Biology subjects

Deubel, H.

Publications and source records attributed to Deubel, H..

11 recordsLinked to original sources

bioRxiv2022

Where we perceive before we look: The distribution of presaccadic attention assessed with dynamic 1/f noise

Already before the onset of a saccadic eye movement, we preferentially process visual information at the upcoming eye fixation. This presaccadic shift of attention is typically assessed via localized test items, which potentially bias the attention measurement. Here we show how presaccadic attention shapes perception from saccade origin to target when no scene-structuring items are presented. Participants made saccades into a 1/f ("pink") noise field, in which we embedded a brief orientation signal at various locations shortly before saccade onset. Local orientation discrimination performance served as a proxy for the allocation of attention. Results demonstrate that (1) saccades are preceded by shifts of attention to their goal location even if they are directed into an unstructured visual field, but the spread of attention, compared to target-directed saccades, is broad; (2) the presaccadic attention shift is accompanied by considerable attentional costs at the presaccadic eye fixation; (3) objects markedly shape the distribution of presaccadic attention - demonstrating the relevance of an item-free approach for measuring attentional dynamics across the visual field.

neuroscience↗

bioRxiv2021

A dynamic pink noise paradigm to assess spatial-temporal attention without biasing perceptual processing

Psychophysical paradigms measure visual attention via localized test items to which observers must react or whose features have to be discriminated. These items, however, potentially interfere with the intended measurement as they bias observers spatial and temporal attention to their location and presentation time. Furthermore, visual sensitivity for conventional test items naturally decreases with retinal eccentricity, which prevents direct comparison of central and peripheral attention assessments. We developed a stimulus that overcomes these limitations. A brief oriented discrimination signal is seamlessly embedded into a continuously changing 1/f noise field, such that observers cannot anticipate potential test locations or times. Using our new protocol, we demonstrate that local orientation discrimination accuracy for 1/f filtered signals is largely independent of retinal eccentricity. Moreover, we show that items present in the visual field indeed shape the distribution of visual attention, suggesting that classical studies investigating the spatiotemporal dynamics of visual attention via localized test items may have obtained a biased measure. We recommend our protocol as an efficient method to evaluate the behavioral and neurophysiological correlates of attentional orienting across space and time. Significance statementWhere (and when) we pay attention can be experimentally quantified via visual sensitivity: Attending to a certain visual signal results in better detection and feature discrimination performance. This approach is widely used, but poses an unrecognized dilemma: The test signal itself, typically a grating or letter stimulus, biases observers perception and expectations - and thus also the attention measurement. We developed a stimulus that manages without test items. The signal to measure attention is seamlessly embedded in a dynamic 1/f noise field, so that neither spatial nor temporal information about signal presentation is conveyed. Unlike with conventional approaches, perception and expectations in this new protocol remain unbiased, and the undistorted spatial and temporal spread of visual attention can be measured.

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bioRxiv2020

Eye and hand movements disrupt attentional control

Voluntary attentional control is the ability to selectively focus on a subset of visual information in the presence of other competing stimuli. While it is well established that this capability is a marker of cognitive control that allows for flexible, goal-driven behavior, it is still an open question how robust it is. In this study we contrasted voluntary attentional control with the most frequent source of automatic, involuntary attentional orienting in daily life--shifts of attention prior to goal-directed eye and hand movements. In a multi-tasking paradigm, we asked participants to attend at a location while planning eye or hand movements elsewhere. We observed that voluntary attentional control suffered with every simultaneous action plan. Crucially, this impairment occurred even when we reduced task difficulty and memory load--factors known to interfere with attentional control. Furthermore, the performance cost was limited to voluntary attention. We observed simultaneous attention benefits at two movement targets without attentional competition between them. This demonstrates that the visual system allows for the concurrent representation of multiple attentional foci. It further reveals that voluntary attentional control is extremely fragile and dominated by automatic, premotor shifts of attention. We propose that action-driven selection disrupts voluntary attention and plays a superordinate role for visual selection.

