Motion processing deficits in migraine are related to contrast sensitivity

Background: There are conflicting reports concerning the ability of people with migraine to detect and discriminate visual motion. Previous studies used different displays and none adequately assessed other parameters that could affect performance, such as those that could indicate precortical dysfunction. Methods: Motion-direction detection, discrimination and relative motion thresholds were compared from participants with and without migraine. Potentially relevant visual covariates were included (contrast sensitivity; acuity; stereopsis; visual discomfort, stress, triggers; dyslexia). Results: For each task, migraine participants were less accurate than a control group and had impaired contrast sensitivity, greater visual discomfort, visual stress and visual triggers. Only contrast sensitivity correlated with performance on each motion task; it also mediated performance. Conclusions: Impaired performance on certain motion tasks can be attributed to impaired contrast sensitivity early in the visual system rather than a deficit in cortical motion processing per se. There were, however, additional differences for global and relative motion thresholds embedded in noise, suggesting changes in extrastriate cortex in migraine. Tasks to study the effects of noise on performance at different levels of the visual system and across modalities are recommended. A battery of standard visual tests should be included in any future work on the visual system and migraine

Dogs catch human yawns

This study is the first to demonstrate that human yawns are possibly contagious to domestic dogs (Canis familiaris). Twenty-nine dogs observed a human yawning or making control mouth movements. Twenty-one dogs yawned when they observed a human yawning, but control mouth movements did not elicit yawning from any of them. The presence of contagious yawning in dogs suggests that this phenomenon is not specific to primate species and may indicate that dogs possess the capacity for a rudimentary form of empathy. Since yawning is known to modulate the levels of arousal, yawn contagion may help coordinate dog–human interaction and communication. Understanding the mechanism as well as the function of contagious yawning between humans and dogs requires more detailed investigation

Tracking the migraine cycle using visual tasks

There are a number of reports that perceptual, electrophysiological and imaging measures can track migraine periodicity. As the electrophysiological and imaging research requires specialist equipment, it has few practical applications. This study sought to track changes in performance on four visual tasks over the migraine cycle. Coherence thresholds were measured for two motion and two orientation tasks. The first part of the study confirmed that the data obtained from an online study produced comparable results to those obtained under controlled laboratory conditions. Thirteen migraine with aura, 12 without aura, and 12 healthy controls participated. The second part of the study showed that thresholds for discriminating vertical coherent motion varied with the migraine cycle for a majority of the participants who tested themselves multiple times (four with aura, seven without). Performance improved two days prior to a migraine attack and remained improved for two days afterwards. This outcome is as expected from an extrapolation of earlier electrophysiological research. This research points to the possibility of developing sensitive visual tests that patients can use at home to predict an impending migraine attack and so take steps to try to abort it or, if it is inevitable, to plan their lives around it

Transient tritanopia in migraine: evidence for a large-field retinal abnormality in blue-yellow opponent pathways

purpose. To determine whether the magnitude of transient tritanopia (TT) differs between migraine and control groups. TT is a retinal phenomenon characterized by a paradoxical reduction in sensitivity to short-wavelength (purple) stimuli after extinction of long-wavelength (yellow) adapting displays. A group difference in the magnitude of TT would provide evidence for a retinal contribution to the S-cone–specific color-processing abnormalities that have been reported in migraine. methods. Thirty-two migraineurs and 32 age- and sex-matched control participants were tested with a four-alternative, forced-choice procedure to determine S-cone increment and decrement detection thresholds before and after adaptation to a long-wavelength (yellow) display and a neutral (white) display. Migraine history, migraine triggers, and pattern sensitivity were also assessed. results. Both groups’ detection thresholds for increment (purple) S-cone stimuli were increased after extinction of the long-wavelength adapting display compared with the neutral display, demonstrating TT. This loss of sensitivity was significantly greater in the migraine group. In contrast, loss of sensitivity to decrement (yellow) S-cone stimuli was less marked and did not differ between the groups. The magnitude of TT correlated positively with indices of pattern sensitivity and susceptibility to visually triggered migraines but not with migraine history. conclusions. These results demonstrate that abnormalities in a specific retinal circuit contribute to decreased short-wavelength sensitivity after adaptation in migraine. As thresholds did not correlate with indices of migraine history, it is unlikely that this finding reflects cumulative damage induced by repeated migraine episodes

