Neural correlates of spatial and non-spatial inhibition of return (IOR) in attentional orienting

Levels of neuroticism can predict attentional performance during cross-modal nonspatial repetition inhibition

Inhibition of return (IOR) refers to the slower response to targets presented at previously attended locations, and such repetition-induced inhibition has been found to be differentially associated with personality traits. Although it has been well documented how personality traits affect spatial IOR, a mechanism associated with the attentional orienting network, there is not yet a consensus as to the relationship between personality traits and nonspatial repetition inhibition, a mechanism associated with the attentional executive network. The present study herein examined how the Big Five personality traits relate to cross-modal nonspatial repetition inhibition. Participants completed the NEO-PI-R and performed a cross-modal nonspatial repetition inhibition task built on the prime-neutral cue-target paradigm, in which the relationships of the identities and modalities between the prime and the target were manipulated. The results showed a significant nonspatial inhibitory effect and the effect was larger under the visual-auditory condition than under the auditory-visual condition. More importantly, neuroticism was associated with decreased cross-modal nonspatial inhibitory effect, presumably due to impaired attentional control. However, such a result was only found in the visual-auditory condition. We propose that retrieving previous prime representations under the visual-auditory condition requires a large consumption of cognitive resources, making inhibitory control more difficult for individuals with high neuroticism. These findings provide new insight into the influence of personality traits on attentional performance requiring nonspatial inhibitory control and enrich the relationship between neuroticism and repetition-induced inhibition.

Aging and Inhibition of Return to Locations and Objects

Inhibition of return (IOR) is thought to reflect a cognitive mechanism that biases attention from returning to previously engaged items. While models of cognitive aging have proposed deficits within select inhibitory domains, older adults have demonstrated preserved IOR functioning in previous studies. The present study investigated whether inhibition associated with objects shows the same age patterns as inhibition associated with locations. Young adults (18-22 years) and older adults (60-86 years) were tested in two experiments measuring location- and object-based IOR. Using a dynamic paradigm (Experiment 1), both age groups produced significant location-based IOR, but only young adults produced significant object-based IOR, consistent with previous findings. However, with a static paradigm (Experiment 2), young adults and older adults produced both location- and object-based IOR, indicating that object-based IOR is preserved in older adults under some conditions. The findings provide partial support for unique age-related inhibitory patterns associated with attention to objects and locations.

Ketamine-Induced Alteration of Working Memory Utility during Oculomotor Foraging Task in Monkeys

Impairments of working memory (WM) are commonly observed in a variety of neurodegenerative disorders but they are difficult to quantitatively assess in clinical cases. Recent studies in experimental animals have used low-dose ketamine (an NMDA receptor antagonist) to disrupt WM, partly mimicking the pathophysiology of schizophrenia. Here, we developed a novel behavioral paradigm to assess multiple components of WM and applied it to monkeys with and without ketamine administration. In an oculomotor foraging task, the animals were presented with 15 identical objects on the screen. One of the objects was associated with a liquid reward, and monkeys were trained to search for the target by generating sequential saccades under a time constraint. We assumed that the occurrence of recursive movements to the same object might reflect WM dysfunction. We constructed a "foraging model" that incorporated (1) memory capacity, (2) memory decay, and (3) utility rate; this model was able to explain more than 92% of the variations in behavioral data obtained from three monkeys. Following systemic administration of low dosages of ketamine, the memory capacity and utility rate were dramatically reduced by 15% and 57%, respectively, while memory decay remained largely unchanged. These results suggested that the behavioral deficits during the blockade of NMDA receptors were mostly due to the decreased usage of short-term memory. Our oculomotor paradigm and foraging model appear to be useful for quantifying multiple components of WM and could be applicable to clinical cases in future studies.

