Spatial gradients of oculomotor inhibition of return in deaf and normal adults

Research of visual attention networks in deaf individuals: a systematic review

The impact of deafness on visual attention has been widely discussed in previous research. It has been noted that deficiencies and strengths of previous research can be attributed to temporal or spatial aspects of attention, as well as variations in development and clinical characteristics. Visual attention is categorized into three networks: orienting (exogenous and endogenous), alerting (phasic and tonic), and executive control. This study aims to contribute new neuroscientific evidence supporting this hypothesis. This paper presents a systematic review of the international literature from the past 15 years focused on visual attention in the deaf population. The final review included 24 articles. The function of the orienting network is found to be enhanced in deaf adults and children, primarily observed in native signers without cochlear implants, while endogenous orienting is observed only in the context of gaze cues in children, with no differences found in adults. Results regarding alerting and executive function vary depending on clinical characteristics and paradigms used. Implications for future research on visual attention in the deaf population are discussed.

Multisensory integration attenuates visually induced oculomotor inhibition of return

Inhibition of return (IOR) is a mechanism of the attention system involving bias toward novel stimuli and delayed generation of responses to targets at previously attended locations. According to the two-component theory, IOR consists of a perceptual component and an oculomotor component (oculomotor IOR [O-IOR]) depending on whether the eye movement system is activated. Previous studies have shown that multisensory integration weakens IOR when paying attention to both visual and auditory modalities. However, it remains unclear whether the O-IOR effect attenuated by multisensory integration also occurs when the oculomotor system is activated. Here, using two eye movement experiments, we investigated the effect of multisensory integration on O-IOR using the exogenous spatial cueing paradigm. In Experiment 1, we found a greater visual O-IOR effect compared with audiovisual and auditory O-IOR in divided modality attention. The relative multisensory response enhancement (rMRE) and violations of Miller's bound showed a greater magnitude of multisensory integration in the cued location compared with the uncued location. In Experiment 2, the magnitude of the audiovisual O-IOR effect was significantly less than that of the visual O-IOR in single visual modality selective attention. Implications for the effect of multisensory integration on O-IOR were discussed under conditions of oculomotor system activation, shedding new light on the two-component theory of IOR.

Attention capture by brief abrupt-onset cues in deaf individuals

Auditory loss in deaf individuals has been associated with an enhancement in the visual modality. Visual attention is one domain where such plasticity-induced changes have been observed, although which specific attentional mechanisms are improved is still not clear. Using a modified spatial cueing paradigm, we examined attention capture in deaf and normal-hearing participants. Brief abrupt-onset cues were presented for 16 ms either in attended or ignored locations. The to-be-attended locations for each trial were indicated by a horizontal or a vertical bar at the centre of the screen. These were presented either in vertical- or horizontal-only blocks or mixed together. We observed greater negative cueing effects in the NH group compared to deaf. Additionally, people with deafness showed greater capture by cues at ignored locations in the slower responses. These findings shed further light on orienting mechanisms in deaf and help in understanding the specificity of the differences in visual processing between deaf and normal-hearing individuals.

No evidence for an independent retinotopic reference frame for inhibition of return

Inhibition of return (IOR) represents a delay in responding to a previously inspected location and is viewed as a crucial mechanism that sways attention toward novelty in visual search. Although most visual processing occurs in retinotopic, eye-centered, coordinates, IOR must be coded in spatiotopic, environmental, coordinates to successfully serve its role as a foraging facilitator. Early studies supported this suggestion but recent results have shown that both spatiotopic and retinotopic reference frames of IOR may co-exist. The present study tested possible sources for IOR at the retinotopic location including being part of the spatiotopic IOR gradient, part of hemifield inhibition and being an independent source of IOR. We conducted four experiments that alternated the cue-target spatial distance (discrete and contiguous) and the response modality (manual and saccadic). In all experiments, we tested spatiotopic, retinotopic and neutral (neither spatiotopic nor retinotopic) locations. We did find IOR at both the retinotopic and spatiotopic locations but no evidence for an independent source of retinotopic IOR for either of the response modalities. In fact, we observed the spread of IOR across entire validly cued hemifield including at neutral locations. We conclude that these results indicate a strategy to inhibit the whole cued hemifield or suggest a large horizontal gradient around the spatiotopically cued location. PUBLIC SIGNIFICANCE STATEMENT: We perceive the visual world around us as stable despite constant shifts of the retinal image due to saccadic eye movements. In this study, we explore whether Inhibition of return (IOR), a mechanism preventing us from returning to previously attended locations, operates in spatiotopic, world-centered or in retinal, eye-centered coordinates. We tested both saccadic and manual IOR at spatiotopic, retinotopic, and control locations. We did not find an independent retinotopic source of IOR for either of the response modalities. The results suggest that IOR spreads over the whole previously attended visual hemifield or there is a large horizontal spatiotopic gradient. The current results are in line with the idea of IOR being a foraging facilitator in visual search and contribute to our understanding of spatiotopically organized aspects of visual and attentional systems.

Congenital Deafness Leads to Altered Overt Oculomotor Behaviors

The human brain is highly cross-modal, and sensory information may affect a wide range of behaviors. In particular, there is evidence that auditory functions are implicated in oculomotor behaviors. Considering this apparent auditory-oculomotor link, one might wonder how the loss of auditory input from birth might have an influence on these motor behaviors. Eye movement tracking enables to extract several components, including saccades and smooth pursuit. One study suggested that deafness can alter saccades processing. Oculomotor behaviors have not been examined further in the deaf. The main goal of this study was to examine smooth pursuit following deafness. A pursuit task paradigm was used in this experiment. Participants were instructed to move their eyes to follow a target as it moved. The target movements have a possibility of four different trajectories (horizontal, vertical, elliptic clockwise, and elliptic counter-clockwise). Results indicate a significant reduction in the ability to track a target in both elliptical conditions showing that more complex motion processing differs in deaf individuals. The data also revealed significantly more saccades per trial in the vertical, anti-clockwise, and, to a lesser extent, the clockwise elliptic condition. This suggests that auditory deprivation from birth leads to altered overt oculomotor behaviors.

Placeholders dissociate two forms of inhibition of return

Decades of research using Posner's classic spatial cueing paradigm has uncovered at least two forms of inhibition of return (IOR) in the aftermath of an exogenous, peripheral orienting cue. One prominent dissociation concerns the role of covert and overt orienting in generating IOR effects that relate to perception- and action-oriented processes, respectively. Another prominent dissociation concerns the role of covert and overt orienting in generating IOR effects that depend on object- and space-based representation, respectively. Our objective was to evaluate whether these dichotomies are functionally equivalent by manipulating placeholder object presence in the cueing paradigm. By discouraging eye movements throughout, Experiments 1A and 1B validated a perception-oriented form of IOR that depended critically on placeholders. Experiment 2A demonstrated that IOR was robust without placeholders when eye movements went to the cue and back to fixation before the manual response target. In Experiment 2B, we replicated Experiment 2A's procedures except we discouraged eye movements. IOR was observed, albeit only weakly and significantly diminished relative to when eye movements were involved. We conclude that action-oriented IOR is robust against placeholders but that the magnitude of perception-oriented IOR is critically sensitive to placeholder presence when unwanted oculomotor activity can be ruled out.