1
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Melnyk K, Friedman L, Komogortsev OV. What can entropy metrics tell us about the characteristics of ocular fixation trajectories? PLoS One 2024; 19:e0291823. [PMID: 38166054 PMCID: PMC10760742 DOI: 10.1371/journal.pone.0291823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Accepted: 09/06/2023] [Indexed: 01/04/2024] Open
Abstract
In this study, we provide a detailed analysis of entropy measures calculated for fixation eye movement trajectories from the three different datasets. We employed six key metrics (Fuzzy, Increment, Sample, Gridded Distribution, Phase, and Spectral Entropies). We calculate these six metrics on three sets of fixations: (1) fixations from the GazeCom dataset, (2) fixations from what we refer to as the "Lund" dataset, and (3) fixations from our own research laboratory ("OK Lab" dataset). For each entropy measure, for each dataset, we closely examined the 36 fixations with the highest entropy and the 36 fixations with the lowest entropy. From this, it was clear that the nature of the information from our entropy metrics depended on which dataset was evaluated. These entropy metrics found various types of misclassified fixations in the GazeCom dataset. Two entropy metrics also detected fixation with substantial linear drift. For the Lund dataset, the only finding was that low spectral entropy was associated with what we call "bumpy" fixations. These are fixations with low-frequency oscillations. For the OK Lab dataset, three entropies found fixations with high-frequency noise which probably represent ocular microtremor. In this dataset, one entropy found fixations with linear drift. The between-dataset results are discussed in terms of the number of fixations in each dataset, the different eye movement stimuli employed, and the method of eye movement classification.
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Affiliation(s)
- Kateryna Melnyk
- Department of Computer Science, Texas State University, San Marcos, TX, United States of America
| | - Lee Friedman
- Department of Computer Science, Texas State University, San Marcos, TX, United States of America
| | - Oleg V. Komogortsev
- Department of Computer Science, Texas State University, San Marcos, TX, United States of America
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2
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Raju MH, Friedman L, Bouman TM, Komogortsev OV. Determining Which Sine Wave Frequencies Correspond to Signal and Which Correspond to Noise in Eye-Tracking Time-Series. J Eye Mov Res 2023; 14:10.16910/jemr.14.3.5. [PMID: 38957345 PMCID: PMC11217914 DOI: 10.16910/jemr.14.3.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/04/2024] Open
Abstract
The Fourier theorem states that any time-series can be decomposed into a set of sinusoidal frequencies, each with its own phase and amplitude. The literature suggests that some frequencies are important to reproduce key qualities of eye-movements ("signal") and some of frequencies are not important ("noise"). To investigate what is signal and what is noise, we analyzed our dataset in three ways: (1) visual inspection of plots of saccade, microsaccade and smooth pursuit exemplars; (2) analysis of the percentage of variance accounted for (PVAF) in 1,033 unfiltered saccade trajectories by each frequency band; (3) analyzing the main sequence relationship between saccade peak velocity and amplitude, based on a power law fit. Visual inspection suggested that frequencies up to 75 Hz are required to represent microsaccades. Our PVAF analysis indicated that signals in the 0-25 Hz band account for nearly 100% of the variance in saccade trajectories. Power law coefficients (a, b) return to unfiltered levels for signals low-pass filtered at 75 Hz or higher. We conclude that to maintain eyemovement signal and reduce noise, a cutoff frequency of 75 Hz is appropriate. We explain why, given this finding, a minimum sampling rate of 750 Hz is suggested.
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Affiliation(s)
- Mehedi H. Raju
- Department of Computer Science Texas State University San Marcos, Texas, USA
| | - Lee Friedman
- Department of Computer Science Texas State University San Marcos, Texas, USA
| | - Troy M. Bouman
- Department of Mechanical Engineering-Engineering Mechanics Michigan Technological University Houghton, MI, USA
| | - Oleg V. Komogortsev
- Department of Computer Science Texas State University San Marcos, Texas, USA
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3
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Graham L, Das J, Vitorio R, McDonald C, Walker R, Godfrey A, Morris R, Stuart S. Ocular microtremor: a structured review. Exp Brain Res 2023; 241:2191-2203. [PMID: 37632535 PMCID: PMC10471653 DOI: 10.1007/s00221-023-06691-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 08/16/2023] [Indexed: 08/28/2023]
Abstract
Ocular microtremor (OMT) is the smallest of three involuntary fixational micro eye movements, which has led to it being under researched in comparison. The link between OMT and brain function generates a strong rationale for further study as there is potential for its use as a biomarker in populations with neurological injury and disease. This structured review focused on populations previously studied, instrumentation used for measurement, commonly reported OMT outcomes, and recommendations concerning protocol design and future studies. Current methods of quantifying OMT will be reviewed to analyze their efficacy and efficiency and guide potential development and understanding of novel techniques. Electronic databases were systematically searched and compared with predetermined inclusion criteria. 216 articles were identified in the search and screened by two reviewers. 16 articles were included for review. Findings showed that piezoelectric probe is the most common method of measuring OMT, with fewer studies involving non-invasive approaches, such as contact lenses and laser imaging. OMT frequency was seen to be reduced during general anesthesia at loss of consciousness and in neurologically impaired participants when compared to healthy adults. We identified the need for a non-invasive technique for measuring OMT and highlight its potential in clinical applications as an objective biomarker for neurological assessments. We highlight the need for further research on the clinical validation of OMT to establish its potential to identify or predict a meaningful clinical or functional state, specifically, regarding accuracy, precision, and reliability of OMT.
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Affiliation(s)
- Lisa Graham
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle upon Tyne, UK
- Gateshead Health NHS Foundation Trust, Gateshead, UK
| | - Julia Das
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle upon Tyne, UK
- Northumbria Healthcare NHS Foundation Trust, North Shields, UK
| | - Rodrigo Vitorio
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle upon Tyne, UK
| | | | - Richard Walker
- Northumbria Healthcare NHS Foundation Trust, North Shields, UK
| | - Alan Godfrey
- Department of Computer and Information Science, Northumbria University, Newcastle upon Tyne, UK
| | - Rosie Morris
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle upon Tyne, UK
- Northumbria Healthcare NHS Foundation Trust, North Shields, UK
| | - Samuel Stuart
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle upon Tyne, UK.
- Northumbria Healthcare NHS Foundation Trust, North Shields, UK.
- Department of Neurology, Oregon Health & Science University, Portland, OR, USA.
