Displaying publications 1 - 20 of 26 in total

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  1. Fulltext Eye movements are made to the centre of gravity of texture-defined targets
    Sidhu SK, Allen HA, Keeble DRT
    Vision Res, 2023 Sep;210:108264.
    PMID: 37276684 DOI: 10.1016/j.visres.2023.108264
    Saccadic localisation of targets of various properties has been extensively studied, but rarely for texture-defined figures. In this paper, three experiments that investigate the way information from a texture target is processed in order to provide a signal for eye movement control are presented. Participants made saccades to target regions embedded in a background structure, and the saccade landing position and latency were measured. The textures comprised line elements, with orientations of the lines configured to form the figure and ground. Various orientation profile configurations (Block, Blur, and Cornsweet), were used in order to measure the role of edge profiles in driving eye movements and producing salience. We found that in all cases the visual system is in fact able to effectively segregate a texture figure from the ground in order to accurately plan a saccade to the target-figure. While saccadic latency was the highest for the Blur profile, the mean saccadic landing position was mostly unaffected by the various profiles (Experiment 1). More specifically, we showed that saccades were directed to the centre-of-gravity of the target (Experiment 2). We also found that figures with information of orientation contrast at both the edge and centre of figure (i.e. Block) produced the highest level of saliency in attracting eye movements (Experiment 3). Overall, the results show that saccades are planned on the representation of the whole target shape rather than a local salient region based on orientation contrast cues, and that the various texture profiles were important only to the extent that they affected the time to programme a saccade.
    Matched MeSH terms: Eye Movements*
  2. Fulltext Feature selection and classifier parameters estimation for EEG signals peak detection using particle swarm optimization
    Adam A, Shapiai MI, Tumari MZ, Mohamad MS, Mubin M
    ScientificWorldJournal, 2014;2014:973063.
    PMID: 25243236 DOI: 10.1155/2014/973063
    Electroencephalogram (EEG) signal peak detection is widely used in clinical applications. The peak point can be detected using several approaches, including time, frequency, time-frequency, and nonlinear domains depending on various peak features from several models. However, there is no study that provides the importance of every peak feature in contributing to a good and generalized model. In this study, feature selection and classifier parameters estimation based on particle swarm optimization (PSO) are proposed as a framework for peak detection on EEG signals in time domain analysis. Two versions of PSO are used in the study: (1) standard PSO and (2) random asynchronous particle swarm optimization (RA-PSO). The proposed framework tries to find the best combination of all the available features that offers good peak detection and a high classification rate from the results in the conducted experiments. The evaluation results indicate that the accuracy of the peak detection can be improved up to 99.90% and 98.59% for training and testing, respectively, as compared to the framework without feature selection adaptation. Additionally, the proposed framework based on RA-PSO offers a better and reliable classification rate as compared to standard PSO as it produces low variance model.
    Matched MeSH terms: Eye Movements/physiology*
  3. Fulltext Relationship between autonomic arousal and attention orienting in children and adolescents with ADHD, autism and co-occurring ADHD and autism
    Bellato A, Arora I, Kochhar P, Ropar D, Hollis C, Groom MJ
    Cortex, 2023 Sep;166:306-321.
    PMID: 37459680 DOI: 10.1016/j.cortex.2023.06.002
    INTRODUCTION: Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) may be characterized by different profiles of visual attention orienting. However, there are also many inconsistent findings emerging from the literature, probably due to the fact that the potential effect of autonomic arousal (which has been proposed to be dysregulated in these conditions) on oculomotor performance has not been investigated before. Moreover, it is not known how visual attention orienting is affected by the co-occurrence of ADHD and autism in people with a double diagnosis.

    METHODS: 99 children/adolescents with or without ADHD and/or autism (age 10.79 ± 2.05 years, 65% boys) completed an adapted version of the gap-overlap task (with baseline and overlap trials only). The social salience and modality of stimuli were manipulated between trials. Eye movements and pupil size were recorded. We compared saccadic reaction times (SRTs) between diagnostic groups and investigated if a trial-by-trial association existed between pre-saccadic pupil size and SRTs.

