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Nature Communications Sep 2021In spite of the reduced visual acuity, parafoveal information plays an important role in natural reading. However, competing models on reading disagree on whether words...
In spite of the reduced visual acuity, parafoveal information plays an important role in natural reading. However, competing models on reading disagree on whether words are previewed parafoveally at the lexical level. We find neural evidence for lexical parafoveal processing by combining a rapid invisible frequency tagging (RIFT) approach with magnetoencephalography (MEG) and eye-tracking. In a silent reading task, target words are tagged (flickered) subliminally at 60 Hz. The tagging responses measured when fixating on the pre-target word reflect parafoveal processing of the target word. We observe stronger tagging responses during pre-target fixations when followed by low compared with high lexical frequency targets. Moreover, this lexical parafoveal processing is associated with individual reading speed. Our findings suggest that reading unfolds in the fovea and parafovea simultaneously to support fluent reading.
Topics: Eye Movements; Female; Fixation, Ocular; Fovea Centralis; Humans; Macula Lutea; Male; Models, Neurological; Reading; Visual Cortex; Visual Perception; Young Adult
PubMed: 34475391
DOI: 10.1038/s41467-021-25571-x -
Journal of Vision Aug 2021Face processing is a fast and efficient process due to its evolutionary and social importance. A majority of people direct their first eye movement to a featureless...
Face processing is a fast and efficient process due to its evolutionary and social importance. A majority of people direct their first eye movement to a featureless point just below the eyes that maximizes accuracy in recognizing a person's identity and gender. Yet, the exact properties or features of the face that guide the first eye movements and reduce fixational variability are unknown. Here, we manipulated the presence of the facial features and the spatial configuration of features to investigate their effect on the location and variability of first and second fixations to peripherally presented faces. Our results showed that observers can utilize the face outline, individual facial features, and feature spatial configuration to guide the first eye movements to their preferred point of fixation. The eyes have a preferential role in guiding the first eye movements and reducing fixation variability. Eliminating the eyes or altering their position had the greatest influence on the location and variability of fixations and resulted in the largest detriment to face identification performance. The other internal features (nose and mouth) also contribute to reducing fixation variability. A subsequent experiment measuring detection of single features showed that the eyes have the highest detectability (relative to other features) in the visual periphery providing a strong sensory signal to guide the oculomotor system. Together, the results suggest a flexible multiple-cue approach that might be a robust solution to cope with how the varying eccentricities in the real world influence the ability to resolve individual feature properties and the preferential role of the eyes.
Topics: Eye; Eye Movements; Facial Recognition; Fixation, Ocular; Humans
PubMed: 34347018
DOI: 10.1167/jov.21.8.7 -
Investigative Ophthalmology & Visual... Jan 2021The most common form of strabismus, intermittent exotropia, is thought to become manifest when the drive to fuse is overcome by excessive divergent muscle tone. This... (Comparative Study)
Comparative Study
PURPOSE
The most common form of strabismus, intermittent exotropia, is thought to become manifest when the drive to fuse is overcome by excessive divergent muscle tone. This principle is tested by examining the alignment of the eyes in the absence of vision. We compare the ocular deviation in patients with intermittent exotropia under conditions of monocular versus binocular occlusion.
METHODS
This prospective study of a patient cohort referred to our laboratory enrolled 18 patients with typical findings of well-controlled intermittent exotropia. Eye positions were recorded with video eye trackers while patients looked at a fixation spot at a distance of 57 cm. One eye was occluded, and the resulting ocular deviation was measured. Both eyes were then occluded, and the ocular deviation was re-measured.
RESULTS
The majority of patients (11/18) had a smaller deviation when both eyes were covered. Occlusion of one eye resulted in a mean exotropia of 13.5° ± 4.7°. Occlusion of both eyes reduced the mean exotropia to 6.0° ± 6.5° (paired t-test, P < 0.001), corresponding to a 56% reduction in the ocular deviation. This reduction persisted during prolonged bilateral occlusion but reversed as soon as vision was restored.
CONCLUSIONS
Bilateral occlusion reveals a fixation-free state of alignment that is different from orthotropia and usually less than the exotropia that occurs spontaneously during binocular viewing. This finding demonstrates that the deviation angle in patients with intermittent exotropia is actively mediated by visual feedback, which the fixating eye is capable of providing alone.
Topics: Adolescent; Adult; Child; Exotropia; Eye Movements; Female; Fixation, Ocular; Humans; Male; Middle Aged; Prospective Studies; Sensory Deprivation; Vision, Binocular; Vision, Monocular; Young Adult
PubMed: 33393972
DOI: 10.1167/iovs.62.1.6 -
Journal of Vision Oct 2021Due to the dramatic difference in spatial resolution between the central fovea and the surrounding retinal regions, accurate fixation on important objects is critical...