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4
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Holmqvist K, Örbom SL, Hooge ITC, Niehorster DC, Alexander RG, Andersson R, Benjamins JS, Blignaut P, Brouwer AM, Chuang LL, Dalrymple KA, Drieghe D, Dunn MJ, Ettinger U, Fiedler S, Foulsham T, van der Geest JN, Hansen DW, Hutton SB, Kasneci E, Kingstone A, Knox PC, Kok EM, Lee H, Lee JY, Leppänen JM, Macknik S, Majaranta P, Martinez-Conde S, Nuthmann A, Nyström M, Orquin JL, Otero-Millan J, Park SY, Popelka S, Proudlock F, Renkewitz F, Roorda A, Schulte-Mecklenbeck M, Sharif B, Shic F, Shovman M, Thomas MG, Venrooij W, Zemblys R, Hessels RS. Eye tracking: empirical foundations for a minimal reporting guideline. Behav Res Methods 2023; 55:364-416. [PMID: 35384605 PMCID: PMC9535040 DOI: 10.3758/s13428-021-01762-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 45.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/29/2021] [Indexed: 11/08/2022]
Abstract
In this paper, we present a review of how the various aspects of any study using an eye tracker (such as the instrument, methodology, environment, participant, etc.) affect the quality of the recorded eye-tracking data and the obtained eye-movement and gaze measures. We take this review to represent the empirical foundation for reporting guidelines of any study involving an eye tracker. We compare this empirical foundation to five existing reporting guidelines and to a database of 207 published eye-tracking studies. We find that reporting guidelines vary substantially and do not match with actual reporting practices. We end by deriving a minimal, flexible reporting guideline based on empirical research (Section "An empirically based minimal reporting guideline").
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Affiliation(s)
- Kenneth Holmqvist
- Department of Psychology, Nicolaus Copernicus University, Torun, Poland.
- Department of Computer Science and Informatics, University of the Free State, Bloemfontein, South Africa.
- Department of Psychology, Regensburg University, Regensburg, Germany.
| | - Saga Lee Örbom
- Department of Psychology, Regensburg University, Regensburg, Germany
| | - Ignace T C Hooge
- Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands
| | - Diederick C Niehorster
- Lund University Humanities Lab and Department of Psychology, Lund University, Lund, Sweden
| | - Robert G Alexander
- Department of Ophthalmology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
| | | | - Jeroen S Benjamins
- Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands
- Social, Health and Organizational Psychology, Utrecht University, Utrecht, The Netherlands
| | - Pieter Blignaut
- Department of Computer Science and Informatics, University of the Free State, Bloemfontein, South Africa
| | | | - Lewis L Chuang
- Department of Ergonomics, Leibniz Institute for Working Environments and Human Factors, Dortmund, Germany
- Institute of Informatics, LMU Munich, Munich, Germany
| | | | - Denis Drieghe
- School of Psychology, University of Southampton, Southampton, UK
| | - Matt J Dunn
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK
| | | | - Susann Fiedler
- Vienna University of Economics and Business, Vienna, Austria
| | - Tom Foulsham
- Department of Psychology, University of Essex, Essex, UK
| | | | - Dan Witzner Hansen
- Machine Learning Group, Department of Computer Science, IT University of Copenhagen, Copenhagen, Denmark
| | | | - Enkelejda Kasneci
- Human-Computer Interaction, University of Tübingen, Tübingen, Germany
| | | | - Paul C Knox
- Department of Eye and Vision Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| | - Ellen M Kok
- Department of Education and Pedagogy, Division Education, Faculty of Social and Behavioral Sciences, Utrecht University, Utrecht, The Netherlands
- Department of Online Learning and Instruction, Faculty of Educational Sciences, Open University of the Netherlands, Heerlen, The Netherlands
| | - Helena Lee
- University of Southampton, Southampton, UK
| | - Joy Yeonjoo Lee
- School of Health Professions Education, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Jukka M Leppänen
- Department of Psychology and Speed-Language Pathology, University of Turku, Turku, Finland
| | - Stephen Macknik
- Department of Ophthalmology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
| | - Päivi Majaranta
- TAUCHI Research Center, Computing Sciences, Faculty of Information Technology and Communication Sciences, Tampere University, Tampere, Finland
| | - Susana Martinez-Conde
- Department of Ophthalmology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
| | - Antje Nuthmann
- Institute of Psychology, University of Kiel, Kiel, Germany
| | - Marcus Nyström
- Lund University Humanities Lab, Lund University, Lund, Sweden
| | - Jacob L Orquin
- Department of Management, Aarhus University, Aarhus, Denmark
- Center for Research in Marketing and Consumer Psychology, Reykjavik University, Reykjavik, Iceland
| | - Jorge Otero-Millan
- Herbert Wertheim School of Optometry and Vision Science, University of California, Berkeley, CA, USA
| | - Soon Young Park
- Comparative Cognition, Messerli Research Institute, University of Veterinary Medicine Vienna, Medical University of Vienna, Vienna, Austria
| | - Stanislav Popelka
- Department of Geoinformatics, Palacký University Olomouc, Olomouc, Czech Republic
| | - Frank Proudlock
- The University of Leicester Ulverscroft Eye Unit, Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, UK
| | - Frank Renkewitz
- Department of Psychology, University of Erfurt, Erfurt, Germany
| | - Austin Roorda
- Herbert Wertheim School of Optometry and Vision Science, University of California, Berkeley, CA, USA
| | | | - Bonita Sharif
- School of Computing, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
| | - Frederick Shic
- Center for Child Health, Behavior and Development, Seattle Children's Research Institute, Seattle, WA, USA
- Department of General Pediatrics, University of Washington School of Medicine, Seattle, WA, USA
| | - Mark Shovman
- Eyeviation Systems, Herzliya, Israel
- Department of Industrial Design, Bezalel Academy of Arts and Design, Jerusalem, Israel
| | - Mervyn G Thomas
- The University of Leicester Ulverscroft Eye Unit, Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, UK
| | - Ward Venrooij
- Electrical Engineering, Mathematics and Computer Science (EEMCS), University of Twente, Enschede, The Netherlands
| | | | - Roy S Hessels
- Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands
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5
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Tang R, Chen W, Wang Y. Different roles of subcortical inputs in V1 responses to luminance and contrast. Eur J Neurosci 2021; 53:3710-3726. [PMID: 33848389 DOI: 10.1111/ejn.15233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 04/02/2021] [Accepted: 04/09/2021] [Indexed: 01/01/2023]
Abstract
Cells in the primary visual cortex (V1) generally respond weakly to large uniform luminance stimuli. Only a subset of V1 cells is thought to encode uniform luminance information. In natural scenes, local luminance is an important feature for defining an object that varies and coexists with local spatial contrast. However, the strategies used by V1 cells to encode local mean luminance for spatial contrast stimuli remain largely unclear. Here, using extracellular recordings in anesthetized cats, we investigated the responses of V1 cells by comparing with those of retinal ganglion (RG) cells and lateral geniculate nucleus (LGN) cells to simultaneous and rapid changes in luminance and spatial contrast. Almost all V1 cells exhibited a strong monotonic increasing luminance tuning when they were exposed to high spatial contrast. Thus, V1 cells encode the luminance carried by spatial contrast stimuli with the monotonically increasing response function. Moreover, high contrast decreased luminance tuning of OFF cells but increased that of in ON cells in RG and LGN. The luminance and contrast tunings of LGN ON cells were highly separable as V1 cells, whereas those of LGN OFF cells were lowly separable. These asymmetrical effects of spatial contrast on ON/OFF channels might underlie the robust ability of V1 cells to perform luminance tuning when exposed to spatial contrast stimuli.