Visual motion processing in migraine: enhanced motion after-effects are related to display contrast, visual symptoms, visual triggers and attack frequency

BACKGROUND: Visual after-effects are illusions that occur after prolonged viewing of visual displays. The motion after-effect (MAE), for example, is an illusory impression of motion after viewing moving displays: subsequently, stationary displays appear to drift in the opposite direction. After-effects have been used extensively in basic vision research and in clinical settings, and are enhanced in migraine. OBJECTIVES: To assess associations between (1) MAE duration and visual symptoms experienced during/between migraine/headache attacks, and (2) visual stimuli reported as migraine/headache triggers. METHODS: The MAE was elicited after viewing motion for 45 seconds. MAE duration was tested for three test contrast displays (high, medium, low). Participants also completed a headache questionnaire that included migraine/headache triggers. RESULTS: For each test contrast, the MAE was prolonged in migraine. MAE duration was associated with photophobia; visual triggers (flicker, striped patterns); and migraine or headache frequency. CONCLUSIONS: Group differences on various visual tasks have been attributed to abnormal cortical processing in migraine, such as hyperexcitability, heightened responsiveness and/or a lack of intra-cortical inhibition. The results are not consistent with hyperexcitability simply from a general lack of inhibition. Alternative multi-stage models are discussed and suggestions for further research are recommended, including visual tests in clinical assessments/clinical trials

Enhanced motion after-effects in migraine are related to contrast sensitivity: implications for models of differences in precortical/cortical function

Purpose: Visual tests can be used as non-invasive tools to test models of the pathophysiology underlying neurological conditions, such as migraine. For example, there are reports that the motion after-effect, which involves neural processing in several cortical areas, is prolonged in migraine. There are also reports of impaired contrast sensitivity in migraine, however, attributed to a precortical dysfunction. This study explored associations between these two tests of visual function. Specifically, it aimed to clarify whether the magnitude of the motion after-effect is affected by contrast and contrast sensitivity. Methods: The motion after-effect was elicited after observers viewed a coherently moving pattern for 45 seconds. The duration of the subsequent after-effect was measured with three different test display contrasts (high, medium, low). Contrast sensitivity was also assessed. Results: For each test display contrast, the motion after-effect was prolonged in migraine compared to the control group. Contrast sensitivity was poorer in the migraine group and was a significant predictor of motion after-effect duration. Conclusions: These results suggest an anomaly in early motion processing pathways in migraine that is likely linked with those pathways underlying contrast sensitivity. They provide further evidence for differences in visual processing that begin early, potentially starting at the retina, which have consequences for performance on tasks that putatively examine cortical processing. Differences in both precortical and cortical visual pathways are implicated in the pathophysiology underlying migraine

Sense about science - making sense of crime

Booklet 'Making Sense of Crime' published by registered charity 'Sense About Science'There’s always heated debate about crime in the media and a lot of political argument about how we should respond to it. But these arguments rarely provide insight into what actually causes crime, what lies behind trends over time and in different places, and how best to go about reducing it. Values inform how a society decides to deal with crime. We may decide that rehabilitation is a better principle than punishment, and this will influence how we decide what is most effective. However, we also expect these choices to be disciplined by sound evidence, because if crime policy ignores what works and what doesn’t, there are likely to be bad social consequences. And with over £10bn spent annually on tackling crime through the police, prisons, probation and courts, unless we look at evidence we can’t see how effective any of it is. Crime policy usually has twin aims – to prevent crime, and to seek justice by punishing those who commit offences. Research shows there’s only a loose link, if any, between the way offenders are punished and the number of offences committed. There is no reliable evidence for example, that capital punishment reduces serious crimes as its supporters claim. Yet politicians and commentators regularly claim that more punishments are a way to cut crime. Academic, government and community organisations have all said crime policies need to be based more on evidence, but much of the evidence available at the moment is poor or unclear. Debates about crime rarely reflect how strong the evidence behind opposing policies is, and even when politicians honestly believe they’re following the evidence, they tend to select evidence that supports their political views. This guide looks at some of the key things we do know and why it has been so difficult to make sense of crime policy. An important point throughout is that policymakers sometimes have to make decisions when things are not clear-cut. They have a better chance of making effective policies if they admit to this uncertainty – and conduct robust research to find out more. In the following pages we have shared insights from experts in violent crime, policing, crime science, psychology and the media’s influence on the crime debate. They don’t have all the answers, but we hope they leave you better-placed to hold policymakers and commentators to account and promote a more useful discussion about crime

