The concurrent programming of saccades

Sequences of saccades have been shown to be prepared concurrently however it remains unclear exactly what aspects of those saccades are programmed in parallel. To examine this participants were asked to make one or two target-driven saccades: a reflexive saccade; a voluntary saccade; a reflexive then a voluntary saccade; or vice versa. During the first response the position of a second target was manipulated. The new location of the second saccade target was found to impact on second saccade latencies and second saccade accuracy showing that some aspects of the second saccade program are prepared in parallel with the first. However, differences were found in the specific pattern of effects for each sequence type. These differences fit well within a general framework for saccade control in which a common priority map for saccade control is computed and the influence of saccade programs on one another depends not so much on the types of saccade being produced but rather on the rate at which their programs develop

The programming of sequences of saccades

Saccadic eye movements move the high-resolution fovea to point at regions of interest. Saccades can only be generated serially (i.e., one at a time). However, what remains unclear is the extent to which saccades are programmed in parallel (i.e., a series of such moments can be planned together) and how far ahead such planning occurs. In the current experiment, we investigate this issue with a saccade contingent preview paradigm. Participants were asked to execute saccadic eye movements in response to seven small circles presented on a screen. The extent to which participants were given prior information about target locations was varied on a trial-by-trial basis: participants were aware of the location of the next target only, the next three, five, or all seven targets. The addition of new targets to the display was made during the saccade to the next target in the sequence. The overall time taken to complete the sequence was decreased as more targets were available up to all seven targets. This was a result of a reduction in the number of saccades being executed and a reduction in their saccade latencies. Surprisingly, these results suggest that, when faced with a demand to saccade to a large number of target locations, saccade preparation about all target locations is carried out in paralle

Using endogenous saccades to characterize fatigue in multiple sclerosis

Purpose Multiple Sclerosis (MS) is likely to cause dysfunction of neural circuits between brain regions increasing brain working load or a subjective overestimation of such working load leading to fatigue symptoms. The aim of this study was to investigate if saccades can reveal the effect of fatigue in patients with MS. Methods Patients diagnosed with MS (EDSS<=3) and age matched controls were recruited. Eye movements were monitored using an infrared eyetracker. Each participant performed 40 trials in an endogenous generated saccade paradigm (valid and invalid trials). The fatigue severity scale (FSS) was used to assess the severity of fatigue. FSS scores were used to define two subgroups, the MS fatigue group (score above normal range) and the MS non-fatigue. Differences between groups were tested using linear mixed models. Results Thirty-one MS patients and equal number of controls participated in this study. FSS scores were above the normal range in 11 patients. Differences in saccade latency were found according to group (p<0.001) and trial validity (p=0.023). Differences were 16.9 ms, between MS fatigue and MS non-fatigue, 15.5 ms between MS fatigue and control. The mean difference between valid and invalid trials was 7.5 ms. Differences in saccade peak velocity were found according to group (p<0.001), the difference between MS fatigue and control was 22.3°/s and between MS fatigue and non-fatigue was 12.3°/s. Group was a statistically significant predictor for amplitude (p<0.001). FSS scores were correlated with peak velocity (p=0.028) and amplitude (p=0.019). Conclusion Consistent with the initial hypothesis, our study revealed altered saccade latency, peak velocity and amplitude in patients with fatigue symptoms. Eye movement testing can complement the standard inventories when investigating fatigue because they do not share similar limitations. Our findings contribute to the understanding of functional changes induced by MS and might be useful for clinical trials and treatment decisions.We would like to acknowledge that part of this work has been presented at 3rd International Porto Congress of Multiple Sclerosis, February 27–28, 2015, Porto, Portugal and ECEM 2015 | XVIII. European Conference on Eye Movements, August 16–21, 2015, Viena, Austria. We thank the Multiple Sclerosis Association “Todos com a Esclerose Multiple (TEM)” and the Clinical and Academic Centre (CAA-Hospital de Braga) for their support financial support and for providing facilities for data collection, respectively. We also acknowledge: i) Carla Sofia for recruiting all the MS participants and most of the controls, ii) Two anonymous reviewers for their opinion about an early version of this manuscript and iii) Liz Pearce for proofreading the manuscript. Vision Rehabilitation Lab. receives founding from Shamir Portugal and from grant PTDC/DTP-EPI/0412/2012, Fundação para a Ciência e a Tecnologia, co-financiado pelo FEDER através do COMPETE.info:eu-repo/semantics/publishedVersio

Relationships between neuropsychological and antisaccade measures in multiple sclerosis patients

Background: The Stroop test is frequently used to assess deficits in inhibitory control in people with multiple sclerosis (MS). This test has limitations and antisaccade eye movements, that also measure inhibitory control, may be an alternative to Stroop.Objectives: The aim of this study was twofold: (i) to investigate if the performance in the antisaccade task is altered in patients with MS and (ii) to investigate the correlation between performances in neuropsychological tests, the Stroop test and the antisaccade task.Methods: We measured antisaccades (AS) parameters with an infrared eye tracker (SMIRED 250 Hz) using a standard AS paradigm. A total of 38 subjects diagnosed with MS and 38 age and gender matched controls participated in this study. Neuropsychological measures were obtained from the MS group.Results: Patients with MS have higher error rates and prolonged latency than controls in the antisaccade task. There was a consistent association between the Stroop performance and AS latency. Stroop performance but not AS latency was associated with other neuropsychological measures in which the MS group showed deficits.Conclusions: Our findings suggest that AS may be a selective and independent measure to investigate inhibitory control in patients with MS. More studies are necessary to confirm our results and to describe brain correlates associated with impaired performance in the antisaccade task in people diagnosed with MS.The Vision Rehabilitation Lab and Antonio Filipe Macedo receive or received funding from Shamir Optical Industry Lt, Portugal, from grants PTDC/DTP-EPI/0412/2012 (Prevalence and Costs of Visual Impairment in Portugal) and UID/FIS/04650/2013 (Framework of the Strategic Funding granted to Centre of Physics at Minho University). Multiple Sclerosis Association "Todos com a Esclerose Multiple" paid the salary of Marisa Borges Ferreira. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.info:eu-repo/semantics/publishedVersio