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Affiliation(s)
- Rendong Tang
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Wenzhen Chen
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yi Wang
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
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6
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Abstract
Due to its reported high sampling frequency and precision, the Tobii Pro Spectrum is of potential interest to researchers who want to study small eye movements during fixation. We test how suitable the Tobii Pro Spectrum is for research on microsaccades by computing data-quality measures and common properties of microsaccades and comparing these to the currently most used system in this field: the EyeLink 1000 Plus. Results show that the EyeLink data provide higher RMS precision and microsaccade rates compared with data acquired with the Tobii Pro Spectrum. However, both systems provide microsaccades with similar directions and shapes, as well as rates consistent with previous literature. Data acquired at 1200 Hz with the Tobii Pro Spectrum provide results that are more similar to the EyeLink, compared to data acquired at 600 Hz. We conclude that the Tobii Pro Spectrum is a useful tool for researchers investigating microsaccades.
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7
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Sadeghpour S, Otero-Millan J. Torsional component of microsaccades during fixation and quick phases during optokinetic stimulation. J Eye Mov Res 2020; 13. [PMID: 33828810 PMCID: PMC8010913 DOI: 10.16910/jemr.13.5.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
While many studies have characterized the eye movements during visual fixation, includ-ing microsaccades, in most cases only horizontal and vertical components have been rec-orded and analyzed. Thus, little is known about the torsional component of microsaccades. We took advantage of a newly developed software and hardware to record eye movements around the three axes of rotation during fixation and torsional optokinetic stimulus. We found that the average amplitude of the torsional component of microsaccades during fixation was 0.34 ± 0.07 degrees with velocities following a main sequence with a slope comparable to the horizontal and vertical components. We also found the size of the tor-sional displacement during microsaccades was correlated with the horizontal but not the vertical component. In the presence of an optokinetic stimulus a nystagmus was induced producing a more frequent and larger torsional quick phases compared to microsaccades produced during fixation with a stationary stimulus. The torsional component and the vertical vergence component of quick phases grew larger with higher velocities. Addition-ally, our results validate and show the feasibility of recording torsional eye movements using video eye tracking in a desktop mounted setup.
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8
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Abstract
Saccadic eye movements can allude to emotional states and visual attention. Recent studies have shown that microsaccadic responses (i.e., small fixational eye movements) reflect advanced brain activity during attentional and cognitive tasks. Moreover, the microsaccadic activity related to emotional attention provides new insights into this field. For example, emotional pictures attenuate the microsaccadic rate, and microsaccadic responses to covert attention occur in the direction opposite to a negative emotional target. However, the effects of various emotional events on microsaccadic activity remain debatable. This review introduces visual attention and eye movement studies that support findings on the modulation of microsaccadic responses to emotional events, comparing them with typical microsaccadic responses. This review also discusses the brain neuronal mechanisms governing microsaccadic responses to the attentional shifts triggered by emotion-related stimuli. It is hard to reveal the direct brain pathway of the microsaccadic modulation, especially in advanced (e.g., sustained anger, envy, distrust, guilt, frustration, delight, attraction, trust, and love), but also in basic human emotions (i.e., anger, disgust, fear, happiness, sadness, and surprise). However, non-human primates and human studies can uncover the possible brain pathways of emotional attention and microsaccades, thus providing future research directions. In particular, the facilitated (or reduced) attention is common evidence that microsaccadic activities change under a variety of social modalities (e.g., cognition, music, mental illness, and working memory) that elicit emotions and feelings.
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Affiliation(s)
- Koji Kashihara
- College of Information Science and Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga, 525-8577, Japan.
- Graduate School of Technology, Industrial and Social Sciences, Tokushima University, 2-1 Minamijyousanjima, Tokushima, 770-8506, Japan.
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9
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Roberts MJ, Lange G, Van Der Veen T, Lowet E, De Weerd P. The Attentional Blink is Related to the Microsaccade Rate Signature. Cereb Cortex 2019; 29:5190-5203. [PMID: 30941400 DOI: 10.1093/cercor/bhz058] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 02/26/2019] [Accepted: 03/02/2019] [Indexed: 11/15/2022] Open
Abstract
The reduced detectability of a target T2 following discrimination of a preceding target T1 in the attentional blink (AB) paradigm is classically interpreted as a consequence of reduced attention to T2 due to attentional allocation to T1. Here, we investigated whether AB was related to changes in microsaccade rate (MSR). We found a pronounced MSR signature following T1 onset, characterized by MSR suppression from 200 to 328 ms and enhancement from 380 to 568 ms. Across participants, the magnitude of the MSR suppression correlated with the AB effect such that low T2 detectability corresponded to reduced MSR. However, in the same task, T1 error trials coincided with the presence of microsaccades. We discuss this apparent paradox in terms of known neurophysiological correlates of MS whereby cortical excitability is suppressed both during the microsaccade and MSR suppression, in accordance to poor T1 performance with microsaccade occurrence and poor T2 performance with microsaccade absence. Our data suggest a novel low-level mechanism contributing to AB characterized by reduced MSR, thought to cause suppressed visual cortex excitability. This opens the question of whether attention mediates T2 performance suppression independently from MSR, and if not, how attention interacts with MSR to produce the T2 performance suppression.
