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

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

A texture-processing model of the 'visual sense of number'

It has been suggested that numerosity is an elementary quality of perception, similar to colour. If so (and despite considerable investigation), its mechanism remains unknown. Here, we show that observers require on average a massive difference of approximately 40% to detect a change in the number of objects that vary irrelevantly in blur, contrast and spatial separation, and that some naive observers require even more than this. We suggest that relative numerosity is a type of texture discrimination and that a simple model computing the contrast energy at fine spatial scales in the image can perform at least as well as human observers. Like some human observers, this mechanism finds it harder to discriminate relative numerosity in two patterns with different degrees of blur, but it still outpaces the human. We propose energy discrimination as a benchmark model against which more complex models and new data can be tested

An inability to exclude visual noise in migraine

- Purpose: People with migraine are relatively poor at judging the direction of motion of coherently moving signal dots when interspersed with noise dots drifting in random directions, a task known as motion coherence. Although this has been taken as evidence of impoverished global pooling of motion signals, it could also arise from unreliable coding of local direction (of each dot), or an inability to segment signal from noise (noise-exclusion). The aim of this study was to determine how these putative limits contribute to impoverished motion processing in migraine. - Methods: Twenty-two participants with migraine (mean age, 34.7 ± 8.3 years; 16 female) and 22 age- and sex-matched controls (mean age, 34.4 ± 6.2 years) performed a motion-coherence task and a motion-equivalent noise task, the latter quantifying local and global limits on motion processing. In addition, participants were tested on analogous equivalent noise paradigms involving judgments of orientation and size, so that the specificity of any findings (to visual dimension) could be ascertained. - Results: Participants with migraine exhibited higher motion-coherence thresholds than controls (P = 0.01, independent t-test). However, this difference could not be attributed to deficits in either local or global processing since they performed normally on all equivalent noise tasks (P > 0.05, multivariate ANOVA). - Conclusions: These findings indicate that motion perception in the participants with migraine was limited by an inability to exclude visual noise. We suggest that this is a defining characteristic of visual dysfunction in migraine, a theory that has the potential to integrate a wide range of findings in the literature

Common Cortical Loci Are Activated during Visuospatial Interpolation and Orientation Discrimination Judgements

There is a wealth of literature on the role of short-range interactions between low-level orientation-tuned filters in the perception of discontinuous contours. However, little is known about how spatial information is integrated across more distant regions of the visual field in the absence of explicit local orientation cues, a process referred to here as visuospatial interpolation (VSI). To examine the neural correlates of VSI high field functional magnetic resonance imaging was used to study brain activity while observers either judged the alignment of three Gabor patches by a process of interpolation or discriminated the local orientation of the individual patches. Relative to a fixation baseline the two tasks activated a largely over-lapping network of regions within the occipito-temporal, occipito-parietal and frontal cortices. Activated clusters specific to the orientation task (orientation>interpolation) included the caudal intraparietal sulcus, an area whose role in orientation encoding per se has been hotly disputed. Surprisingly, there were few task-specific activations associated with visuospatial interpolation (VSI>orientation) suggesting that largely common cortical loci were activated by the two experimental tasks. These data are consistent with previous studies that suggest higher level grouping processes -putatively involved in VSI- are automatically engaged when the spatial properties of a stimulus (e.g. size, orientation or relative position) are used to make a judgement

The association between income inequality and adult mental health at the subnational level—a systematic review

Purpose A systematic review was undertaken to determine whether research supports: (i) an association between income inequality and adult mental health when measured at the subnational level, and if so, (ii) in a way that supports the Income Inequality Hypothesis (i.e. between higher inequality and poorer mental health) or the Mixed Neighbourhood Hypothesis (higher inequality and better mental health). Methods Systematic searches of PsycINFO, Medline and Web of Science databases were undertaken from database inception to September 2020. Included studies appeared in English-language, peer-reviewed journals and incorporated measure/s of objective income inequality and adult mental illness. Papers were excluded if they focused on highly specialised population samples. Study quality was assessed using a custom-developed tool and data synthesised using the vote-count method. Results Forty-two studies met criteria for inclusion representing nearly eight million participants and more than 110,000 geographical units. Of these, 54.76% supported the Income Inequality Hypothesis and 11.9% supported the Mixed Neighbourhood Hypothesis. This held for highest quality studies and after controlling for absolute deprivation. The results were consistent across mental health conditions, size of geographical units, and held for low/middle and high income countries. Conclusions A number of limitations in the literature were identified, including a lack of appropriate (multi-level) analyses and modelling of relevant confounders (deprivation) in many studies. Nonetheless, the findings suggest that area-level income inequality is associated with poorer mental health, and provides support for the introduction of social, economic and public health policies that ameliorate the deleterious effects of income inequality. Clinical registration number PROSPERO 2020 CRD42020181507

