the Posner spatial-cuing paradigm in study 1, we aimed to investigate the location-based inhibition of return (IOR) along depth plane in 3D space. Based on the Theeuwes’s study, we operated the different trajectories that attention orient/reoriented, results showed that attention could be oriented/reoriented effectively along depth plane in 3D space to induce the location-based IOR, and the IOR were found either in central view or in peripheral view. Thus, we suggested that the IOR is not entirely "depth-blind"Based on the results of study 1, study 2 operated the different trajectories that attention orient/reoriented in 3D space, aiming to investigate whether the IOR effect is the same or different along different trajectories in 3D space. The results showed that there were asymmetrical IOR effects when attention oriented/reoriented along the uncued depth within the same hemispace. That is the IOR effects were depth specific when targets appeared in the near-depth plane, while was not depth specific when targets appeared in the far depth plane. Apart from the above results, we also found that attention oriented/reoriented along the same depth yet different hemispaces experienced a reduction in the size of IOR in comparison to the other two conditions, thus indicating that the direction-specific mechanisms of attentional orienting/reorienting were different. Taken together, we suggested that the ecological importance of the 3D world influences the direction of attentional shift on IOR in 3D space. In addition, we conducted a repeated experiment that included a neutral cue condition (using double cues) in order to reveal the extent to which that discrepant effect is due to inhibition at the cue versus response-slowing in the uncued location. The results suggested that there was no more significant an IOR effect produced by slowing down RTs to targets at uncued locations, than by speeding up RTs to targets at cued locations.According to the IOR effects were different in near and far spaces, study 3 investigated whether the different mechanisms of visuospatial processing in near and far spaces would influence the effects. By using the fMRI technology and controlling the sizes of stimuli in far and near spaces, asking the participants to make a manual response in far and near spaces, respectively. We mainly focused on the main effect of spatial domain (far space vs. near space), thus, the sizes of stimuli in far and near spaces were modeled separately. In each condition, the GLM was used to construct a multiple regression design matrix that included two conditions:"Near> Far". The results showed that in retinotopic matched condition (Match condition), an extended activation cluster, including bilateral superior occipital gyrus (SOG) and the Parieto-occipital junction (POJ), showed significantly higher neural activity in near space processing than in far space processing. We also identified brain regions that were associated with differential processing of Spatial Domains in the perceptual matched condition (Natural condition). The results showed an extended activation cluster, including the right lingual gyrus, the left calcarine sulcus, bilateral SOG, and the POJ, showed significantly higher neural activity in near space processing than in far space processing. For the reverse contrast, bilateral inferior occipital gyrus (IOG) was activated. Then, we isolated the brain regions that showed near space preference independent of object size. A conjunction analysis between the main effect of spatial domain ("Near> Far") in the natural and match conditions were performed. We found that the POJ and bilateral SOG were activated in the conjunction analysis. Then, we continued to investigat the neural interface between dorsal and the ventral streams when the participants were asked to make a manual response in the 3D space. We used the contrast "Near> Far" as the psychological factor and used the neural activity in the POJ and bilateral SOG as the physiological factors, respectively to make a connectivity with the whole brain. The results showed that the POJ showed increased neural coupling with both the dorsal and ventral visual streams for far space processing than near space processing. The match and natural conditionss revealed consistent results. These results demonstrated that POJ acted as a neural interface between the dorsal and ventral streams.In conclusion, the present study demonstrated that (1) Attention could be oriented/reoriented effectively along depth plane in 3D space to induce location based inhibition of return, which was not "depth blindness"; (2) The ecological importance of the 3D world, that is the different spatial processing between near and far spaces could influence the directions of attentional shift on IOR in 3D space; (3) In addition to its role in near space processing, the POJ showed enhanced functional connectivity with both the dorsal and ventral streams during far space processing irrespective of the target size, which directly supported the role of the POJ acted as a neural interface between the dorsal and ventral streams. In the future, basing on the neurological mechanisms of visuospatial processing in three-dimensional, we will use the ERPs and the fMRI technologies to investigate the neurological mechanisms of location-based IOR in 3D space, and use the tDAS and the patients with brain injury to investigate the neurological mechanisms of location-based IOR in 3D space.