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Affiliation(s)
- Mark J Roberts
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Gesa Lange
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Tracey Van Der Veen
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Eric Lowet
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands.,Department of Biology, Boston University, Boston, MA, USA
| | - Peter De Weerd
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands.,Maastricht Centre for Systems Biology (MaCSBio), Faculty of Science and Engineering, Maastricht, The Netherlands
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10
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Abstract
This work presents a visual analytics approach to explore microsaccade distributions in high-frequency eye tracking data. Research studies often apply filter algorithms and parameter values for microsaccade detection. Even when the same algorithms are employed, different parameter values might be adopted across different studies. In this paper, we present a visual analytics system (VisME) to promote reproducibility in the data analysis of microsaccades. It allows users to interactively vary the parametric values for microsaccade filters and evaluate the resulting influence on microsaccade behavior across individuals and on a group level. In particular, we exploit brushing-and-linking techniques that allow the microsaccadic properties of space, time, and movement direction to be extracted, visualized, and compared across multiple views. We demonstrate in a case study the use of our visual analytics system on data sets collected from natural scene viewing and show in a qualitative usability study the usefulness of this approach for eye tracking researchers. We believe that interactive tools such as VisME will promote greater transparency in eye movement research by providing researchers with the ability to easily understand complex eye tracking data sets; such tools can also serve as teaching systems. VisME is provided as open source software.
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11
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Barnhart AS, Costela FM, Martinez-Conde S, Macknik SL, Goldinger SD. Microsaccades reflect the dynamics of misdirected attention in magic. J Eye Mov Res 2019; 12. [PMID: 33828753 PMCID: PMC7962680 DOI: 10.16910/jemr.12.6.7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The methods of magicians provide powerful tools for enhancing the ecological validity of laboratory studies of attention. The current research borrows a technique from magic to explore the relationship between microsaccades and covert attention under near-natural viewing conditions. We monitored participants’ eye movements as they viewed a magic trick where a coin placed beneath a napkin vanishes and reappears beneath another napkin. Many participants fail to see the coin move from one location to the other the first time around, thanks to the magician’s misdirection. However, previous research was unable to distinguish whether or not participants were fooled based on their eye movements. Here, we set out to determine if microsaccades may provide a window into the efficacy of the magician’s misdirection. In a multi-trial setting, participants monitored the location of the coin (which changed positions in half of the trials), while engaging in a delayed match-to-sample task at a different spatial location. Microsaccades onset times varied with task difficulty, and microsaccade directions indexed the locus of covert attention. Our combined results indicate that microsaccades may be a useful metric of covert attentional processes in applied and ecologically valid settings.
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Affiliation(s)
| | - Francisco M Costela
- Schepens Eye Research Institute, Harvard Medical School, Boston, Massachusetts, USA
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12
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Martinez-Conde S, Macknik SL. Unchanging visions: the effects and limitations of ocular stillness. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0204. [PMID: 28242737 DOI: 10.1098/rstb.2016.0204] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/19/2016] [Indexed: 11/12/2022] Open
Abstract
Scientists have pondered the perceptual effects of ocular motion, and those of its counterpart, ocular stillness, for over 200 years. The unremitting 'trembling of the eye' that occurs even during gaze fixation was first noted by Jurin in 1738. In 1794, Erasmus Darwin documented that gaze fixation produces perceptual fading, a phenomenon rediscovered in 1804 by Ignaz Paul Vital Troxler. Studies in the twentieth century established that Jurin's 'eye trembling' consisted of three main types of 'fixational' eye movements, now called microsaccades (or fixational saccades), drifts and tremor. Yet, owing to the constant and minute nature of these motions, the study of their perceptual and physiological consequences has met significant technological challenges. Studies starting in the 1950s and continuing in the present have attempted to study vision during retinal stabilization-a technique that consists on shifting any and all visual stimuli presented to the eye in such a way as to nullify all concurrent eye movements-providing a tantalizing glimpse of vision in the absence of change. No research to date has achieved perfect retinal stabilization, however, and so other work has devised substitute ways to counteract eye motion, such as by studying the perception of afterimages or of the entoptic images formed by retinal vessels, which are completely stable with respect to the eye. Yet other research has taken the alternative tack to control eye motion by behavioural instruction to fix one's gaze or to keep one's gaze still, during concurrent physiological and/or psychophysical measurements. Here, we review the existing data-from historical and contemporary studies that have aimed to nullify or minimize eye motion-on the perceptual and physiological consequences of perfect versus imperfect fixation. We also discuss the accuracy, quality and stability of ocular fixation, and the bottom-up and top-down influences that affect fixation behaviour.This article is part of the themed issue 'Movement suppression: brain mechanisms for stopping and stillness'.
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Affiliation(s)
- Susana Martinez-Conde
- Department of Ophthalmology, State University of New York (SUNY) Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA
| | - Stephen L Macknik
- Department of Ophthalmology, State University of New York (SUNY) Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA
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13
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Costela FM, McCamy MB, Coffelt M, Otero-Millan J, Macknik SL, Martinez-Conde S. Changes in visibility as a function of spatial frequency and microsaccade occurrence. Eur J Neurosci 2017; 45:433-439. [PMID: 27891684 DOI: 10.1111/ejn.13487] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 11/07/2016] [Accepted: 11/21/2016] [Indexed: 11/28/2022]
Abstract
Fixational eye movements (FEMs), including microsaccades, drift, and tremor, shift our eye position during ocular fixation, producing retinal motion that is thought to help visibility by counteracting neural adaptation to unchanging stimulation. Yet, how each FEM type influences this process is still debated. Recent studies found little to no relationship between microsaccades and visual perception of spatial frequencies (SF). However, these conclusions were based on coarse analyses that make it hard to appreciate the actual effects of microsaccades on target visibility as a function of SF. Thus, how microsaccades contribute to the visibility of stimuli of different SFs remains unclear. Here, we asked how the visibility of targets of various SFs changed over time, in relationship with concurrent microsaccade production. Participants continuously reported on changes in target visibility, allowing us to time-lock ongoing changes in microsaccade parameters to perceptual transitions in visibility. Microsaccades restored/increased the visibility of low SF targets more efficiently than that of high SF targets. Yet, microsaccade rates rose before periods of increased visibility, and dropped before periods of diminished visibility, for all the SFs tested, suggesting that microsaccades boosted target visibility across a wide range of SFs. Our data also indicate that visual stimuli fade/become harder to see less often in the presence of microsaccades. In addition, larger microsaccades restored/increased target visibility more effectively than smaller microsaccades. These combined results support the proposal that microsaccades enhance visibility across a broad variety of SFs.