    RESULTS: Faster orienting (shorter SRT) was found for baseline compared to overlap trials, faces compared to non-face stimuli and-more evidently in children without ADHD and/or autism-for multi-modal compared to uni-modal stimuli. We also found a linear negative association between pre-saccadic pupil size and SRTs, in autistic participants (without ADHD), and a quadratic association in children with ADHD (without autism), for which SRTs were slower when intra-individual pre-saccadic pupil size was smallest or largest.

    CONCLUSION: Our findings are in line with previous literature and indicate a possible effect of dysregulated autonomic arousal on oculomotor mechanisms in autism and ADHD, which should be further investigated in future research studies with larger samples, to reliably investigate possible differences between children with single and dual diagnoses.

    Matched MeSH terms: Eye Movements
  4. Fulltext A simple model to demonstrate the movements and the axes of the eyeball
    Nayak S, Soumya KV
    Adv Physiol Educ, 2009 Dec;33(4):356-7.
    PMID: 19948688 DOI: 10.1152/advan.00047.2009
    Matched MeSH terms: Eye Movements/physiology*
  5. The inter-relationship between magnification, field of view and contrast reserve: the effect on reading performance
    Mohammed Z, Dickinson CM
    Ophthalmic Physiol Opt, 2000 Nov;20(6):464-72.
    PMID: 11127126 DOI: 10.1111/j.1475-1313.2000.tb01124.x
    For the reading task, contrast reserve is defined as the ratio of the letter contrast of the printed letters, to the reader's contrast threshold. Acuity reserve is the ratio of the print size used for the reading task, to the reader's visual acuity. The effects of low contrast reserve on reading performance were investigated at various magnifications, ranging from 3x to 7.5x, with the field of view systematically controlled. Eye movements were recorded whilst normally sighted subjects read using the magnifiers. It was shown that with adequate contrast reserve, increasing the field of view improved the reading rate because of the resulting increase in forward saccade length. Conversely, reducing the contrast reserve slowed the reading rate by decreasing the length of forward saccades and increasing the mean fixation duration, suggesting that the perceptual span is reduced at low contrast reserve. This study also shows that when the contrast reserve is low, providing magnification higher than that required for letter recognition (that is, increasing the acuity reserve) will not improve the reading performance. Furthermore, even when the contrast reserve was high, reading rates were lower for the magnifications of 5x and higher, because increases in saccade length do not match those of the retinal image size at these magnifications.
    Matched MeSH terms: Eye Movements/physiology
  6. Fulltext Eye tracker as an implied social presence: awareness of being eye-tracked induces social-norm-based looking behaviour
    Wong HK, Stephen ID
    J Eye Mov Res, 2019 Aug 05;12(2).
    PMID: 33828723 DOI: 10.16910/jemr.12.2.5
    Human behaviour is not only influenced by the physical presence of others, but also implied social presence. This study examines the impact of awareness of being eye-tracked on eye movement behaviour in a laboratory setting. During a classic yes/no face recognition task, participants were made to believe that their eye movements were recorded (or not recorded) by eye trackers. Their looking patterns with and without the awareness of being eye-tracked were compared while perceiving social (faces, faces-and-bodies) and non-social (inanimate objects) video stimuli. Area-of-interest (AOI) analysis revealed that misinformed participants (who were not aware that their eye movements were being recorded) looked more at the body (chest and waist) compared to informed participants (who believed they were being eye-tracked), whereas informed participants fixated longer on the mouth and shorter on the eyes of female models than misinformed participants did. These findings highlight the potential impact of an awareness of being eye tracked on one's eye movement pattern when perceiving a social stimulus. We conclude that even within laboratory settings an eye tracker may function as an implied social presence that leads individuals to modify their eye movement behaviour according to socially-derived inhibitory norms.
