Biology subjects

Goettker, A.

Publications and source records attributed to Goettker, A..

10 recordsLinked to original sources

bioRxiv2026

Blinks are strategically coupled with head movements in unconstrained natural gaze behavior

Blinks are a ubiquitous yet largely unnoticed aspect of human vision, despite causing frequent interruptions of visual input that can amount to up to 10% of waking time. By leveraging a large dataset of unconstrained gaze behavior during two natural tasks, we found a novel behavioral strategy to limit the impact of blinks: blinks were strategically coupled with head movements, which minimizes information loss due to unreliable visual input during head movements. Specifically, blink probability increased with higher head velocities and showed strong temporal modulation relative to head movement onset: Blink probability was reduced before head movement initiation and then peaked during the head movement. The strength of this coupling was tailored to the individual needs of participants, with participants with higher baseline blink showing a stronger synchronization. This indicates that blinks are a part of an individually coordinated strategy when orchestrating eye and head movements during unconstrained natural behavior.

neuroscience↗

bioRxiv2026

Eye movements reveal the intuitive understanding of materials and their behavior

Does a metal ball sink or float when dropped into water? Answering this intuitively simple question relies on our understanding of materials and their physics1. Knowing materials helps us to recognize objects, estimate their properties, and predict how they will behave when interacting with other objects or materials2,3. This leads to expectations about material behaviors already in young infants4,5, for example, that a metal ball should sink in water. Typically, properties and affordances of materials have been studied with perceptual tasks. But even though explicit perceptual judgments allow us to identify important determinants of material understanding, it is not clear how they relate to dynamic predictions of material behavior -- which we need for successful interactions with objects3. Here, we tap into material understanding by leveraging anticipatory eye movements, which have been shown to be direct readouts of trajectory predictions6 and can also reflect expectations about material properties such as elasticity or mass7. This allows us to reveal the temporal evolution of dynamic predictions based on material properties. Furthermore, by using novel stimuli that violate intuitive expectations about material behavior, we demonstrate that even though dynamic predictions can be learned over time, there remains a fundamental difference between predictions in line with and against our intuitive expectations.

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bioRxiv2025

Chromatic and Achromatic Contrast Sensitivity in the far Periphery

The contrast sensitivity function (CSF) has been studied extensively since the 1960s, however most studies to date have focused on the central region of the visual field. The current study aims to address two gaps in previous measurements: First, it provides a detailed measurement of the CSF for achromatic and, importantly, also chromatic stimuli in the far periphery of up to 90 degrees of visual angle. Second, we describe visual sensitivity around the monocular/binocular boundary that is naturally present in the far periphery. In the first experiment, the CSF was measured in 3 different conditions: Stimuli were either Achromatic (L+M), Red-Green (L-M) or and Yellow-Violet (S-(L+M)) gabor patches. Overall, results followed the expected patterns established in the near periphery, but achromatic sensitivity in the far periphery was mostly under-estimated by current models of visual perception, the quick decay in sensitivity observed for red-green stimuli slows down in the periphery. The decay of sensitivity for yellow-violett stimuli roughly matches the decay for achromatic stimuli even up to the far periphery. For the second experiment, we compared binocular and monocular visual sensitivity at different locations in the visual field. We observed a consistent increase of visual sensitivity for binocular viewing in the central part of the visual field compared to monocular viewing, but this benefit already decreased within the binocular visual field in the periphery. Together, these data provide a detailed description of visual sensitivity in the far periphery. These measurements can help to improve current models of visual sensitivity and can be vital for applications in full-field visual displays in virtual and augmented reality.

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bioRxiv2024

Keeping Your Eye, Head, and Hand on the Ball: Rapidly Orchestrated Visuomotor Behavior in a Continuous Action Task

In everyday life, we must adapt our behavior to a continuous stream of tasks and time motor responses and periods of resting accordingly. To mimic these challenges, we used a continuous interception computer game (Pong) on an iPad. This allowed us to measure the coordination of eye, hand, and head movements during natural sequential behavior while maintaining the benefits of experimental control. Participants intercepted a moving ball by sliding a paddle at the bottom of the screen so that the ball bounced back and moved toward the computerized opponent. We tested i) how participants adapted their eye, hand, and head movements to this dynamic, continuous task, ii) whether these adaptations are related to interception performance, and iii) how their behavior changed under different conditions and iv) over time. We showed that all movements are carefully adapted to the upcoming action. Pursuit eye movements provide crucial motion information and are emphasized shortly before participants must act; a strategy associated with better performance. Participants also increasingly used pursuit eye movements under more difficult conditions (fast targets and small paddles). Saccades, blinks, and head movements, which would lead to information loss, are minimized at critical times of interception. These strategic patterns are intuitively established and maintained over time and across manipulations. We conclude that humans carefully orchestrate their full repertoire of movements to aid performance and finely adjust them to the changing demands of our environment.