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Affiliation(s)
- Francisco M Costela
- Harvard Medical School, Schepens Eye Research Institute, Boston, MA, USA.,Interdisciplinary Graduate program in Neuroscience, Arizona State University, Tempe, AZ, USA.,Barrow Neurological Institute, Phoenix, AZ, USA
| | - Michael B McCamy
- Barrow Neurological Institute, Phoenix, AZ, USA.,Grand Canyon University, Phoenix, AZ, USA
| | - Mary Coffelt
- Barrow Neurological Institute, Phoenix, AZ, USA.,Department of Biomedical Engineering, University of Arizona, Tucson, AZ, USA
| | - Jorge Otero-Millan
- Barrow Neurological Institute, Phoenix, AZ, USA.,Department of Neurology, Johns Hopkins University, Baltimore, MD, USA
| | - Stephen L Macknik
- Barrow Neurological Institute, Phoenix, AZ, USA.,Downstate Medical Center, State University of New York, Brooklyn, NY, 11203, USA
| | - Susana Martinez-Conde
- Barrow Neurological Institute, Phoenix, AZ, USA.,Downstate Medical Center, State University of New York, Brooklyn, NY, 11203, USA
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14
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Troncoso XG, McCamy MB, Jazi AN, Cui J, Otero-Millan J, Macknik SL, Costela FM, Martinez-Conde S. V1 neurons respond differently to object motion versus motion from eye movements. Nat Commun 2015; 6:8114. [PMID: 26370518 PMCID: PMC4579399 DOI: 10.1038/ncomms9114] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 07/21/2015] [Indexed: 11/10/2022] Open
Abstract
How does the visual system differentiate self-generated motion from motion in the external world? Humans can discern object motion from identical retinal image displacements induced by eye movements, but the brain mechanisms underlying this ability are unknown. Here we exploit the frequent production of microsaccades during ocular fixation in the primate to compare primary visual cortical responses to self-generated motion (real microsaccades) versus motion in the external world (object motion mimicking microsaccades). Real and simulated microsaccades were randomly interleaved in the same viewing condition, thereby producing equivalent oculomotor and behavioural engagement. Our results show that real microsaccades generate biphasic neural responses, consisting of a rapid increase in the firing rate followed by a slow and smaller-amplitude suppression that drops below baseline. Simulated microsaccades generate solely excitatory responses. These findings indicate that V1 neurons can respond differently to internally and externally generated motion, and expand V1's potential role in information processing and visual stability during eye movements. A key question in neuroscience is understanding how the brain distinguishes self-generated motion from motion in the external world. Here the authors demonstrate that the response of primary visual cortical neurons to a moving stimulus depends on whether the motion was self- or externally generated.
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Affiliation(s)
- Xoana G Troncoso
- Barrow Neurological Institute, 350 W Thomas Road, Phoenix, Arizona 85013, USA.,UNIC-CNRS (Unité de Neuroscience Information et Complexité, Centre National de la Recherche Scientifique), 1 Avenue de la Terrase, 91198 Gif-sur-Yvette, France
| | - Michael B McCamy
- Barrow Neurological Institute, 350 W Thomas Road, Phoenix, Arizona 85013, USA
| | - Ali Najafian Jazi
- Barrow Neurological Institute, 350 W Thomas Road, Phoenix, Arizona 85013, USA.,Program in Neuroscience, Arizona State University, PO Box 874601, Tempe, Arizona 85287, USA
| | - Jie Cui
- Barrow Neurological Institute, 350 W Thomas Road, Phoenix, Arizona 85013, USA
| | - Jorge Otero-Millan
- Barrow Neurological Institute, 350 W Thomas Road, Phoenix, Arizona 85013, USA.,Department of Neurology, Johns Hopkins University, 600 N Wolfe Street, Baltimore, Maryland 21287, USA
| | - Stephen L Macknik
- Barrow Neurological Institute, 350 W Thomas Road, Phoenix, Arizona 85013, USA.,State University of New York (SUNY) Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, New York 11203, USA
| | - Francisco M Costela
- Barrow Neurological Institute, 350 W Thomas Road, Phoenix, Arizona 85013, USA.,Program in Neuroscience, Arizona State University, PO Box 874601, Tempe, Arizona 85287, USA
| | - Susana Martinez-Conde
- Barrow Neurological Institute, 350 W Thomas Road, Phoenix, Arizona 85013, USA.,State University of New York (SUNY) Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, New York 11203, USA
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15
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Characteristics of Spontaneous Square-Wave Jerks in the Healthy Macaque Monkey during Visual Fixation. PLoS One 2015; 10:e0126485. [PMID: 26067994 PMCID: PMC4466238 DOI: 10.1371/journal.pone.0126485] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2014] [Accepted: 04/02/2015] [Indexed: 11/19/2022] Open
Abstract
Saccadic intrusions (SIs), predominantly horizontal saccades that interrupt accurate fixation, include square-wave jerks (SWJs; the most common type of SI), which consist of an initial saccade away from the fixation target followed, after a short delay, by a return saccade that brings the eye back onto target. SWJs are present in most human subjects, but are prominent by their increased frequency and size in certain parkinsonian disorders and in recessive, hereditary spinocerebellar ataxias. SWJs have been also documented in monkeys with tectal and cerebellar etiologies, but no studies to date have investigated the occurrence of SWJs in healthy nonhuman primates. Here we set out to determine the characteristics of SWJs in healthy rhesus macaques (Macaca mulatta) during attempted fixation of a small visual target. Our results indicate that SWJs are common in healthy nonhuman primates. We moreover found primate SWJs to share many characteristics with human SWJs, including the relationship between the size of a saccade and its likelihood to be part of a SWJ. One main discrepancy between monkey and human SWJs was that monkey SWJs tended to be more vertical than horizontal, whereas human SWJs have a strong horizontal preference. Yet, our combined data indicate that primate and human SWJs play a similar role in fixation correction, suggesting that they share a comparable coupling mechanism at the oculomotor generation level. These findings constrain the potential brain areas and mechanisms underlying the generation of fixational saccades in human and nonhuman primates.