    Matched MeSH terms: Eye Movements
  7. Looking at remembering: Eye movements, pupil size, and autobiographical memory
    Janssen SMJ, Foo A, Johnson SN, Lim A, Satel J
    Conscious Cogn, 2021 03;89:103089.
    PMID: 33607423 DOI: 10.1016/j.concog.2021.103089
    To examine the relationship between visual imagery and autobiographical memory, eye position and pupil size were recorded while participants first searched for memories and then reconstructed the retrieved memories (Experiment 1), or only searched for memories (Experiment 2). In Experiment 1, we observed that, although recollective experience was not associated with the number of fixations per minute, memories that took longer to retrieve were linked to increased pupil size. In Experiment 2, we observed that directly retrieved memories were recalled more quickly and were accompanied by smaller pupils than generatively retrieved memories. After correcting for response time, retrieval mode also produced an effect, showing that decreased pupil size is not simply due to directly retrieved memories being recalled more quickly. These findings provide compelling evidence that objective measures, such as pupil size, can be used alongside subjective measures, such as self-reports, to distinguish between directly retrieved and generatively retrieved memories.
    Matched MeSH terms: Eye Movements
  8. The impact of cognitive load on reward evaluation
    Krigolson OE, Hassall CD, Satel J, Klein RM
    Brain Res, 2015 Nov 19;1627:225-32.
    PMID: 26431993 DOI: 10.1016/j.brainres.2015.09.028
    The neural systems that afford our ability to evaluate rewards and punishments are impacted by a variety of external factors. Here, we demonstrate that increased cognitive load reduces the functional efficacy of a reward processing system within the human medial-frontal cortex. In our paradigm, two groups of participants used performance feedback to estimate the exact duration of one second while electroencephalographic (EEG) data was recorded. Prior to performing the time estimation task, both groups were instructed to keep their eyes still and avoid blinking in line with well established EEG protocol. However, during performance of the time-estimation task, one of the two groups was provided with trial-to-trial-feedback about their performance on the time-estimation task and their eye movements to induce a higher level of cognitive load relative to participants in the other group who were solely provided with feedback about the accuracy of their temporal estimates. In line with previous work, we found that the higher level of cognitive load reduced the amplitude of the feedback-related negativity, a component of the human event-related brain potential associated with reward evaluation within the medial-frontal cortex. Importantly, our results provide further support that increased cognitive load reduces the functional efficacy of a neural system associated with reward processing.
    Matched MeSH terms: Eye Movements
  9. Eye movements of recent and remote autobiographical memories: fewer and longer lasting fixations during the retrieval of childhood memories
    El Haj M, Boutoleau-Bretonnière C, Janssen SMJ
    Psychol Res, 2021 Sep;85(6):2466-2473.
    PMID: 32862309 DOI: 10.1007/s00426-020-01403-3
    There is an increased interest in the study of eye movements during the retrieval of autobiographical memories. Following this trend, the aim of the current study was to evaluate eye movements during the retrieval of remote and recent autobiographical memories. We instructed 71 participants to retrieve memories of personal events from early childhood (6-10 years), late childhood/early adolescence (11-14 years), late adolescence (15-18 years), and the last month. During the retrieval of these memories, participants wore eye-tracking glasses. Analyses showed that early childhood memories triggered fewer fixations and fixations with longer durations than memories from the last month. However, no significant differences were observed for the number of saccades, saccade durations, or total amplitude of the saccades. The fewer and longer lasting fixations during the retrieval of early childhood memories can be attributed either to the visual system reconstructing remote memories from an observer perspective or to difficulties when reconstructing remote memories.
    Matched MeSH terms: Eye Movements
  10. The prioritization of visuo-spatial associations during mental imagery
    Umar H, Mast FW, Cacchione T, Martarelli CS
    Cogn Process, 2021 May;22(2):227-237.
