Oculomotor and inhibitory control in dyslexia

Previous research has suggested that people with dyslexia may have an impairment of inhibitory control. The oculomotor system is vulnerable to interference at various levels of the system, from high level cognitive control to peripheral neural pathways. Therefore, in this work we examined two forms of oculomotor inhibition and two forms of oculomotor interference at high and low levels of the control system. This study employed a prosaccade, antisaccade, and a recent distractor eye movement task (akin to a spatial negative priming) in order to explore high level cognitive control and the inhibition of a competing distractor. To explore low-level control we examined the frequency of microsaccades and post-saccade oscillations. The findings demonstrated that dyslexics have an impairment of volitional inhibitory control, reflected in the antisaccade task. In contrast, inhibitory control at the location of a competing distractor was equivalent in the dyslexic and non-dyslexic groups. There was no difference in the frequency of microsaccades between the two groups. However, the dyslexic group generated larger microsaccades prior to the target onset in the prosaccade and the antisaccade tasks.The groups did not differ in the frequency or in the morphology of the post-saccade oscillations. These findings reveal that the word reading and attentional difficulties of dyslexic readers cannot be attributed to an impairment in the inhibition of a visual distractor or interference from low-level oculomotor instability. We propose that the inhibitory impairment in dyslexia occurs at a higher cognitive level, perhaps in relation to the process of attentional disengagement

Likelihood of substance abuse for dyslexics may be influenced by socioeconomic background and metacognition

Research into the relationship between dyslexia and substance abuse has led to inconsistent findings. Some research papers suggest that dyslexics are at increased risk of substance abuse (and related) problems, whilst some research would suggest the contrary. We suggest that these different observations can be accounted for by socioeconomic background and the effect of this on metacognition. There are also an increased number of other factors which may predominantly affect people from low socioeconomic backgrounds which could exacerbate substance abuse

Does sleep affect alcohol-related attention bias?

Background: Poor quality sleep can lead to executive function deficits, including problems with inhibitory control. Similarly, substance use is associated with decreased inhibitory control for substance-related stimuli. Therefore, this study investigated whether sleep quality is associated with attentional bias. Methods: Participants were 39 university students (18-28 years, 29 females). An eye tracking task was used to measure attentional bias for alcohol-related stimuli. Alcohol usage and sleep quality were measured using self- report questionnaires (AUDIT and PSQI respectively). Results: An attentional bias related to alcohol usage was observed within the participants. However, there was no association observed with sleep quality. Conclusion: Therefore, we conclude that sleep quality may not influence attentional biases

A comparison of post-saccadic oscillations in European-Born and China-Born British University Undergraduates

Previous research has revealed that people from different genetic, racial, biological, and/or cultural backgrounds may display fundamental differences in eye-tracking behavior. These differences may have a cognitive origin or they may be at a lower level within the neurophysiology of the oculomotor network, or they may be related to environment factors. In this paper we investigated one of the physiological aspects of eye movements known as post-saccadic oscillations and we show that this type of eye movement is very different between two different populations. We compared the post-saccadic oscillations recorded by a video-based eye tracker between two groups of participants: European-born and Chinese-born British students. We recorded eye movements from a group of 42 Caucasians defined as White British or White Europeans and 52 Chinese-born participants all with ages ranging from 18 to 36 during a prosaccade task. The post-saccadic oscillations were extracted from the gaze data which was compared between the two groups in terms of their first overshoot and undershoot. The results revealed that the shape of the post-saccadic oscillations varied significantly between the two groups which may indicate a difference in a multitude of genetic, cultural, physiologic, anatomical or environmental factors. We further show that the differences in the post-saccadic oscillations could influence the oculomotor characteristics such as saccade duration. We conclude that genetic, racial, biological, and/or cultural differences can affect the morphology of the eye movement data recorded and should be considered when studying eye movements and oculomotor fixation and saccadic behaviors

The influence of organic and conventional fertilisation and crop protection practices, preceding crop, harvest year and weather conditions on yield and quality of potato (Solanum tuberosum) in a long-term management trial

The effects of organic versus conventional crop management practices (fertilisation, crop protection) and preceding crop on potato tuber yield (total, marketable, tuber size grade distribution) and quality (proportion of diseased, green and damaged tubers, tuber macro-nutrient concentrations) parameters were investigated over six years (2004–2009) as part of a long-term factorial field trial in North East England. Inter-year variability (the effects of weather and preceding crop) was observed to have a profound effect on yields and quality parameters, and this variability was greater in organic fertility systems. Total and marketable yields were significantly reduced by the use of both organic crop protection and fertility management. However, the yield gap between organic and conventional fertilisation regimes was greater and more variable than that between crop protection practices. This appears to be attributable mainly to lower and less predictable nitrogen supply in organically fertilised crops. Increased incidence of late blight in organic crop protection systems only occurred when conventional fertilisation was applied. In organically fertilised crops yield was significantly higher following grass/red clover leys than winter wheat, but there was no pre-crop effect in conventionally fertilised crops. The results highlight that nitrogen supply from organic fertilisers rather than inefficient pest and disease control may be the major limiting factor for yields in organic potato production systems