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16
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McCamy MB, Otero-Millan J, Leigh RJ, King SA, Schneider RM, Macknik SL, Martinez-Conde S. Simultaneous recordings of human microsaccades and drifts with a contemporary video eye tracker and the search coil technique. PLoS One 2015; 10:e0128428. [PMID: 26035820 PMCID: PMC4452707 DOI: 10.1371/journal.pone.0128428] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 04/27/2015] [Indexed: 11/29/2022] Open
Abstract
Human eyes move continuously, even during visual fixation. These “fixational eye movements” (FEMs) include microsaccades, intersaccadic drift and oculomotor tremor. Research in human FEMs has grown considerably in the last decade, facilitated by the manufacture of noninvasive, high-resolution/speed video-oculography eye trackers. Due to the small magnitude of FEMs, obtaining reliable data can be challenging, however, and depends critically on the sensitivity and precision of the eye tracking system. Yet, no study has conducted an in-depth comparison of human FEM recordings obtained with the search coil (considered the gold standard for measuring microsaccades and drift) and with contemporary, state-of-the art video trackers. Here we measured human microsaccades and drift simultaneously with the search coil and a popular state-of-the-art video tracker. We found that 95% of microsaccades detected with the search coil were also detected with the video tracker, and 95% of microsaccades detected with video tracking were also detected with the search coil, indicating substantial agreement between the two systems. Peak/mean velocities and main sequence slopes of microsaccades detected with video tracking were significantly higher than those of the same microsaccades detected with the search coil, however. Ocular drift was significantly correlated between the two systems, but drift speeds were higher with video tracking than with the search coil. Overall, our combined results suggest that contemporary video tracking now approaches the search coil for measuring FEMs.
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Affiliation(s)
- Michael B. McCamy
- Barrow Neurological Institute, Phoenix, Arizona, United States of America
- * E-mail: (MBM); (SMC)
| | - Jorge Otero-Millan
- Barrow Neurological Institute, Phoenix, Arizona, United States of America
- Department of Signal Theory and Communications, University of Vigo, Vigo, Spain
- Department of Neurology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - R. John Leigh
- Veterans Affairs Medical Center, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Susan A. King
- Veterans Affairs Medical Center, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Rosalyn M. Schneider
- Veterans Affairs Medical Center, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Stephen L. Macknik
- Barrow Neurological Institute, Phoenix, Arizona, United States of America
- SUNY Downstate Medical Center, Brooklyn, New York, United States of America
| | - Susana Martinez-Conde
- Barrow Neurological Institute, Phoenix, Arizona, United States of America
- SUNY Downstate Medical Center, Brooklyn, New York, United States of America
- * E-mail: (MBM); (SMC)
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17
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Ryle JP, Vohnsen B, Sheridan JT. Simultaneous drift, microsaccades, and ocular microtremor measurement from a single noncontact far-field optical sensor. JOURNAL OF BIOMEDICAL OPTICS 2015; 20:27004. [PMID: 25674709 DOI: 10.1117/1.jbo.20.2.027004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 01/16/2015] [Indexed: 06/04/2023]
Abstract
We report on the combined far-field measurement of the three involuntary eye movements, drift, microsaccades, and ocular microtremor (OMT), using a noncontact far-field optical method. We review the significance of the smallest and least measured, and thus least understood, of the three, OMT. Using modern digital imaging techniques, we perform detailed analysis, present experimental results, and examine the extracted parameters using a noncontact far-field sensor. For the first time, in vivo noncontact measurements of all fixational in-plane movements of the human eye are reported, which simultaneously provide both the horizontal (left-right) and vertical (up-down) displacement results.
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Affiliation(s)
- James P Ryle
- Maynooth University, The Callan Institute, Department of Electronic Engineering, Maynooth, County Kildare, Republic of Ireland
| | - Brian Vohnsen
- University College Dublin, College of Science, School of Physics, Belfield, Dublin 4, Republic of Ireland
| | - John T Sheridan
- University College Dublin, College of College of Engineering & Architecture, School of Electrical, Electronic and Communications Engineering, Communications and Optoelectronic Research Centre, SFI Strategic Research Cluster in Solar Energy Conversion, Bel
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18
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Ghasia FF, Shaikh AG. Experimental tests of hypotheses for microsaccade generation. Exp Brain Res 2015; 233:1089-95. [PMID: 25563497 DOI: 10.1007/s00221-014-4188-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2014] [Accepted: 12/18/2014] [Indexed: 12/10/2023]
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19
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Why have microsaccades become larger? Investigating eye deformations and detection algorithms. Vision Res 2014; 118:17-24. [PMID: 25481631 DOI: 10.1016/j.visres.2014.11.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 11/15/2014] [Accepted: 11/21/2014] [Indexed: 11/20/2022]
Abstract
The reported size of microsaccades is considerably larger today compared to the initial era of microsaccade studies during the 1950s and 1960s. We investigate whether this increase in size is related to the fact that the eye-trackers of today measure different ocular structures than the older techniques, and that the movements of these structures may differ during a microsaccade. In addition, we explore the impact such differences have on subsequent analyzes of the eye-tracker signals. In Experiment I, the movement of the pupil as well as the first and fourth Purkinje reflections were extracted from series of eye images recorded during a fixation task. Results show that the different ocular structures produce different microsaccade signatures. In Experiment II, we found that microsaccade amplitudes computed with a common detection algorithm were larger compared to those reported by two human experts. The main reason was that the overshoots were not systematically detected by the algorithm and therefore not accurately accounted for. We conclude that one reason to why the reported size of microsaccades has increased is due to the larger overshoots produced by the modern pupil-based eye-trackers compared to the systems used in the classical studies, in combination with the lack of a systematic algorithmic treatment of the overshoot. We hope that awareness of these discrepancies in microsaccade dynamics across eye structures will lead to more generally accepted definitions of microsaccades.
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20
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Costela FM, Otero-Millan J, McCamy MB, Macknik SL, Troncoso XG, Jazi AN, Crook SM, Martinez-Conde S. Fixational eye movement correction of blink-induced gaze position errors. PLoS One 2014; 9:e110889. [PMID: 25333481 PMCID: PMC4205003 DOI: 10.1371/journal.pone.0110889] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 09/24/2014] [Indexed: 11/18/2022] Open
Abstract
Our eyes move continuously. Even when we attempt to fix our gaze, we produce “fixational” eye movements including microsaccades, drift and tremor. The potential role of microsaccades versus drifts in the control of eye position has been debated for decades and remains in question today. Here we set out to determine the corrective functions of microsaccades and drifts on gaze-position errors due to blinks in non-human primates (Macaca mulatta) and humans. Our results show that blinks contribute to the instability of gaze during fixation, and that microsaccades, but not drifts, correct fixation errors introduced by blinks. These findings provide new insights about eye position control during fixation, and indicate a more general role of microsaccades in fixation correction than thought previously.