A rank based social norms model of how people judge their levels of drunkenness whilst intoxicated

Background: A rank based social norms model predicts that drinkers’ judgements about their drinking will be based on the rank of their breath alcohol level amongst that of others in the immediate environment, rather than their actual breath alcohol level, with lower relative rank associated with greater feelings of safety. This study tested this hypothesis and examined how people judge their levels of drunkenness and the health consequences of their drinking whilst they are intoxicated in social drinking environments. Methods: Breath alcohol testing of 1,862 people (mean age = 26.96 years; 61.86 % male) in drinking environments. A subset (N = 400) also answered four questions asking about their perceptions of their drunkenness and the health consequences of their drinking (plus background measures). Results: Perceptions of drunkenness and the health consequences of drinking were regressed on: (a) breath alcohol level, (b) the rank of the breath alcohol level amongst that of others in the same environment, and (c) covariates. Only rank of breath alcohol level predicted perceptions: How drunk they felt (b 3.78, 95 % CI 1.69 5.87), how extreme they regarded their drinking that night (b 3.7, 95 % CI 1.3 6.20), how at risk their long-term health was due to their current level of drinking (b 4.1, 95 % CI 0.2 8.0) and how likely they felt they would experience liver cirrhosis (b 4.8. 95 % CI 0.7 8.8). People were more influenced by more sober others than by more drunk others. Conclusion: Whilst intoxicated and in drinking environments, people base judgements regarding their drinking on how their level of intoxication ranks relative to that of others of the same gender around them, not on their actual levels of intoxication. Thus, when in the company of others who are intoxicated, drinkers were found to be more likely to underestimate their own level of drinking, drunkenness and associated risks. The implications of these results, for example that increasing the numbers of sober people in night time environments could improve subjective assessments of drunkenness, are discussed

Orientation discrimination and contrast detection thresholds in migraine for cardinal and oblique angles

purpose. To determine whether orientation discrimination deficits in migraine, which have been found to depend on the spatial frequency of the stimulus, are due to precortical dysfunction or to abnormal patterns of orientation tuning at cortical loci. Further, to assess whether any cortical involvement is restricted to the striate cortex or whether higher cortical areas are also involved. Orientation-specific abnormalities would provide evidence of cortical dysfunction. methods. Orientation-discrimination and contrast-detection thresholds were assessed at cardinal (0°) and oblique (45°) orientations using explicit lines defined by Gabor patches. To test for extrastriate dysfunction, participants made orientation judgments using virtual lines defined by two widely spaced circles. Migraine history, migraine triggers, and pattern sensitivity were also assessed. Twenty migraineurs (10 with visual aura, 10 without) and 20 control participants were tested. results. Orientation-discrimination thresholds were lower for discriminations made about the cardinal axis than for discriminations made about the oblique axis, a well-documented phenomenon known as the oblique effect. Relative to the control group, the migraine group exhibited orientation-specific sensitivity losses on explicit and virtual judgments. Orientation-discrimination thresholds about the oblique axis were significantly elevated in the migraine group. In contrast, the migraine and control groups’ detection thresholds did not differ. conclusions. These findings reflect abnormal function of striate and extrastriate cortex in migraine. In addition, the discrimination data are consistent with wider orientation-tuning curves for orientation-sensitive cells in migraine, whereas the detection data suggest peak sensitivity does not differ between the groups

The ISCIP Analyst, Volume II, Issue 14

This repository item contains a single issue of The ISCIP Analyst, an analytical review journal published from 1996 to 2010 by the Boston University Institute for the Study of Conflict, Ideology, and Policy