    PMID: 33404898 DOI: 10.1007/s10339-020-01010-5
    While previous research has shown that during mental imagery participants look back to areas visited during encoding it is unclear what happens when information presented during encoding is incongruent. To investigate this research question, we presented 30 participants with incongruent audio-visual associations (e.g. the image of a car paired with the sound of a cat) and later asked them to create a congruent mental representation based on the auditory cue (e.g. to create a mental representation of a cat while hearing the sound of a cat). The results revealed that participants spent more time in the areas where they previously saw the object and that incongruent audio-visual information during encoding did not appear to interfere with the generation and maintenance of mental images. This finding suggests that eye movements can be flexibly employed during mental imagery depending on the demands of the task.
    Matched MeSH terms: Eye Movements
  11. Fulltext Bilateral idiopathic optic perineuritis in a young Malay woman: A case report
    Ayesha Mohd Zain, Umi Kalthum Md Noh, Mushawiahti Mustapha, Norshamsiah Md. Din, Bastion, Mae Lynn Catherine
    Neurology Asia, 2015;20(4):407-409.
    MyJurnal
    A 28-year-old Malay woman presented with severe loss of vision in both eyes associated with periocular pain on eye movement. She was completely blind at presentation and examination showed optic discs
    swelling. Optic nerve imaging showed ‘doughnut sign’, characteristic of optic perineuritis. Steroid was
    given over six months. Visual function improved gradually and was maintained at one year follow-up.
    This case highlights the importance of differentiation between optic neuritis and optic perineuritis as
    visual recovery depends on prolonged management with corticosteroid in optic perineuritis.
    Matched MeSH terms: Eye Movements
  12. Using other minds as a window onto the world: guessing what happened from clues in behaviour
    Pillai D, Sheppard E, Ropar D, Marsh L, Pearson A, Mitchell P
    J Autism Dev Disord, 2014 Oct;44(10):2430-9.
    PMID: 24710812 DOI: 10.1007/s10803-014-2106-x
    It has been proposed that mentalising involves retrodicting as well as predicting behaviour, by inferring previous mental states of a target. This study investigated whether retrodiction is impaired in individuals with autism spectrum disorders (ASD). Participants watched videos of real people reacting to the researcher behaving in one of four possible ways. Their task was to decide which of these four "scenarios" each person responded to. Participants' eye movements were recorded. Participants with ASD were poorer than comparison participants at identifying the scenario to which people in the videos were responding. There were no group differences in time spent looking at the eyes or mouth. The findings imply those with ASD are impaired in using mentalising skills for retrodiction.
    Matched MeSH terms: Eye Movements/physiology
  13. Fulltext Can people guess what happened to others from their reactions?
    Pillai D, Sheppard E, Mitchell P
    PLoS One, 2012;7(11):e49859.
    PMID: 23226227 DOI: 10.1371/journal.pone.0049859
    Are we able to infer what happened to a person from a brief sample of his/her behaviour? It has been proposed that mentalising skills can be used to retrodict as well as predict behaviour, that is, to determine what mental states of a target have already occurred. The current study aimed to develop a paradigm to explore these processes, which takes into account the intricacies of real-life situations in which reasoning about mental states, as embodied in behaviour, may be utilised. A novel task was devised which involved observing subtle and naturalistic reactions of others in order to determine the event that had previously taken place. Thirty-five participants viewed videos of real individuals reacting to the researcher behaving in one of four possible ways, and were asked to judge which of the four 'scenarios' they thought the individual was responding to. Their eye movements were recorded to establish the visual strategies used. Participants were able to deduce successfully from a small sample of behaviour which scenario had previously occurred. Surprisingly, looking at the eye region was associated with poorer identification of the scenarios, and eye movement strategy varied depending on the event experienced by the person in the video. This suggests people flexibly deploy their attention using a retrodictive mindreading process to infer events.
    Matched MeSH terms: Eye Movements/physiology
  14. Stimulus-response incompatibility eliminates inhibitory cueing effects with saccadic but not manual responses
    Eng V, Lim A, Kwon S, Gan SR, Jamaluddin SA, Janssen SMJ, et al.