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Affiliation(s)
- Francisco M. Costela
- Barrow Neurological Institute, Phoenix, Arizona, United States of America
- Interdisciplinary Graduate program in Neuroscience, Arizona State University, Phoenix, Arizona, United States of America
| | - Jorge Otero-Millan
- Barrow Neurological Institute, Phoenix, Arizona, United States of America
- Department of Neurology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Michael B. McCamy
- Barrow Neurological Institute, Phoenix, Arizona, United States of America
| | - Stephen L. Macknik
- Barrow Neurological Institute, Phoenix, Arizona, United States of America
- Department of Ophthalmology, State University of New York Downstate Medical Center, Brooklyn, New York, United States of America
| | - Xoana G. Troncoso
- Barrow Neurological Institute, Phoenix, Arizona, United States of America
- Unité de Neuroscience, Information et Complexité (CNRS-UNIC), UPR CNRS 3293, Gif-sur-Yvette, France
| | - Ali Najafian Jazi
- Barrow Neurological Institute, Phoenix, Arizona, United States of America
| | - Sharon M. Crook
- School of Mathematical and Statistical Sciences and School of Life Sciences, Arizona State University, Phoenix, Arizona, United States of America
| | - Susana Martinez-Conde
- Barrow Neurological Institute, Phoenix, Arizona, United States of America
- Department of Ophthalmology, State University of New York Downstate Medical Center, Brooklyn, New York, United States of America
- * E-mail:
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21
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Otero-Millan J, Macknik SL, Martinez-Conde S. Fixational eye movements and binocular vision. Front Integr Neurosci 2014; 8:52. [PMID: 25071480 PMCID: PMC4083562 DOI: 10.3389/fnint.2014.00052] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 06/03/2014] [Indexed: 11/13/2022] Open
Abstract
During attempted visual fixation, small involuntary eye movements-called fixational eye movements-continuously change of our gaze's position. Disagreement between the left and right eye positions during such motions can produce diplopia (double vision). Thus, the ability to properly coordinate the two eyes during gaze fixation is critical for stable perception. For the last 50 years, researchers have studied the binocular characteristics of fixational eye movements. Here we review classical and recent studies on the binocular coordination (i.e., degree of conjugacy) of each fixational eye movement type: microsaccades, drift and tremor, and its perceptual contribution to increasing or reducing binocular disparity. We also discuss how amblyopia and other visual pathologies affect the binocular coordination of fixational eye movements.
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Affiliation(s)
- Jorge Otero-Millan
- Department of Neurobiology, Barrow Neurological Institute Phoenix, AZ, USA ; Department of Neurology, Johns Hopkins University Baltimore, MD, USA
| | - Stephen L Macknik
- Department of Neurobiology, Barrow Neurological Institute Phoenix, AZ, USA ; Department of Neurosurgery, Barrow Neurological Institute Phoenix, AZ, USA
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22
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Kenny E, Coakley D, Boyle G. Non-contact in vivo measurement of ocular microtremor using laser speckle correlation metrology. Physiol Meas 2014; 35:1229-43. [PMID: 24853319 DOI: 10.1088/0967-3334/35/7/1229] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Ocular microtremor (OMT) is a small involuntary eye movement present in all subjects. In this paper we present the results of in vivo OMT measurement using a novel non-contact laser speckle technique. OMT signals have not previously been measured from the sclera using this laser speckle correlation technique. To verify the system's ability to record eye movements, it is first tested using a large angle eye rotation. Next, the system is tested with a group of 20 subjects and OMT parameters are extracted. The results of OMT measurements gave a mean frequency of 78 ± 3.86 Hz and peak-to-peak amplitude of 21.42 ± 7.01 µrad, these values are consistent with known values from eye-contacting methods.
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Affiliation(s)
- E Kenny
- Mercer's Institute for Research on Ageing, St. James's Hospital, Dublin 8, Ireland
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23
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Highly informative natural scene regions increase microsaccade production during visual scanning. J Neurosci 2014; 34:2956-66. [PMID: 24553936 DOI: 10.1523/jneurosci.4448-13.2014] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Classical image statistics, such as contrast, entropy, and the correlation between central and nearby pixel intensities, are thought to guide ocular fixation targeting. However, these statistics are not necessarily task relevant and therefore do not provide a complete picture of the relationship between informativeness and ocular targeting. Moreover, it is not known whether either informativeness or classical image statistics affect microsaccade production; thus, the role of microsaccades in information acquisition is also unknown. The objective quantification of the informativeness of a scene region is a major challenge, because it can vary with both image features and the task of the viewer. Thus, previous definitions of informativeness suffered from subjectivity and inconsistency across studies. Here we developed an objective measure of informativeness based on fixation consistency across human observers, which accounts for both bottom-up and top-down influences in ocular targeting. We then analyzed fixations in more versus less informative image regions in relation to classical statistics. Observers generated more microsaccades on more informative than less informative image regions, and such regions also exhibited low redundancy in their classical statistics. Increased microsaccade production was not explained by increased fixation duration, suggesting that the visual system specifically uses microsaccades to heighten information acquisition from informative regions.