A first AFLP-based genetic linkage map for brine shrimp Artemia franciscana and its application in mapping the sex locus

We report on the construction of sex-specific linkage maps, the identification of sex-linked markers and the genome size estimation for the brine shrimp Artemia franciscana. Overall, from the analysis of 433 AFLP markers segregating in a 112 full-sib family we identified 21 male and 22 female linkage groups (2n = 42), covering 1,041 and 1,313 cM respectively. Fifteen putatively homologous linkage groups, including the sex linkage groups, were identified between the female and male linkage map. Eight sex-linked AFLP marker alleles were inherited from the female parent, supporting the hypothesis of a WZ-ZZ sex-determining system. The haploid Artemia genome size was estimated to 0.93 Gb by flow cytometry. The produced Artemia linkage maps provide the basis for further fine mapping and exploring of the sex-determining region and are a possible marker resource for mapping genomic loci underlying phenotypic differences among Artemia species

Keeping distance or getting closer : How others' emotions shape approach-avoidance postural behaviors and preferred interpersonal distance

Understanding the influence of emotions on social interactions is important for a global understanding of the dynamics of human behavior. In this study, we investigated the interplay between emotions, spontaneous approach or avoidance tendencies, and the regulation of interpersonal distance. Fifty-seven healthy adults participated in a three-part experiment involving exposure to approaching or withdrawing emotional faces (neutral, happy, sad, fearful, disgusted, angry). The sequence began with an initial computerized stop-distance task, followed by a postural task in which participants' approach or avoidance tendencies were quantified via center of pressure (CoP-Y) displacements on a force platform, and concluded with a final computerized stop-distance task. Our findings revealed a gradient in postural responses, with the most forward CoP-Y displacements for neutral and happy faces, indicative of approach tendencies. These were followed by lesser forward displacements for sad and fearful faces, and most pronounced backward displacements for disgusted and angry faces, indicating avoidance. Furthermore, we observed modulations in participants' preferred interpersonal distance based on emotional cues, with neutral and happy faces associated with shorter distances, and disgusted and angry faces linked to larger distances. Despite these similar results, no direct correlation was found between CoP-Y and preferred interpersonal distance, underscoring a dissociation between spontaneous and voluntary social behaviors. These results contribute to a better understanding of how emotional expressions shape social interactions and underscore the importance of considering emotional cues, postural action tendencies, and interpersonal distance in facilitating successful social interactions

Chapitre 5. Le codage de l’espace et des objets par la saccade oculaire

During visual exploration, the information about an object’s location must be transformed into motor commands through a series of operations known as sensorimotor transformations. In this chapter, we present a series of experiments that examines the frame of reference used for the preparation of double saccade sequences directed at one or two objects. We demonstrate that the action to be peformed on the object effects the coding of the second saccade. A second saccade directed at a new object is coded in a head-centred reference frame to aim for a target position on it and is adjusted to the landing position of the first saccade, whereas a second saccade within the same object is coded in an oculocentric reference frame as a fixed motor rector applied irrespective of the initial landing position on the object. The data may he included in a model that incorporates specfic eye control systems that depend on the selection of goal objects. Moreover, relative to the selection process, the saccadic plan is maintained either in a spatial memory – i.e. in the form of a target position to be aimed for – or in a motor memory – i. e. in the form of a movement to explore within the object

Between-object and within-object saccade programming in a visual search task

The role of the perceptual organization of the visual display on eye movement control was examined in two experiments using a task where a two-saccade sequence was directed toward either a single elongated object or three separate shorter objects. In the first experiment, we examined the consequences for the second saccade of a small displacement of the whole display during the first saccade. We found that between-object saccades compensated for the displacement to aim for a target position on the new object whereas within-object saccades did not show compensation but were coded as a fixed motor vector applied irrespective of wherever the preceding saccade landed. In the second experiment, we extended the paradigm to examine saccades performed in different directions. The results suggest that the within-object and between-object saccade distinction is an essential feature of saccadic planning

Biais perceptif et oculomoteur lors de la perception des visages (effets du vieillissement)

Résumé confidentielRésumé confidentielPARIS5-Bibliotheque electronique (751069902) / SudocSudocFranceF

Influence of eye dominance on oculomotor and attentional selection

International audienceThe dominant eye is the one used to perform a monocular task. There is an advantage of the hemifield controlateral to the dominant eye for both motor (higher saccade accuracy) and perceptual (faster detection) performance. The current study examines the influence of eye dominance in a dual-task paradigm. It involves a saccade and a discrimination task to one of the six locations possible, enabling the dissociation between saccade target and discrimination target. Four groups of participants are tested, according to their eye dominance and eye dominance strength. We investigate whether the higher saccade accuracy in the hemifield controlateral to the dominant eye is due to enhancement of the target location or to inhibition of the distractor locations. Preliminary results on discrimination performance suggest that eye dominance is associated to attentional asymmetries between visual hemifields