Crossmodal Nonspatial Repetition Inhibition Due to Modality Shift

Previous studies have found that processing of a second stimulus is slower when the modality of the first stimulus differs, which is termed the modality shift effect. Moreover, people tend to respond more slowly to the second stimulus when the two stimuli are similar in the semantic dimension, which is termed the nonspatial repetition inhibition effect. This study aimed to explore the modality shift effect on nonspatial repetition inhibition and whether such modulation was influenced by different temporal intervals. A cue-target paradigm was adopted in which modality priming and identity priming were manipulated at three interstimuli intervals. The results showed that the response times under the modality shift condition were slower than those under the modality repeat condition. In trials with modality shift, responses to congruent cues and targets were slower than to incongruent cue-target combinations, indicating crossmodal nonspatial repetition inhibition. The crossmodal nonspatial repetition inhibition effect decreased with increasing interstimuli interval. These results provide evidence that the additional intervening event proposed in previous studies is not necessary for the occurrence of crossmodal nonspatial repetition inhibition.

Bimodal-divided attention attenuates visually induced inhibition of return with audiovisual targets

Inhibition of return (IOR) refers to the slower response to a target appearing at a previously attended location in a cue-target paradigm. It has been greatly explored in the visual or auditory modality. This study investigates differences between the IOR of audiovisual targets and the IOR of visual targets under conditions of modality-specific selective attention (Experiment 1) and divided-modalities attention (Experiment 2). We employed an exogenous spatial cueing paradigm and manipulated the modalities of targets, including visual, auditory, or audiovisual modalities. The participants were asked to detect targets in visual modality or both visual and auditory modalities, which were presented on the same (cued) or opposite (uncued) side as the preceding visual peripheral cues. In Experiment 1, we found the comparable IOR with visual and audiovisual targets when participants were asked to selectively focus on visual modality. In Experiment 2, however, there was a smaller magnitude of IOR with audiovisual targets as compared with visual targets when paying attention to both visual and auditory modalities. We also observed a reduced multisensory response enhancement effect and race model inequality violation at cued locations relative to uncued locations. These results provide the first evidence of the IOR with audiovisual targets. Furthermore, IOR with audiovisual targets decreases when paying attention to both modalities. The interaction between exogenous spatial attention and audiovisual integration is discussed.

The Different Inhibition of Return (IOR) Effects of Emergency Managerial Experts and Novices: An Event-Related Potentials Study

Inhibition of return (IOR) is an important effect of attention. However, the IOR of emergency managerial experts is unknown. By employing emergency and natural scene pictures in expert-novice paradigm, the present study explored the neural activity underlying the IOR effects for emergency managerial experts and novices. In behavioral results, there were no differences of IOR effects between novices and emergency managerial experts, while the event-related potentials (ERPs) results were different between novices and experts. In Experiment 1 (novice group), ERPs results showed no any IOR was robust at both stimulus-onset asynchrony (SOA) of 200 ms and 400 ms. In Experiment 2 (expert group), ERPs results showed an enhanced N2 at SOA of 200 ms and attenuated P3 at cued location in the right parietal lobe and adjacent brain regions than uncued location at SOA of 200 ms. The findings of the two experiments showed that, relative to the novices, IOR for the emergency managerial experts was robust, and dominated in the right parietal lobe and adjacent brain regions, suggesting more flexible attentional processing and higher visual search efficiency of the emergency managerial experts. The findings indicate that the P3, possible N2, over the right parietal lobe and adjacent brain regions are the biological indicators for IOR elicited by post-cued emergency pictures for emergency managerial experts.

Neural correlates of the preserved inhibition of return in schizophrenia

Inhibition of return (IOR) is an attentional mechanism that previously has been reported to be either intact or blunted in subjects with schizophrenia (SCZ). In the present study, we explored the neural mechanism of IOR in SCZ by comparing the target-locked N1 and P1 activity evoked by valid-cued trials with that evoked by invalid-cued trials. Twenty-seven schizophrenia patients and nineteen healthy controls participated in a task involving covert orienting of attention with two stimulus onset asynchronies (SOAs: 700 ms and 1200 ms) during which 64-channel EEG data were recorded. Behavioral reaction times (RTs) were longer in response to valid-cued trials than to invalid-cued ones, suggesting an intact IOR in SCZ. However, reduced N1 amplitude elicited by valid-cued trials suggested a stronger inhibition of attention from being oriented to a previously cued location, and therefore a relative inhibition of perceptual processing at that location in SCZ. These results indicate that altered N1 activity is associated with the preservation of IOR in SCZ and could be a sensitive marker to track the IOR effect.