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24
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25
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26
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Siegenthaler E, Costela FM, McCamy MB, Di Stasi LL, Otero-Millan J, Sonderegger A, Groner R, Macknik S, Martinez-Conde S. Task difficulty in mental arithmetic affects microsaccadic rates and magnitudes. Eur J Neurosci 2013; 39:287-94. [DOI: 10.1111/ejn.12395] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 09/19/2013] [Indexed: 10/26/2022]
Affiliation(s)
- Eva Siegenthaler
- Department of Neurobiology; Barrow Neurological Institute; Phoenix AZ USA
| | - Francisco M. Costela
- Department of Neurobiology; Barrow Neurological Institute; Phoenix AZ USA
- Interdisciplinary Graduate Program in Neuroscience; Arizona State University; Tempe AZ USA
| | - Michael B. McCamy
- Department of Neurobiology; Barrow Neurological Institute; Phoenix AZ USA
| | - Leandro L. Di Stasi
- Department of Neurobiology; Barrow Neurological Institute; Phoenix AZ USA
- Cognitive Ergonomics Group; Mind, Brain, and Behavior Research Center (CIMCYC); University of Granada Granada Spain
- Joint Center University of Granada - Spanish Army Training and Doctrine Command; Spain
| | - Jorge Otero-Millan
- Department of Neurobiology; Barrow Neurological Institute; Phoenix AZ USA
- Johns Hopkins University; Department of Neurology; Baltimore MD USA
| | | | - Rudolf Groner
- Department of Psychology; University of Bern; Bern Switzerland
| | - Stephen Macknik
- Department of Neurobiology; Barrow Neurological Institute; Phoenix AZ USA
- Department of Neurosurgery; Barrow Neurological Institute; Phoenix AZ USA
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27
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Roberts JA, Wallis G, Breakspear M. Fixational eye movements during viewing of dynamic natural scenes. Front Psychol 2013; 4:797. [PMID: 24194727 PMCID: PMC3810780 DOI: 10.3389/fpsyg.2013.00797] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 10/09/2013] [Indexed: 11/13/2022] Open
Abstract
Even during periods of fixation our eyes undergo small amplitude movements. These movements are thought to be essential to the visual system because neural responses rapidly fade when images are stabilized on the retina. The considerable recent interest in fixational eye movements (FEMs) has thus far concentrated on idealized experimental conditions with artificial stimuli and restrained head movements, which are not necessarily a suitable model for natural vision. Natural dynamic stimuli, such as movies, offer the potential to move beyond restrictive experimental settings to probe the visual system with greater ecological validity. Here, we study FEMs recorded in humans during the unconstrained viewing of a dynamic and realistic visual environment, revealing that drift trajectories exhibit the properties of a random walk with memory. Drifts are correlated at short time scales such that the gaze position diverges from the initial fixation more quickly than would be expected for an uncorrelated random walk. We propose a simple model based on the premise that the eye tends to avoid retracing its recent steps to prevent photoreceptor adaptation. The model reproduces key features of the observed dynamics and enables estimation of parameters from data. Our findings show that FEM correlations thought to prevent perceptual fading exist even in highly dynamic real-world conditions.
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Affiliation(s)
- James A Roberts
- Systems Neuroscience Group, QIMR Berghofer Medical Research Institute Herston, QLD, Australia
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28
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Costela FM, McCamy MB, Macknik SL, Otero-Millan J, Martinez-Conde S. Microsaccades restore the visibility of minute foveal targets. PeerJ 2013; 1:e119. [PMID: 23940832 PMCID: PMC3740150 DOI: 10.7717/peerj.119] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 07/10/2013] [Indexed: 11/30/2022] Open
Abstract
Stationary targets can fade perceptually during steady visual fixation, a phenomenon known as Troxler fading. Recent research found that microsaccades—small, involuntary saccades produced during attempted fixation—can restore the visibility of faded targets, both in the visual periphery and in the fovea. Because the targets tested previously extended beyond the foveal area, however, the ability of microsaccades to restore the visibility of foveally-contained targets remains unclear. Here, subjects reported the visibility of low-to-moderate contrast targets contained entirely within the fovea during attempted fixation. The targets did not change physically, but their visibility varied intermittently during fixation, in an illusory fashion (i.e., foveal Troxler fading). Microsaccade rates increased significantly before the targets became visible, and decreased significantly before the targets faded, for a variety of target contrasts. These results support previous research linking microsaccade onsets to the visual restoration of peripheral and foveal targets, and extend the former conclusions to minute targets contained entirely within the fovea. Our findings suggest that the involuntary eye movements produced during attempted fixation do not always prevent fading—in either the fovea or the periphery—and that microsaccades can restore perception, when fading does occur. Therefore, microsaccades are relevant to human perception of foveal stimuli.
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Affiliation(s)
- Francisco M Costela
- Department of Neurobiology, Barrow Neurological Institute , Phoenix, AZ , USA ; Graduate Program in Neuroscience, Arizona State University , Tempe, AZ , USA
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29
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Di Stasi LL, McCamy MB, Catena A, Macknik SL, Cañas JJ, Martinez-Conde S. Microsaccade and drift dynamics reflect mental fatigue. Eur J Neurosci 2013; 38:2389-98. [PMID: 23675850 DOI: 10.1111/ejn.12248] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 04/01/2013] [Accepted: 04/03/2013] [Indexed: 11/28/2022]
Abstract
Our eyes are always in motion. Even during periods of relative fixation we produce so-called 'fixational eye movements', which include microsaccades, drift and tremor. Mental fatigue can modulate saccade dynamics, but its effects on microsaccades and drift are unknown. Here we asked human subjects to perform a prolonged and demanding visual search task (a simplified air traffic control task), with two difficulty levels, under both free-viewing and fixation conditions. Saccadic and microsaccadic velocity decreased with time-on-task whereas drift velocity increased, suggesting that ocular instability increases with mental fatigue. Task difficulty did not influence eye movements despite affecting reaction times, performance errors and subjective complexity ratings. We propose that variations in eye movement dynamics with time-on-task are consistent with the activation of the brain's sleep centers in correlation with mental fatigue. Covariation of saccadic and microsaccadic parameters moreover supports the hypothesis of a common generator for microsaccades and saccades. We conclude that changes in fixational and saccadic dynamics can indicate mental fatigue due to time-on-task, irrespective of task complexity. These findings suggest that fixational eye movement dynamics have the potential to signal the nervous system's activation state.
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Affiliation(s)
- Leandro L Di Stasi
- Department of Neurobiology, Barrow Neurological Institute, Phoenix, AZ, USA
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30
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Leigh RJ, Martinez-Conde S. Tremor of the eyes, or of the head, in Parkinson's disease? Mov Disord 2013; 28:691-3. [PMID: 23629728 PMCID: PMC3739927 DOI: 10.1002/mds.25478] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 03/14/2013] [Indexed: 01/14/2023] Open
Affiliation(s)
- R John Leigh
- Neurology Service, Veterans Affairs Medical CenterCleveland, Ohio, USA
- Department of Neurology, Case Medical Center, Case Western Reserve UniversityCleveland, Ohio, USA
- *Correspondence to: Dr. R. John Leigh, M.D. Department of Neurology, Case Medical Center, 11100 Euclid Avenue, Cleveland, OH 44106;
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