Color Vision but not Visual Attention Is Altered in Migraine

Neural correlates of visuospatial processing in migraine: does the pain network help?

Migraine patients frequently report cognitive symptoms during the different phases of migraine. The most affected cognitive domains are visuospatial abilities, processing speed, attention and executive functions. We explored migraine patients' performance during a visuospatial task and investigated the activity of brain areas involved in visuospatial processing. A functional magnetic resonance imaging (MRI) visuospatial task, including an angle and a colour discrimination paradigm, was administrated to 17 headache-free migraine patients and 16 controls. Correlations between functional MRI abnormalities and subjects' performance, clinical and neuropsychological variables were also investigated. Deficits at visuospatial cognitive tests were present in around 20% of patients. Migraine patients maintained a preserved behavioural performance (reaction time and number of correct responses) during the angle discrimination task, while they performed less correctly in the colour task compared to controls (p = 0.05).The comparison of angle vs. colour task revealed an increased activity of the right insula, bilateral orbitofrontal cortex and medial frontal gyrus, and decreased activity of the bilateral posterior cingulate cortex in migraine patients compared to controls. In migraine patients, a better performance in the angle task was associated with higher activation of the right insula and orbitofrontal cortex, as well as with decreased activation of the right posterior cingulate cortex. Our results suggest an adaptive functional plasticity that might help migraine patients to overcome impaired visuospatial skills and preserve an adequate performance during a visuospatial task. These compensatory mechanisms seem to take advantage of recruiting brain areas that are commonly involved also in nociception.

Chromatic Induction in Migraine

The human visual system is not a colorimeter. The perceived colour of a region does not only depend on its colour spectrum, but also on the colour spectra and geometric arrangement of neighbouring regions, a phenomenon called chromatic induction. Chromatic induction is thought to be driven by lateral interactions: the activity of a central neuron is modified by stimuli outside its classical receptive field through excitatory-inhibitory mechanisms. As there is growing evidence of an excitation/inhibition imbalance in migraine, we compared chromatic induction in migraine and control groups. As hypothesised, we found a difference in the strength of induction between the two groups, with stronger induction effects in migraine. On the other hand, given the increased prevalence of visual phenomena in migraine with aura, we also hypothesised that the difference between migraine and control would be more important in migraine with aura than in migraine without aura. Our experiments did not support this hypothesis. Taken together, our results suggest a link between excitation/inhibition imbalance and increased induction effects.

Visual Perception in Migraine: A Narrative Review

Migraine, the most frequent neurological ailment, affects visual processing during and between attacks. Most visual disturbances associated with migraine can be explained by increased neural hyperexcitability, as suggested by clinical, physiological and neuroimaging evidence. Here, we review how simple (e.g., patterns, color) visual functions can be affected in patients with migraine, describe the different complex manifestations of the so-called Alice in Wonderland Syndrome, and discuss how visual stimuli can trigger migraine attacks. We also reinforce the importance of a thorough, proactive examination of visual function in people with migraine.

Visual Evoked Potential Responses after Photostress in Migraine Patients and Their Correlations with Clinical Features

In the past few years, researchers have detected subtle macular vision abnormalities using different psychophysical experimental tasks in patients with migraine. Recording of visual evoked potential (VEP) after photostress (PS) represents an objective way to verify the integrity of the dynamic properties of macular performance after exposure to intense light. VEPs were recorded before and after PS in 51 patients with migraine (19 with aura (MA) and 22 without aura (MO) between attacks, and 10 recorded during an attack (MI)) and 14 healthy volunteers. All study participants were exposed to 30 s of PS through the use of a 200-watt bulb lamp. The P100 implicit time and N75-P100 amplitude of the baseline VEP were compared with those collected every 20 s up to 200 s after PS. VEP parameters recorded at baseline did not differ between groups. In all groups, the VEP recordings exhibited a significant increase in implicit times and a reduction in amplitude at 20 s after the PS. In migraine, the percentage decrease in amplitudes observed at 20 s after photostress was significantly lower than in healthy volunteers, in both MO and MA patients, but not in MI patients. When data for MO and MA patients were combined, the percentage of amplitude change at 20 s was negatively correlated with the number of days that had elapsed since the last migraine attack, and positive correlated with attack frequency. We showed dynamic changes of recovery of VEP after PS depending on the migraine cycle. This finding, in conjunction with those previously attained with other neuromodulatory interventions using VEPs, leads us to argue that migraine-disease-related dysrhythmic thalamocortical activity precludes amplitude suppression by PS.