    Atten Percept Psychophys, 2017 May;79(4):1097-1106.
    PMID: 28229429 DOI: 10.3758/s13414-017-1295-8
    There are thought to be two forms of inhibition of return (IOR) depending on whether the oculomotor system is activated or suppressed. When saccades are allowed, output-based IOR is generated, whereas input-based IOR arises when saccades are prohibited. In a series of 4 experiments, we mixed or blocked compatible and incompatible trials with saccadic or manual responses to investigate whether cueing effects would follow the same pattern as those observed with more traditional peripheral onsets and central arrows. In all experiments, an uninformative cue was displayed, followed by a cue-back stimulus that was either red or green, indicating whether a compatible or incompatible response was required. The results showed that IOR was indeed observed for compatible responses in all tasks, whereas IOR was eliminated for incompatible trials-but only with saccadic responses. These findings indicate that the dissociation between input- and output-based forms of IOR depends on more than just oculomotor activation, providing further support for the existence of an inhibitory cueing effect that is distinct to the manual response modality.
    Matched MeSH terms: Eye Movements/physiology
  15. Ocular myasthenia gravis and idiopathic orbital inflammatory disease: double the trouble!
    Sharudin SN, Govindasamy G, Mohamad NF, Kanesalingam R, Vasudevan SK
    Can J Ophthalmol, 2018 04;53(2):e55-e58.
    PMID: 29631841 DOI: 10.1016/j.jcjo.2017.07.024
    Matched MeSH terms: Eye Movements/physiology*
  16. Fulltext Does the implicit models of leadership influence the scanning of other-race faces in adults?
    Densten IL, Borrowman L
    PLoS One, 2017;12(7):e0179058.
    PMID: 28686605 DOI: 10.1371/journal.pone.0179058
    The current study aims to identify the relationships between implicit leadership theoretical (ILT) prototypes / anti-prototype and five facial features (i.e., nasion, upper nose, lower nose, and upper lip) of a leader from a different race than respondents. A sample of 81 Asian respondents viewed a 30-second video of a Caucasian female who in a non-engaging manner talked about her career achievements. As participants watch the video, their eye movements were recorded via an eye tracking devise. While previous research has identified that ILT influences perceptional and attitudinal ratings of leaders, the current study extends these findings by confirming the impact of ILT on the gaze patterns of other race participants, who appear to adopt system one type thinking. This study advances our understanding in how cognitive categories or schemas influence the physicality of individuals (i.e., eye gaze or movements). Finally, this study confirms that individual ILT factors have a relationship with the eye movements of participants and suggests future research directions.
    Matched MeSH terms: Eye Movements/physiology
  17. Time course of inhibition of return in a spatial cueing paradigm with distractors
    Eng V, Lim A, Janssen SMJ, Satel J
    Acta Psychol (Amst), 2018 Feb;183:51-57.
    PMID: 29328938 DOI: 10.1016/j.actpsy.2017.12.011
    Studies of endogenous and exogenous attentional orienting in spatial cueing paradigms have been used to investigate inhibition of return, a behavioral phenomenon characterized by delayed reaction time in response to recently attended locations. When eye movements are suppressed, attention is covertly oriented to central or peripheral stimuli. Overt orienting, on the other hand, requires explicit eye movements to the stimuli. The present study examined the time course of slowed reaction times to previously attended locations when distractors are introduced into overt and covert orienting tasks. In a series of experiments, manual responses were required to targets following central and peripheral cues at three different cue-target intervals, with and without activated oculomotor systems. The results demonstrate that, when eye movements are suppressed, behavioral inhibition is reduced or delayed in magnitude by the presence of a distractor relative to conditions without distractors. However, the time course of behavioral inhibition when eye movements are required remains similar with or without distractors.
    Matched MeSH terms: Eye Movements/physiology
  18. Fulltext In search of a reliable electrophysiological marker of oculomotor inhibition of return
    Satel J, Hilchey MD, Wang Z, Reiss CS, Klein RM
    Psychophysiology, 2014 Oct;51(10):1037-45.