Dissociable identity- and modality-specific neural representations as revealed by cross-modal nonspatial inhibition of return

There are ongoing debates on whether object concepts are coded as supramodal identity-based or modality-specific representations in the human brain. In this fMRI study, we adopted a cross-modal "prime-neutral cue-target" semantic priming paradigm, in which the prime-target relationship was manipulated along both the identity and the modality dimensions. The prime and the target could refer to either the same or different semantic identities, and could be delivered via either the same or different sensory modalities. By calculating the main effects and interactions of this 2 (identity cue validity: "Identity_Cued" vs. "Identity_Uncued") × 2 (modality cue validity: "Modality_Cued" vs. "Modality_Uncued") factorial design, we aimed at dissociating three neural networks involved in creating novel identity-specific representations independent of sensory modality, in creating modality-specific representations independent of semantic identity, and in evaluating changes of an object along both the identity and the modality dimensions, respectively. Our results suggested that bilateral lateral occipital cortex was involved in creating a new supramodal semantic representation irrespective of the input modality, left dorsal premotor cortex, and left intraparietal sulcus were involved in creating a new modality-specific representation irrespective of its semantic identity, and bilateral superior temporal sulcus was involved in creating a representation when the identity and modality properties were both cued or both uncued. In addition, right inferior frontal gyrus showed enhanced neural activity only when both the identity and the modality of the target were new, indicating its functional role in novelty detection.

Behavioral and neural interaction between spatial inhibition of return and the Simon effect

It has been well documented that the anatomically independent attention networks in the human brain interact functionally to achieve goal-directed behaviors. By combining spatial inhibition of return (IOR) which implicates the orienting network with some executive function tasks (e.g., the Stroop and the flanker tasks) which implicate the executive network, researchers consistently found that the interference effects are significantly reduced at cued compared to uncued locations, indicating the functional interaction between the two attention networks. However, a unique, but consistent effect is observed when spatial IOR is combined with the Simon effect: the Simon effect is significantly larger at the cued than uncued locations. To investigate the neural substrates underlying this phenomenon, we orthogonally combined the spatial IOR with the Simon effect in the present event-related fMRI study. Our behavioral data replicated previous results by showing larger Simon effect at the cued location. At the neural level, we found shared spatial representation system between spatial IOR and the Simon effect in bilateral posterior parietal cortex (PPC); spatial IOR specifically activated bilateral superior parietal cortex while the Simon effect specifically activated bilateral middle frontal cortex. Moreover, left precentral gyrus was involved in the neural interaction between spatial IOR and the Simon effect by showing significantly higher neural activity in the "Cued_Congruent" condition. Taken together, our results suggest that due to the shared spatial representation system in the PPC, responses were significantly facilitated when spatial IOR and the Simon effect relied on the same spatial representations, i.e., in the "Cued_Congruent" condition. Correspondingly, the sensorimotor system was significantly involved in the "Cued_Congruent" condition to fasten the responses, which indirectly resulted in the enhanced Simon effect at the cued location.

Visual spatial cognition in neurodegenerative disease

Visual spatial impairment is often an early symptom of neurodegenerative disease; however, this multi-faceted domain of cognition is not well-assessed by most typical dementia evaluations. Neurodegenerative diseases cause circumscribed atrophy in distinct neural networks, and accordingly, they impact visual spatial cognition in different and characteristic ways. Anatomically-focused visual spatial assessment can assist the clinician in making an early and accurate diagnosis. This article will review the literature on visual spatial cognition in neurodegenerative disease clinical syndromes, and where research is available, by neuropathologic diagnoses. Visual spatial cognition will be organized primarily according to the following schemes: bottom-up/top-down processing, dorsal/ventral stream processing, and egocentric/allocentric frames of reference.