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bioRxiv2020

Attention capture outside the oculomotor range

Neurophysiological studies demonstrated that attentional orienting is performed by fronto-parietal brain areas which also play an important role in oculomotor control. Accordingly, several studies claimed that exogenous attention can only be allocated to where we can potentially make an eye movement, i.e. within the oculomotor range. We tested this assumption by assessing the disruptive effect of a salient distractor at locations within and beyond participants oculomotor range. Participants rotated their heads ~38{degrees} leftwards to prevent them from performing large rightward saccades. In this posture, participants fixated the screen center and focused their attention on a location on the left side of the screen, where they had to discriminate the orientation of a visual noise patch. While assessing visual orientation sensitivity - an established proxy of visual attention - at this endogenously attended location, we flashed a salient cue either at the attended location or at various locations inside or outside their oculomotor range. We found that whenever the salient cue occurred at a location other than the endogenously attended location, it withdrew visual attention and significantly disrupted endogenous attentional orienting. Crucially, this effect occurred regardless of whether the cue was presented within or beyond participants oculomotor range, demonstrating that exogenous events equally grab our attention both inside and outside the eyes reach. Since spatial exogenous attention was attracted unrestrictedly toward locations to which no saccade could be executed, the coupling of attention and eye movement control is less tight than, for example, the prominent "Premotor Theory of Attention" suggests. Rather, attention can be shifted freely over the entire visual range, independent of pathological and physiological limitations of the eye movement system.

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bioRxiv2020

Theory of Visual Attention (TVA) in Action: Assessing Premotor Attention in Simultaneous Eye-Hand Movements

Attention shifts that precede goal-directed eye and hand movements are regarded as markers of motor target selection. Whether effectors compete for a single, shared attentional resource during simultaneous eye-hand movements or whether attentional resources can be allocated independently towards multiple target locations is controversially debated. Independent, effector-specific target selection mechanisms underlying parallel allocation of visuospatial attention to saccade and reach targets would predict an increase of the overall attention capacity with the number of active effectors. We test this hypothesis in a modified Theory of Visual Attention (TVA; Bundesen, 1990) paradigm. Participants reported briefly presented letters during eye, hand, or combined eye-hand movement preparation to centrally cued locations. Modeling the data according to TVA allowed us to assess both the overall attention capacity and the deployment of visual attention to individual locations in the visual work space. In two experiments, we show that attention is predominantly allocated to the motor targets - without pronounced competition between effectors. The parallel benefits at eye and hand targets, however, have concomitant costs at non-motor locations, and the overall attention capacity does not increase by the simultaneous recruitment of both effector systems. Moreover, premotor shifts of attention dominate over voluntary deployment of processing resources, yielding severe impairments of voluntary attention allocation. We conclude that attention shifts to multiple effector targets without mutual competition given that sufficient processing resources can be withdrawn from movement-irrelevant locations.

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bioRxiv2019

Visual landmarks calibrate auditory space across eye movements

Visual objects that are present both before and after eye movements can act as landmarks, aiding localization of other visual stimuli. We investigated whether visual landmarks would also influence auditory localization - despite participants head position remaining unchanged. Participants made eye-movements from central fixation to a peripheral visual landmark, which either remained stationary or was covertly displaced. Following the movement, participants judged whether a stimulus (auditory or visual) was shifted in location relative to before the movement. Visual localization estimates shifted along with the landmark, although the landmark displacement itself went unnoticed. Interestingly, auditory localization estimates were also displaced. Thus, despite identical auditory input reaching the ears, two auditory stimuli originating from the same position were perceived as spatially distinct when the visual landmark moved. These results are consistent with the idea that auditory spatial information is encoded within an eye-centered reference frame and subject to spatial recalibration by visual landmarks. HighlightsO_LIVisual landmarks affect stimulus localization across eye movements C_LIO_LIWe show this also for auditory stimuli, even when the head remains stable C_LIO_LIDue to a visual landmark displacement, identical auditory stimuli are perceived as shifted C_LIO_LIThis suggests that auditory space is calibrated on eye-centered maps across saccades C_LI

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bioRxiv2019

Sounds are remapped across saccades

To achieve visual space constancy, our brain remaps eye-centered projections of visual objects across saccades. Here, we measured saccade trajectory curvature following the presentation of visual, auditory, and audiovisual distractors in a double-step saccade task to investigate if this stability mechanism also accounts for localized sounds. We found that saccade trajectories systematically curved away from the position at which either a light or a sound was presented, suggesting that both modalities are represented in eye-centered oculomotor centers. Importantly, the same effect was observed when the distractor preceded the execution of the first saccade. These results suggest that oculomotor centers keep track of visual, auditory and audiovisual objects by remapping their eye-centered representations across saccades. Furthermore, they argue for the existence of a supra-modal map which keeps track of multi-sensory object locations across our movements to create an impression of space constancy.