Due to the dramatic difference in spatial resolution between the central fovea and the surrounding retinal regions, accurate fixation on important objects is critical for humans. It is known that the preferred retinal location (PRL) for fixation of healthy human observers rarely coincides with the retinal location with the highest cone density. It is not currently known, however, whether the PRL is consistent within an observer or is subject to fluctuations and, moreover, whether observers' subjective fixation location coincides with the PRL. We studied whether the PRL changes between days. We used an adaptive optics scanning laser ophthalmoscope to project a Maltese cross fixation target on an observer's retina and continuously imaged the exact retinal location of the target. We found that observers consistently use the same PRL across days, regardless of how much the PRL is displaced from the cone density peak location. We then showed observers small stimuli near the visual field location on which they fixated, and the observers judged whether or not the stimuli appeared in fixation. Observers' precision in this task approached that of fixation itself. Observers based their judgment on both the visual scene coordinates and the retinal location of the stimuli. We conclude that the PRL in a normally functioning visual system is fixed, and observers use it as a reference point in judging stimulus locations.
Topics: Fixation, Ocular; Fovea Centralis; Humans; Ophthalmoscopes; Retina; Scotoma; Visual Fields
PubMed: 34643658
DOI: 10.1167/jov.21.11.9 -
Journal of Vision Dec 2022In general, humans preferentially look at conspecifics in naturalistic images. However, such group-based effects might conceal systematic individual differences...
In general, humans preferentially look at conspecifics in naturalistic images. However, such group-based effects might conceal systematic individual differences concerning the preference for social information. Here, we investigated to what degree fixations on social features occur consistently within observers and whether this preference generalizes to other measures of social prioritization in the laboratory as well as the real world. Participants carried out a free viewing task, a relevance taps task that required them to actively select image regions that are crucial for understanding a given scene, and they were asked to freely take photographs outside the laboratory that were later classified regarding their social content. We observed stable individual differences in the fixation and active selection of human heads and faces that were correlated across tasks and partly predicted the social content of self-taken photographs. Such relationship was not observed for human bodies indicating that different social elements need to be dissociated. These findings suggest that idiosyncrasies in the visual exploration and interpretation of social features exist and predict real-world behavior. Future studies should further characterize these preferences and elucidate how they shape perception and interpretation of social contexts in healthy participants and patients with mental disorders that affect social functioning.
Topics: Humans; Fixation, Ocular; Attention
PubMed: 36583910
DOI: 10.1167/jov.22.13.10 -
Journal of Neurology Dec 2022Downbeat nystagmus (DBN) is a common form of acquired fixation nystagmus related to vestibulo-cerebellar impairments and associated with impaired vision and postural...
Downbeat nystagmus (DBN) is a common form of acquired fixation nystagmus related to vestibulo-cerebellar impairments and associated with impaired vision and postural imbalance. DBN intensity becomes modulated by various factors such as gaze direction, head position, daytime, and resting conditions. Further evidence suggests that locomotion attenuates postural symptoms in DBN. Here, we examined whether walking might analogously influence ocular-motor deficits in DBN. Gaze stabilization mechanisms and nystagmus frequency were examined in 10 patients with DBN and 10 age-matched healthy controls with visual fixation during standing vs. walking on a motorized treadmill. Despite their central ocular-motor deficits, linear and angular gaze stabilization in the vertical plane were functional during walking in DBN patients and comparable to controls. Notably, nystagmus frequency in patients was considerably reduced during walking compared to standing (p < 0.001). The frequency of remaining nystagmus during walking was further modulated in a manner that depended on the specific phase of the gait cycle (p = 0.015). These attenuating effects on nystagmus intensity during walking suggest that ocular-motor control disturbances are selectively suppressed during locomotion in DBN. This suppression is potentially mediated by locomotor efference copies that have been shown to selectively govern gaze stabilization during stereotyped locomotion in animal models.
Topics: Animals; Nystagmus, Pathologic; Fixation, Ocular; Walking; Cerebellum; Vision, Ocular
PubMed: 35412151
DOI: 10.1007/s00415-022-11106-x -
Journal of Vision Oct 2020Macular degeneration (MD), a retinal disease affecting central vision, represents the leading cause of visual impairment in the Western world, and MD patients face...
Macular degeneration (MD), a retinal disease affecting central vision, represents the leading cause of visual impairment in the Western world, and MD patients face severe limitations in daily activities like reading and face recognition. A common compensation strategy adopted by these patients involves the use of a region in the spared peripheral retina as a new fixation spot and oculomotor reference (preferred retinal locus, or PRL). Still, peripheral vision is characterized by poorer visual acuity, fixation stability, and larger crowding zones that further hinder processes like object recognition, visual search, and reading. Perceptual learning (PL) has been successfully used to improve visual acuity in mild visual conditions (e.g., presbyopia, amblyopia and myopia), but results in MD are less clear, often showing limited generalization of learning, unlike what is observed in a healthy population. A possible reason is the suboptimal fixation in the PRL that might prevent patients from processing the briefly presented training stimuli. Following this hypothesis, we trained five MD patients and four age- and eccentricity-matched controls with a protocol that combined contrast detection and a task previously used to train fixation stability. Results showed transfer of learning to crowding reduction, reading speed, and visual acuity in both MD patients and controls. These results suggest that in the case of central vision loss, PL training might benefit from the integration of oculomotor components to optimize the effect of training and promote transfer of learning to other visual functions.
