Curveball: A tool for rapid measurement of contrast sensitivity based on smooth eye movements.
Ontology highlight
ABSTRACT:
SUBMITTER: Mooney SWJ
PROVIDER: S-EPMC6238984 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Previous studies have reported that concurrent manual tracking enhances smooth pursuit eye movements only when tracking a self-driven or a predictable moving target. Here, we used a control-theoretic approach to examine whether concurrent manual tracking enhances smooth pursuit of an unpredictable moving target. In the eye-hand tracking condition, participants used their eyes to track a Gaussian target that moved randomly along a horizontal axis. In the meantime, they used their dominant hand to move a mouse to control the horizontal movement of a Gaussian cursor to vertically align it with the target. In the eye-alone tracking condition, the target and cursor positions recorded in the eye-hand tracking condition were replayed, and participants only performed eye tracking of the target. Catch-up saccades were identified and removed from the recorded eye movements, allowing for a frequency-response analysis of the smooth pursuit response to unpredictable target motion. We found that the overall smooth pursuit gain was higher and the number of catch-up saccades made was less when eye tracking was accompanied by manual tracking than when not. We conclude that concurrent manual tracking enhances smooth pursuit. This enhancement is a fundamental property of eye-hand coordination that occurs regardless of the predictability of the target motion.
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Project description:Anticipatory smooth eye movements were studied in response to expectations of motion of random-dot kinematograms (RDKs). Dot lifetime was limited (52-208 ms) to prevent selection and tracking of the motion of local elements and to disrupt the perception of an object moving across space. Anticipatory smooth eye movements were found in response to cues signaling the future direction of global RDK motion, either prior to the onset of the RDK or prior to a change in its direction of motion. Cues signaling the lifetime of the dots were not effective. These results show that anticipatory smooth eye movements can be produced by expectations of global motion and do not require a sustained representation of an object or set of objects moving across space. At the same time, certain properties of global motion (direction) were more sensitive to cues than others (dot lifetime), suggesting that the rules by which prediction operates to influence pursuit may go beyond simple associations between cues and the upcoming motion of targets.
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Project description:Smooth pursuit eye movements are important for vision because they maintain the line of sight on targets that move smoothly within the visual field. Smooth pursuit is driven by neural representations of motion, including a surprisingly strong influence of high-level signals representing expected motion. We studied anticipatory smooth eye movements (defined as smooth eye movements in the direction of expected future motion) produced by salient visual cues in a group of high-functioning observers with Autism Spectrum Disorder (ASD), a condition that has been associated with difficulties in either generating predictions, or translating predictions into effective motor commands. Eye movements were recorded while participants pursued the motion of a disc that moved within an outline drawing of an inverted Y-shaped tube. The cue to the motion path was a visual barrier that blocked the untraveled branch (right or left) of the tube. ASD participants showed strong anticipatory smooth eye movements whose velocity was the same as that of a group of neurotypical participants. Anticipatory smooth eye movements appeared on the very first cued trial, indicating that trial-by-trial learning was not responsible for the responses. These results are significant because they show that anticipatory capacities are intact in high-functioning ASD in cases where the cue to the motion path is highly salient and unambiguous. Once the ability to generate anticipatory pursuit is demonstrated, the study of the anticipatory responses with a variety of types of cues provides a window into the perceptual or cognitive processes that underlie the interpretation of events in natural environments or social situations.
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Project description:Patients with schizophrenia as well as individuals with high levels of schizotypy are known to have deficits in smooth pursuit eye movements (SPEM). Here, we investigated, for the first time, the neural mechanisms underlying SPEM performance in high schizotypy. Thirty-one healthy participants [N?=?19 low schizotypes, N?=?12 high schizotypes (HS)] underwent functional magnetic resonance imaging at 3T with concurrent oculographic recording while performing a SPEM task with sinusoidal stimuli at two velocities (0.2 and 0.4 Hz). Behaviorally, a significant interaction between schizotypy group and velocity was found for frequency of saccades during SPEM, indicating impairments in HS in the slow but not the fast condition. On the neural level, HS demonstrated lower brain activation in different regions of the occipital lobe known to be associated with early sensory and attentional processing and motion perception (V3A, middle occipital gyrus, and fusiform gyrus). This group difference in neural activation was independent of target velocity. Together, these findings replicate the observation of altered pursuit performance in highly schizotypal individuals and, for the first time, identify brain activation patterns accompanying these performance changes. These posterior activation differences are compatible with evidence of motion processing deficits from the schizophrenia literature and, therefore, suggest overlap between schizotypy and schizophrenia both on cognitive-perceptual and neurophysiological levels. However, deficits in frontal motor areas observed during pursuit in schizophrenia were not seen here, suggesting the operation of additional genetic and/or illness-related influences in the clinical disorder.