Retinal abnormalities contribute to S-cone selective deficits in migraine

Past studies have shown that individuals with migraine have elevated thresholds to S-cone stimuli relative to the control population (Shepherd, 2005 Cephalalgia 25 412 ^ 423). However, it is unclear whether this deficit arises from dysfunction at cortical or precortical sites. To localise the source of this abnormality within the visual pathways, an experimental paradigm called transient tritanopia was employed (Mollon and Polden, 1977 Philosophical Transactions of the Royal Society of London, Series B 278 207 ^ 240). Defined as a reduction in sensitivity to short-wavelength stimuli in response to the extinction of a long-wavelength adapting display, there is strong evidence to suggest that this phenomenon is retinal in origin (Valeton and Van Norren, 1979 Nature 280 488 ^ 490). Thirty-two participants with migraine (meeting the International Headache Society diagnostic criteria), and thirty-two age-matched/sex-matched control participants were tested to determine S-cone detection thresholds in a 4AFC procedure, both before and after adaptation to (1) a long-wavelength, and (2) a chromatically neutral display. In both groups, long-wavelength adaptation increased subsequent detection thresholds to S-cone stimuli. However, this loss of sensitivity was significantly greater in the migraine group. In contrast, adaptation to Tenth Applied Vision Association Christmas Meeting, Abstracts 427 a chromatically neutral display (equal in luminance to the long-wavelength display) had no effect on S-cone sensitivity. In conclusion, retinal abnormalities may contribute to a loss of sensitivity in the detection of short-wavelength stimuli in migraine

Evidence for precortical, potentially retinal-based, abnormalities of the visual system in migraine

Background In the retina, light is absorbed by the L-, M- and S-cone photoreceptors. Studies have shown that people with migraine perform worse than controls in experiments that assess sensitivity to S-cone stimuli. It is unclear whether these differences arise from dysfunction at cortical or precortical sites. Objective To localize the source of this abnormality, we took advantage of an experimental paradigm called transient tritanopia, in which observers exposed to a long wave-length adapting display experience a paradoxical reduction in sensitivity to short wave-length stimuli. There is strong evidence to suggest that this phenomenon is precortical/retinal in origin. Methods Participants with migraine and age-matched controls were tested to determine S-cone detection thresholds using a 4AFC procedure both before and after adaptation to (1) a long-wavelength (yellow) display, and (2) a control (grey) display. Results In both groups, adaptation to a long-wavelength display increased subsequent detection thresholds to S-cone stimuli. This loss of sensitivity was significantly greater in the migraine group. Loss of sensitivity following adaptation to a neutral display was minimal, and did not differ between groups. Conclusion Abnormalities in precortical sites may contribute to a loss of sensitivity in the detection of short-wavelength stimuli in migraine

Retinal abnormalities contribute to S-cone selective deficits in migraine

Past studies have shown that individuals with migraine have elevated thresholds to S-cone stimuli relative to the control population (Shepherd, 2005 Cephalalgia 25 412 ^ 423). However, it is unclear whether this deficit arises from dysfunction at cortical or precortical sites. To localise the source of this abnormality within the visual pathways, an experimental paradigm called transient tritanopia was employed (Mollon and Polden, 1977 Philosophical Transactions of the Royal Society of London, Series B 278 207 ^ 240). Defined as a reduction in sensitivity to short-wavelength stimuli in response to the extinction of a long-wavelength adapting display, there is strong evidence to suggest that this phenomenon is retinal in origin (Valeton and Van Norren, 1979 Nature 280 488 ^ 490). Thirty-two participants with migraine (meeting the International Headache Society diagnostic criteria), and thirty-two age-matched/sex-matched control participants were tested to determine S-cone detection thresholds in a 4AFC procedure, both before and after adaptation to (1) a long-wavelength, and (2) a chromatically neutral display. In both groups, long-wavelength adaptation increased subsequent detection thresholds to S-cone stimuli. However, this loss of sensitivity was significantly greater in the migraine group. In contrast, adaptation to Tenth Applied Vision Association Christmas Meeting, Abstracts 427 a chromatically neutral display (equal in luminance to the long-wavelength display) had no effect on S-cone sensitivity. In conclusion, retinal abnormalities may contribute to a loss of sensitivity in the detection of short-wavelength stimuli in migraine

The oblique effect in migraine

There has been recent interest in orientation discrimination in migraine. To date, however, performance has been tested at a single orientation only and group differences have either failed to emerge, or have been found to depend on the spatial frequency of the stimulus. Consequently, it is unclear whether elevated thresholds in migraine are due to precortical dysfunction, or abnormal patterns of orientation tuning at cortical loci. A reduced sensitivity to oblique stimuli (the oblique effect) is thought to reflect cortical processing, eg a population bias at V1 and/or narrower tuning of cells tuned to cardinal stimuli due to recurrent intracortical synaptic connections. Orientation discrimination thresholds were calculated by using explicitly-drawn Gabor patches at cardinal (08) and oblique (458) orientations. In parallel, participants made orientation judgments using non-explicit (virtual) lines defined by two widely spaced circles that could not stimulate V1 receptive fields. Twenty migraine and twenty matched control participants were tested. Relative to the control group, the migraine group exhibited orientation-specific sensitivity losses on explicit and virtual judgments: orientation discrimination thresholds were significantly elevated in migraine about the oblique axis only. These findings reflect abnormal function of the striate and extrastriate cortex in migraine