Topics: Aged; Aged, 80 and over; Female; Fixation, Ocular; Humans; Learning; Macular Degeneration; Male; Middle Aged; Perceptual Masking; Scotoma; Vision, Low; Visual Acuity; Visual Perception
PubMed: 33064123
DOI: 10.1167/jov.20.10.19 -
Quarterly Journal of Experimental... Feb 2023This study examined the cognitive processes involved in reading vertically and horizontally mirrored text. We tracked participants' eye movements while they were reading...
This study examined the cognitive processes involved in reading vertically and horizontally mirrored text. We tracked participants' eye movements while they were reading the Potsdam Sentence Corpus which consists of 144 sentences with target words that are manipulated for length and frequency. Sentences were presented in three different conditions: In the normal condition, text was presented with upright letters, in the vertical condition, each letter was flipped around its vertical (left-right) axis while in the horizontal condition, letters were flipped around their horizontal (up-down) axis. Results show that reading was slowed down in both mirror conditions and that horizontal mirroring was particularly disruptive. In both conditions, we found larger effects of word length than in the normal condition indicating that participants read the sentences more serially and effortfully. Similarly, frequency effects were larger in both mirror conditions in later reading measures (gaze duration, go-past time, and total reading time) and particularly pronounced in the horizontal condition. This indicates that reading mirrored script involves a late checking mechanism that is particularly important for reading a horizontally mirrored script. Together, our findings demonstrate that mirroring affects both early visual identification and later linguistic processes.
Topics: Humans; Eye Movements; Pattern Recognition, Visual; Linguistics; Language; Fixation, Ocular
PubMed: 35230211
DOI: 10.1177/17470218221085943 -
Applied Ergonomics Nov 2021Certain font features (e.g., letter width) can change the amount of space occupied by text in published works. Font styles/features are also known to affect reading eye...
Certain font features (e.g., letter width) can change the amount of space occupied by text in published works. Font styles/features are also known to affect reading eye movements (EM); however, few studies have examined these effects - and none used high-resolution displays. We examined the effects of font width on EMs by utilizing four fonts, from the Univers family, which varied in letter-width magnitude. Participants' (n = 25) reading speed, saccade velocity, and the duration/number of fixations and saccades were recorded. The Ultra Condensed font significantly influenced readability and yielded: fewer fixations and saccades; longer fixation durations than the Roman and Extended fonts; and shorter saccade durations, relative to the other fonts. Readers efficiently adjusted their EMs such that no reading-speed differences were observed. The eye-tracking metrics revealed two trade-off effects: (1) fewer and shorter EMs and (2) more and longer EMs, which were revealed by the font-width manipulation.
Topics: Comprehension; Eye Movements; Fixation, Ocular; Humans; Reading; Saccades; Time Factors
PubMed: 34225106
DOI: 10.1016/j.apergo.2021.103523 -
Scientific Reports May 2020About one-third of autistic people have limited ability to use speech. Some have learned to communicate by pointing to letters of the alphabet. But this method is...
About one-third of autistic people have limited ability to use speech. Some have learned to communicate by pointing to letters of the alphabet. But this method is controversial because it requires the assistance of another person-someone who holds a letterboard in front of users and so could theoretically cue them to point to particular letters. Indeed, some scientists have dismissed the possibility that any nonspeaking autistic person who communicates with assistance could be conveying their own thoughts. In the study reported here, we used head-mounted eye-tracking to investigate communicative agency in a sample of nine nonspeaking autistic letterboard users. We measured the speed and accuracy with which they looked at and pointed to letters as they responded to novel questions. Participants pointed to about one letter per second, rarely made spelling errors, and visually fixated most letters about half a second before pointing to them. Additionally, their response times reflected planning and production processes characteristic of fluent spelling in non-autistic typists. These findings render a cueing account of participants' performance unlikely: The speed, accuracy, timing, and visual fixation patterns suggest that participants pointed to letters they selected themselves, not letters they were directed to by the assistant. The blanket dismissal of assisted autistic communication is therefore unwarranted.
Topics: Adolescent; Adult; Autistic Disorder; Communication; Eye Movements; Female; Fixation, Ocular; Humans; Language; Male; Reaction Time; Speech; Surveys and Questionnaires; Young Adult
PubMed: 32398782
DOI: 10.1038/s41598-020-64553-9