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bioRxiv2024

Spatial and directional tuning of serial dependence for tracking eye movements

An attractive influence of past sensory experience on current behaviour has been observed in many domains, such as for perceptual decisions and motor responses. However, it is unclear what sort of information is integrated across trials, and the limits of this integration, especially for oculomotor behavior. Here we provide a detailed and systematic investigation of the spatial and directional tuning of serial dependence for oculomotor tracking. In a series of experiments, we measured oculomotor responses to sequences of movements: the first movement (the prior) could move at different velocities (5 or 15 deg/s), and could additionally vary in its spatial location or direction relative to the following movement. The second movement (the probe) always moved at the same velocity (10 deg/s) and was constant across all experiments. We observed that eye velocity for the probe movement was faster when following the fast prior compared to following the slow prior, replicating attractive serial dependence. Importantly, this effect stayed consistent for distances of up to 30 deg between probe and prior, strongly suggesting a retinotopic coordinate frame. When we manipulated the direction of the prior, we observed that the strength of the serial dependence on eye velocity as well as eye direction was modulated by the relative angle between prior and probe. We observed stronger serial dependence for prior directions more similar to the probe direction. The strength of the effect on eye velocity and eye direction was correlated, suggesting a shared mechanism controlling these effects. Across all experiments, we observed that even when the prior moved in the opposite direction to the probe, there was a residual attractive effect. This suggests that serial dependence for oculomotor tracking consists of two components, one retinotopic, direction-tuned component and one more general component that is not direction-specific.

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bioRxiv2024

Individual differences reveal similarities in serial dependencies across perceptual tasks, but no relation to serial dependencies for oculomotor behavior

Serial dependence effects from one trial to the next have been observed across a wide range of perceptual tasks, as well as for oculomotor behavior. This opens up the question of whether the effects observed across all of these studies share underlying mechanisms. Here we measured the same group of observers across four different tasks, two perceptual (color judgments and orientation judgments) and two oculomotor (tracking of moving targets and the pupil light reflex). On the group level, we observed significant attractive serial dependence effects for all tasks, except the pupil response. The rare absence of a serial dependence effect for the reflex like pupil light response suggests that sequential effects require cortical processing or even higher-level cognition. In the following step, we leveraged reliable individual differences between observers in the other tasks to test whether there is a trait-like behavior of some observers showing stronger serial dependence effects across all of these tasks. We observed a significant relationship in the strength of serial dependence for the two perceptual experiments, but no relation between the perceptual tasks and oculomotor behavior. This indicates, differences in processing between perception and oculomotor control and the absence of a general trait-like behavior that affects all tasks similarly. However, the shared variance in the strength of serial dependence effects across different perceptual tasks indicates the importance of a similar positive decision bias present, that is reliably different between observers and consistent across different serial dependence tasks.

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bioRxiv2023

Oculomotor routines for perceptual judgments

In everyday life we frequently make simple visual judgments about object properties, e.g., how big or wide is a certain object? Our goal is to test whether there are also task specific oculomotor routines which support perceptual judgments, similar to the well-established exploratory routines for haptic perception. In a first study, observers saw different scenes with two objects presented in a photorealistic virtual reality environment. Observers were asked to judge which of two objects was taller or wider while gaze was tracked. All tasks were performed with the same set of virtual objects in the same scenes, so that we can compare spatial characteristics of exploratory gaze behavior to quantify oculomotor routines for each task. Width judgments showed fixations around the center of the objects with larger horizontal spread. In contrast, for height judgments, gaze was shifted towards the top of the objects with larger vertical spread. These results suggest specific strategies in gaze behavior that presumably are used for perceptual judgments. To test the causal link between oculomotor behavior and perception, in a second study, observers either could freely gaze at the object or we introduced a gaze contingent set up forcing observers to fixate specific positions on the object. Discrimination performance was similar between free gaze and the gaze contingent conditions for width and height judgments. These results suggest that although gaze is adapted for different tasks, performance seems to be based on a perceptual strategy, independent of potential cues that can be provided by the oculomotor system.