    PMID: 24976355 DOI: 10.1111/psyp.12245
    Inhibition of return (IOR) operationalizes a behavioral phenomenon characterized by slower responding to cued, relative to uncued, targets. Two independent forms of IOR have been theorized: input-based IOR occurs when the oculomotor system is quiescent, while output-based IOR occurs when the oculomotor system is engaged. EEG studies forbidding eye movements have demonstrated that reductions of target-elicited P1 components are correlated with IOR magnitude, but when eye movements occur, P1 effects bear no relationship to behavior. We expand on this work by adapting the cueing paradigm and recording event-related potentials: IOR is caused by oculomotor responses to central arrows or peripheral onsets and measured by key presses to peripheral targets. Behavioral IOR is observed in both conditions, but P1 reductions are absent in the central arrow condition. By contrast, arrow and peripheral cues enhance Nd, especially over contralateral electrode sites.
    Matched MeSH terms: Eye Movements/physiology*
  19. Exploring bedside clinical features of parkinsonism: A focus on differential diagnosis
    Bhidayasiri R, Rattanachaisit W, Phokaewvarangkul O, Lim TT, Fernandez HH
    Parkinsonism Relat Disord, 2019 Feb;59:74-81.
    PMID: 30502095 DOI: 10.1016/j.parkreldis.2018.11.005
    The proper diagnosis of parkinsonian disorders usually involves three steps: identifying core features of parkinsonism; excluding other causes; and collating supportive evidence based on clinical signs or investigations. While the recognition of cardinal parkinsonian features is usually straightforward, the appreciation of clinical features suggestive of specific parkinsonian disorders can be challenging, and often requires greater experience and skills. In this review, we outline the clinical features that are relevant to the differential diagnosis of common neurodegenerative parkinsonian disorders, including Parkinson's disease, multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration. We aim to make this process relatable to clinicians-in-practice, therefore, have categorised the list of clinical features into groups according to the typical sequence on how clinicians would elicit them during the examination, starting with observation of facial expression and clinical signs of the face, spotting eye movement abnormalities, examination of tremors and jerky limb movements, and finally, examination of posture and gait dysfunction. This review is not intended to be comprehensive. Rather, we have focused on the most common clinical signs that are potentially key to making the correct diagnosis and those that do not require special skills or training for interpretation. Evidence is also provided, where available, such as diagnostic criteria, consensus statements, clinicopathological studies or large multi-centre registries. Pitfalls are also discussed when relevant to the diagnosis. While no clinical signs are pathognomonic for certain parkinsonian disorders, certain clinical clues may assist in narrowing a differential diagnosis and tailoring focused investigations for the individual patient.
    Matched MeSH terms: Eye Movements
  20. Fulltext Case report: progression of pre-septal cellulitis to orbital subperiosteal abscess despite intravenous broad-spectrum antibiotics in a child
    Noor Aniah A, Norshamsiah MD, Safinaz MK, Bastion, MLC, Mawaddah A
    Journal of Surgical Academia, 2016;6(1):62-65.
    MyJurnal
    We report a case of a 7-year-old girl who initially presented with painless right eyelid swelling with full extra-ocular movement (EOM). She was treated with intravenous broad-spectrum antibiotics for preseptal cellulitis but her condition worsened. An urgent magnetic resonance imaging (MRI) of the brain and orbit showed orbital abscess, subperiosteal abscess in the medial orbital wall and evidence of sinusitis in the anterior ethmoidal air cells. She underwent Endoscopic Orbital Decompression (EOD) surgery on day 4 of presentation and her condition improved remarkably. We report a case of orbital abscess with subperiosteal abscess in the medial orbital wall. This case highlights the possibility of progression of orbital cellulitis despite administration of a broad-spectrum antibiotic.
    Matched MeSH terms: Eye Movements
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