Evidence for different thermal ecotypes in range centre and trailing edge kelp populations

Determining and predicting species’ responses to climate change is a fundamental goal of contemporary ecology. When interpreting responses to warming species are often treated as a single physiological unit with a single species-wide thermal niche. This assumes that trailing edge populations are most vulnerable to warming, as it is here where a species’ thermal niche will be exceeded first. Local adaptation can, however, result in narrower thermal tolerance limits for local populations, so that similar relative increases in temperature can exceed local niches throughout a species range. We used a combination of common garden temperature heat-shock experiments (8–32 °C) and population genetics (microsatellites) to identify thermal ecotypes of northeast Atlantic range centre and trailing edge populations of the habitat-forming kelp, Laminaria digitata. Using upregulation of hsp70 as an indicator of thermal stress, we found that trailing edge populations were better equipped to tolerate acute temperature shocks. This pattern was consistent across seasons, indicating that between-population variability is fixed. High genetic structuring was also observed, with range centre and trailing edge populations representing highly distinct clusters with little gene flow between regions. Taken together, this suggests the presence of distinct thermal ecotypes for L. digitata, which may mean responses to future warming are more complex than linear range contractions. © 2019 Elsevier B.V

Inadvertent paralog inclusion drives artifactual topologies and timetree estimates in phylogenomics

Increasingly, large phylogenomic datasets include transcriptomic data from non-model organisms. This has allowed controversial and unexplored evolutionary relationships in the tree of life to be addressed but also increases the risk of inadvertent inclusion of paralogs in the analysis. While this may be expected to result in decreased phylogenetic support it is not clear if it could also drive highly supported artefactual relationships. Many groups, including the hyper-diverse Lissamphibia, are especially susceptible to these issues due to ancient gene duplication events, small numbers of sequenced genomes and because transcriptomes are increasingly applied to resolve historically conflicting taxonomic hypotheses. We tested the potential impact of paralog inclusion on the topologies and timetree estimates of the Lissamphibia using published and de novo sequencing data including 18 amphibian species, from which 2,656 single-copy gene families were identified. A novel paralog filtering approach resulted in four differently curated datasets, which were used for phylogenetic reconstructions using Bayesian inference, maximum likelihood and quartet-based supertrees. We found that paralogs drive strongly supported conflicting hypotheses within the Lissamphibia (Batrachia and Procera) and older divergence time estimates even within groups where no variation in topology was observed. All investigated methods, except Bayesian inference with the CAT-GTR model, were found to be sensitive to paralogs, but with filtering convergence to the same answer (Batrachia) was observed. This is the first large-scale study to address the impact of orthology selection using transcriptomic data and emphasises the importance of quality over quantity particularly for understanding relationships of poorly sampled taxa

Effect of aging on post-saccadic oscillations

Recent research have shown that the eye movement data measured by an eye tracker does not necessarily reflect the exact rotations of the eyeball. For example, post-saccadic eye movements may be more reflecting the relative movements between the pupil and the iris rather than the eyeball oscillations. Since, accurate measurement of eye movements is important in many studies, it is crucial to identify different factors that influence the dynamics of the eye movements measured by an eye tracker. Previous studies have shown that deformation of the internal structure of the iris and size of the pupil directly affect the amplitude of the post-saccadic oscillations that are measured by video-based eye trackers that are pupil-based. In this paper, we look at the effect of aging on post-saccadic oscillations. We recorded eye movements from a group of 43 young and 22 older participants during an abstract and a more natural viewing task. The recording was conducted with a video-based eye tracker using the pupil center and corneal reflection. We anticipated that changes in the muscle strength as an effect of aging might affect, directly or indirectly, the post-saccadic oscillations. Results showed that the size of the post-saccadic oscillations were significantly larger for our older group. The results suggests that aging has to be considered as an important factor when studying the post-saccadic eye movements

Dyslexia and substance use in a University Undergraduate Population

Background: A number of cognitive deficits are associated with dyslexia. However, only a limited amount of research has been performed exploring a putative link between dyslexia and substance use. As substance use is thought to involve a cognitive component, it is possible that the pattern of substance use would be different for dyslexic participants, when compared to nondyslexic controls. During the current study, a guiding hypothesis was that people with dyslexia would demonstrate less substance use than nondyslexic controls. Theories of memory activation, automaticity, and attentional bias in substance use suggest that cognitive components of substance use are important in the development and maintenance of continued substance use and it is thought that, at least some of these components, would be impaired in a dyslexic population. Objectives: If the cognitive deficits displayed by dyslexics somehow impair the development of cognitive components of substance use, substance use for dyslexic participants may be less pronounced. This paper therefore examines this hypothesis by comparing substance use within dyslexic and nondyslexic participants, from an undergraduate population. Methods: This was an exploratory questionnaire-based study. Dyslexic participants (n = 35) were compared to control participants (n = 62) on a series of questions designed to measure their substance use history. Results: The results provided preliminary evidence of a difference between dyslexic and nondyslexic substance use. Dyslexics reported a substance use history that was significantly lower than nondyslexic controls. Conclusions/Importance: These results are interpreted in terms of cognitive deficits within dyslexia and with reference to the cognitive model of substance use