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bioRxiv2023

Sensorimotor Confidence for Tracking Eye Movements

For successful interactions with the world, we often have to evaluate our own performance. Such metacognitive evaluations have been studied with perceptual decisions, but much less with respect to the evaluation of our own actions. While eye movements are one of the most frequent actions we perform, we are typically unaware of them. Here, we investigated if there is any evidence for metacognitive sensitivity for the accuracy of eye movements. Participants tracked a dot cloud as it followed an unpredictable sinusoidal trajectory for six seconds, and then reported if they thought their performance was better or worse than their average tracking performance. Our results show above chance identification of better tracking behavior across all trials and also for repeated attempts of the same target trajectories. While the sensitivity in discriminating performance between better and worse trials was stable across sessions, for their judgements participants relied more on performance in the final seconds of each trial. This behavior matched previous reports when judging the quality of hand movements, although overall metacognitive sensitivity for eye movements was significantly lower. Together, these results provide an additional piece of evidence for sensorimotor confidence, and open interesting questions about why it differs across actions and how it could be related to other instances of confidence. Statement of RelevanceIn everyday life, it is often critical to be able to evaluate the quality of our own cognitive decisions and actions. However, one of our most frequent actions often does not even reach our awareness: eye movements. We investigated whether observers were able to successfully judge the accuracy of their eye movements when tracking a cloud of dots that followed an unpredictable trajectory. We found that observers were able to distinguish good from bad trials, although sensitivity was lower compared to equivalent previous reports when judging the quality of hand movements. These results add an item to the growing list of our metacognitive abilities, but critically for eye movements that we are typically unaware of. They lead to important novel questions about why metacognitive abilities differ across decisions or different types of actions, and what the potential components of metacognitive abilities might be.

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bioRxiv2023

Cues for predictive eye movements in naturalistic scenes

We previously compared following of the same trajectories with eye movements, but either as an isolated target or embedded in a naturalistic scene, in this case the movement of a puck in an ice hockey game. We observed that the oculomotor system was able to leverage the contextual cues available in the naturalistic scene to produce predictive eye movements. In this study we wanted to assess which factors are critical for achieving this predictive advantage by manipulating four factors: the expertise of the viewers, the amount of available peripheral information, and contextual and kinematic cues. The more peripheral information became available (by manipulating the area of the video that was visible), the better the predictions of all observers. However, expert ice hockey fans were consistently more accurate and better at predicting than novices and also benefitted more from additional peripheral information. Artificial contextual cues about the position of the players did not lead to a predictive advantage, whereas impairing the causal structure of kinematic cues by playing the video in reverse led to a severe impairment. When the videos were flipped vertically to introduce more difficult kinematic cues, predictive behavior was comparable to when observers watching the original videos. Together, these results demonstrate that when contextual information is available in naturalistic scenes, the oculomotor system is successfully integrating them, and is not only relying on low-level information about the target trajectory. Critical factors for successful prediction seem to be the amount of available information, experience with the stimuli and the availability of intact kinematic cues for player movements.

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bioRxiv2019

HD-tDCS over mIPS causally modulates online reach correction

Brain lesion and stimulation studies have suggested posterior parietal cortex and the medial intraparietal sulcus in particular as a crucial hub for online movement error corrections. However, causal evidence for this is still sparse. Indeed, lesion studies are potentially confounded by compensatory reorganization mechanisms while brain stimulation studies have produced heterogeneous results when employing transcranial magnetic stimulation. Here we designed a new complementary paradigm using fMRI-guided high-definition transcranial direct current stimulation (HD-tDCS) of the left medial intraparietal sulcus (mIPS) together with regression-based mediation analysis to re-examine the causal role of mIPS in online reach corrections to jumping targets. We obtained two independent measures of stimulation-induced changes in brain activity by modeling current flow in the brain and through EEG recordings before and after HD-tDCS stimulation. Third, to quantify behavioral effects of HD-tDCS we computed movement curvature as a measure of online correction. We demonstrate that both of our measurements of brain activity were consistent with a polarity-specific modulation of the online correction for targets jumping to the contralateral side of the stimulation. Importantly, using a mediation analysis of the relationship between stimulation current and movement curvature suggests that the induced current modifies brain activity, which then leads to the observed behavioral changes. This unique combination of methods and analysis thus provides complementary evidence for the crucial role of the posterior parietal cortex in online error correction, while at the same time setting a new methodological standard with respect to the causal influence of transcranial direct current stimulation. New & NoteworthyTranscranial direct current stimulation (tDCS) is an interesting and potentially useful tool for asking causal scientific questions and design clinical treatments. With our unique combination of highly accurate fMRI guided stimulation, current forward modeling, EEG recordings before and after the stimulation and behavioral changes we could unravel the causal structure of tDCS. Our approach naturally deals with the variability of tDCS results, increasing its potential usefulness as a tool for research and clinical applications.

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