Deficient inhibition of return in chronic but not first-episode patients with schizophrenia

BACKGROUND

Inhibition of return (IOR) has been tested in patients with schizophrenia with contradictory results. Some studies indicated that patients with schizophrenia have normal levels of IOR; however, other studies reported delayed or blunted IOR. Inconsistency in findings might be due to differences across studies in relevant aspects associated with disease, such as heterogeneity of the disorder, different medications, onset and severity of the illness. The present study was to explore different patterns of IOR in antipsychotic medication free first-episode schizophrenia and chronic schizophrenia.

METHODS

Forty two patients with first-episode schizophrenia, 44 patients with chronic schizophrenia, and 38 healthy controls were included in the study. All subjects went through a covert orienting of attention task with seven stimulus onset asynchrony (SOA) intervals (400 ms, 500 ms, 600 ms, 700 ms, 800 ms, 1200 ms and 1500 ms).

RESULTS

Compared with healthy controls, the magnitude and onset of IOR in first-episode patients with schizophrenia were intact. However, in patients with chronic schizophrenia, there was an attenuated cuing effect especially at SOA 700 ms; in addition, there was a robust IOR until at SOAs 800 ms or above. Moreover, the illness duration and the number of psychotic episodes were significantly correlated with the validity effect at SOAs 400 ms and 600 ms.

CONCLUSION

Our study suggests that deficient IOR presents in chronic but not in first-episode patients with schizophrenia. IOR deficit in schizophrenia may begin during the course of illness and deteriorate over the course of illness. Our findings are consistent with the neurodegenerative model of schizophrenia.

Biasing the organism for novelty: A pervasive property of the attention system

Although the functional and anatomical independences between the orienting and the executive attention networks have been well established, surprisingly little is known about the potential neural interaction between them. Recent studies point out that spatial inhibition of return (IOR), a mechanism associated with the orienting network, and nonspatial inhibition of return, a mechanism associated with the executive network, might bias the organism for novel locations and objects, respectively. By orthogonally combining the spatial and the nonspatial IOR paradigms in this fMRI study, we demonstrate that the orienting and the executive networks interact and compensate each other in biasing the attention system for novelty. Behaviorally, participants responded slower to the target at the old location only when the color of the target was novel, and participants responded slower to the old color representation only when the target appeared at a novel spatial location. Neurally, the orienting network was involved in slowing down responses to the old location only when the nonspatial IOR mechanism in the executive network was not operative (i.e., when the color of the target was novel); the prefrontal executive network was involved in slowing down responses to the old color representation only when the spatial IOR mechanism in the orienting network was not functioning (i.e., when the target appeared at a novel location).

Space-based but not object-based inhibition of return is impaired in Parkinson's disease

Impairments in certain aspects of attention have frequently been reported in Parkinson's disease (PD), including reduced inhibition of return (IOR). Recent evidence suggests that IOR can occur when attention is directed at objects or locations, but previous investigations of IOR in PD have not systematically compared these two frames of reference. The present study compared the performance of 18 nondemented patients with PD and 18 normal controls on an IOR task with two conditions. In the "object-present" condition, objects surrounded the cues and targets so that attention was cued to both a spatial location and to a specific object. In the "object-absent" condition, surrounding objects were not presented so that attention was cued only to a spatial location. When participants had to rely on space-based cues, PD patients demonstrated reduced IOR compared to controls. In contrast, when objects were present in the display and participants could use object-based cues, PD patients exhibited normal IOR. These results suggest that PD patients are impaired in inhibitory aspects of space-based attention, but are able to overcome this impairment when their attention can be directed at object-based frames of reference. This dissociation supports the view that space-based and object-based components of attention involve distinct neurocognitive processes.