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Project description:Smooth pursuit eye movements (pursuit) are used to minimize the retinal motion of moving objects. During pursuit, the pattern of motion on the retina carries not only information about the object movement but also reafferent information about the eye movement itself. The latter arises from the retinal flow of the stationary world in the direction opposite to the eye movement. To extract the global direction of motion of the tracked object and stationary world, the visual system needs to integrate ambiguous local motion measurements (i.e., the aperture problem). Unlike the tracked object, the stationary world's global motion is entirely determined by the eye movement and thus can be approximately derived from motor commands sent to the eye (i.e., from an efference copy). Because retinal motion opposite to the eye movement is dominant during pursuit, different motion integration mechanisms might be used for retinal motion in the same direction and opposite to pursuit. To investigate motion integration during pursuit, we tested direction discrimination of a brief change in global object motion. The global motion stimulus was a circular array of small static apertures within which one-dimensional gratings moved. We found increased coherence thresholds and a qualitatively different reflexive ocular tracking for global motion opposite to pursuit. Both effects suggest reduced sampling of motion opposite to pursuit, which results in an impaired ability to extract coherence in motion signals in the reafferent direction. We suggest that anisotropic motion integration is an adaptation to asymmetric retinal motion patterns experienced during pursuit eye movements. NEW & NOTEWORTHY This study provides a new understanding of how the visual system achieves coherent perception of an object's motion while the eyes themselves are moving. The visual system integrates local motion measurements to create a coherent percept of object motion. An analysis of perceptual judgments and reflexive eye movements to a brief change in an object's global motion confirms that the visual and oculomotor systems pick fewer samples to extract global motion opposite to the eye movement.
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Project description:Eye movements alter visual perceptions in a number of ways. During smooth-pursuit eye movements, previous studies reported decreased detection threshold for colored stimuli and for high-spatial-frequency luminance stimuli, suggesting a boost in the parvocellular system. The present study investigated the underlying neural mechanism using EEG in human participants. Participants followed a moving target with smooth-pursuit eye movements while steady-state visually evoked potentials (SSVEPs) were elicited by equiluminant red-green flickering gratings in the background. SSVEP responses to colored gratings were 18.9% higher during smooth pursuit than during fixation. There was no enhancement of SSVEPs by smooth pursuit when the flickering grating was defined by luminance instead of color. This result provides physiological evidence that the chromatic response in the visual system is boosted by the execution of smooth-pursuit eye movements in humans. Because the response improvement is thought to be the result of an improved response in the parvocellular system, SSVEPs to equiluminant stimuli could provide a direct test of parvocellular signaling, especially in populations where collecting an explicit behavioral response from the participant is not feasible.NEW & NOTEWORTHY We constantly move our eyes when we explore the world. Eye movements alter visual perception in various ways. The smooth-pursuit eye movements have been shown to boost color sensitivity. We recorded steady-state visually evoked potentials to equiluminant chromatic flickering stimuli and observed increased steady-state visually evoked potentials when participants smoothly pursued a moving target compared with when they maintained fixation. This work provides direct neurophysiological evidence for the parvocellular boost by smooth-pursuit eye movements in humans.
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Project description:The smooth pursuit eye movement system incorporates various control features enabling adaptation to specific tracking situations. In this work, we analyzed the interplay between two of these mechanisms: gain control and predictive pursuit. We tested human responses to high-frequency perturbations during step-ramp pursuit, as well as the pursuit of a periodically moving target. For the latter task, we found a nonlinear interaction between perturbation response and carrier acceleration. Responses to perturbations where the initial perturbation acceleration was contradirectional to carrier acceleration increased with carrier velocity, in a manner similar to that observed during step-ramp pursuit. In contrast, responses to perturbations with ipsidirectional initial perturbation and carrier acceleration were large for all carrier velocities. Modeling the pursuit system suggests that gain control and short-term prediction are separable elements. The observed effect may be explained by combining the standard gain control mechanism with a derivative-based short-term predictive mechanism. The nonlinear interaction between perturbation and carrier acceleration can be reproduced by assuming a signal saturation, which is acting on the derivative of the target velocity signal. Our results therefore argue for the existence of an internal estimate of target acceleration as a basis for a simple yet efficient short-term predictive mechanism.
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