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bioRxiv2019

Stimulus blanking reveals transsaccadic feature transfer

Across saccadic eye movements, the visual system receives two successive static images corresponding to the pre- and the postsaccadic projections of the visual field on the retina. The existence of a mechanism integrating the content of these images is today still a matter of debate. Here, we studied the transfer of a visual feature across saccades using a blanking paradigm. Participants moved their eyes to a peripheral grating and discriminated a change in its orientation occurring during the eye movement. The grating was either constantly on the screen or briefly blanked during and after the saccade. Moreover, it either was of the same luminance as the background (i.e., isoluminant) or anisoluminant with respect to it. We found that for anisoluminant grating, the orientation discrimination across saccade was improved when a blank followed the onset of the eye movement. Such effect was however abolished with isoluminant grating. Additionally, performance was also improved when an anisoluminant grating presented before the saccade was followed by an isoluminant one. These results demonstrate that a detailed representation of the presaccadic image was transferred across saccades allowing participants to perform better on the trans-saccadic orientation task. While such a transfer of visual orientation across saccade is masked in real-life anisoluminant conditions, the use of a blank and of isoluminant postsaccadic grating allowed here to reveal its existence.\n\nSignificance statementStatic objects are perceived as not moving across eye movements despite their visual projection shifts on our retina. To compensate for such shifts and create a continuous perception of space, our brain may keep track of objects visual features across our movements. We found that shortly blanking a contrast-defined object during and after saccades allows to recover a detailed representation of its orientation. We propose that the transfer of visual content across saccades revealed with the use of a simple blank plays an important role in ensuring our continuous and stable perception of the world.

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bioRxiv2018

Pre-saccadic remapping relies on dynamics of spatial attention

Each eye movement shifts the projections of the visual scene on the retina. It has been proposed that the receptive fields of neurons in oculomotor areas are remapped pre-saccadically to account for these shifts. While remapping of the whole visual scene seems prohibitively complex, selection by visual attention may limit these processes to a subset of attended locations. Because attentional selection consumes time, remapping of attended locations should evolve in time, too. In our study, we cued a spatial location by presenting an attention capturing cue at different times before a saccade and constructed detailed maps of attentional allocation across the visual field. We observed no remapping when the cue appeared shortly before saccade. In contrast, when the cue appeared sufficiently early before saccade, attentional resources were reallocated to the remapped location. Our results suggest that pre-saccadic remapping is an attentional process relying on the spatial and temporal dynamics of visual attention.

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bioRxiv2017

Visual attention is not always spatially coupled to subsequent oculomotor program

The premotor theory of attention postulates that spatial attention arises from the activation of saccade areas and that the deployment of attention is the consequence of motor programming. Yet, attentional and oculomotor processes have been shown to be dissociable at the neuronal level in covert attention tasks. To investigate a potential dissociation at the behavioral level, we instructed human participants to saccade towards one of two nearby, competing saccade cues. The spatial distribution of visual attention was determined using oriented Gabor stimuli presented either at the cue locations, between them or at several other equidistant locations. Results demonstrate that accurate saccades towards one of the cues were associated with presaccadic enhancement of visual sensitivity at the respective saccade endpoint compared to the non-saccaded cue location. In contrast, averaging saccades, landing between the two cues, were not associated with attentional facilitation at the saccade endpoint, ruling out an obligatory coupling of attentional deployment to the oculomotor program. Rather, attention before averaging saccades was equally distributed to the two cued locations. Taken together, our results reveal a spatial dissociation of visual attention and saccade programming. They suggest that the oculomotor program depends on the state of attentional selection before saccade onset, and that saccade averaging arises from unresolved attentional selection.

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bioRxiv2017

Spreading pre-saccadic attentional resources without trade-off

When preparing a saccade, attentional resources are focused at the saccade target and its immediate vicinity. Here we show that this does not hold true when saccades are prepared towards a recently extinguished target. We obtained detailed maps of orientation sensitivity when participants prepared a saccade toward a target that either remained on the screen or disappeared before the eyes moved. We found that attention was mainly focused at the immediate surround of the visible target and increasingly spread to more peripheral locations as a function of the delay between the targets disappearance and the saccade. Interestingly, this spread was accompanied by an overall increase in sensitivity, speaking against a dilution of limited resources over a larger spatial area. We hypothesize that these results reflect the behavioral consequences of the spatio-temporal dynamics of visual receptive fields in the presence and in the absence a structured visual cue.

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