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.

Visual processing in migraine

Background

Migraine is a common neurological condition that often involves differences in visual processing. These sensory processing differences provide important information about the underlying causes of the condition, and for the development of treatments.

Review of psychophysical literature

Psychophysical experiments have shown consistent impairments in contrast sensitivity, orientation acuity, and the perception of global form and motion. They have also established that the addition of task-irrelevant visual noise has a greater effect, and that surround suppression, masking and adaptation are all stronger in migraine.

Theoretical signal processing model

We propose utilising an established model of visual processing, based on signal processing theory, to account for the behavioural differences seen in migraine. This has the advantage of precision and clarity, and generating clear, falsifiable predictions.

Conclusion

Increased effects of noise and differences in excitation and inhibition can account for the differences in migraine visual perception. Consolidating existing research and creating a unified, defined theoretical account is needed to better understand the disorder.

Acquired equivalence and related memory processes in migraine without aura

Introduction

Interictal deficits of elementary visuo-cognitive functions are well documented in patients with migraine and are mostly explained in terms of neocortical hyperexcitability. It has been suggested that the basal ganglia and the hippocampi might also be affected in migraine. If so, a deterioration of learning and memory processes related to these structures is expected.

Methods

A visual learning paradigm thought to be capable of dissociating learning/memory processes mediated by the basal ganglia from processes mediated by the hippocampus (the Rutgers Acquired Equivalence Test) was applied to a group of patients with migraine without aura and to age- and sex-matched controls.

Results

Patients with migraine showed a significantly poorer performance in both main phases of the test and the deficit in the phase considered to be dependent on the hippocampi was especially marked.

Conclusions

These results can be interpreted as behavioural support for findings that have suggested the involvement of the basal ganglia and the hippocampi in migraine, but further research is needed to clarify these findings.

Is Male Migraine Associated With Color Vision Deficiency? Findings Among Israeli Adolescents Between 2007 and 2013

OBJECTIVE

Accumulating clinical and experimental evidence has shown that migraine patients tend to suffer from color vision abnormalities. The aim of this study was to examine whether color vision deficiency is associated with male migraine in a large population of adolescents.

METHODS

The study population included all Israeli male adolescents who underwent medical and cognitive examinations as part of their recruiting process between the years 2007 and 2013. Migraine prevalence among patients with color vision deficiency was compared to that of males without substantial color vision abnormalities.

RESULTS

The study population included 305 964 male adolescents at the age of 17 ± 0.6, of whom 7584 (2.5%) had color vision deficiency, as determined by the Farnsworth Panel D-15 color blindness test. Males with color vision deficiency had a 32% increased prevalence of migraine as compared with the control group (odds ratio 1.32, 95% confidence interval 1.18-1.48, P < .001), after adjusting for multiple variables.

CONCLUSIONS

The authors found an association between color vision deficiency and migraine in male adolescents. The study results lay the basis for further research into male migraine, as well as the visual aspects of migraine.

Migraine with aura is associated with impaired colour vision: Results from the cross-sectional German DMKG headache study

BACKGROUND

Hypersensitivity to light, noise and odour are pivotal clinical characteristics of migraine associated with enhanced cortical excitability and dysfunctional habituation. However, little is known about the integrity of basic sensory functioning in migraine on a population-based level.

METHODS

A total of 129 participants with migraine (105 without aura, MwoA, 24 with aura, MA) and 522 healthy controls without headache 12 months prior to baseline were included from a sample of the DMKG study and underwent standardised clinical sensory testing of smell, taste, hearing and vision.

RESULTS

After adjustment for age, sex, smoking status and history of head injuries, the chance of impaired colour perception was significantly higher in MA compared to controls (odds ratio, OR=3.20; 95% CI=1.20-8.53) and MwoA (OR=3.62; 95% CI=1.31-9.97). Compared to MwoA, MA also had an increased chance of smell (OR=3.20; 95% CI=0.98-10.42) and taste (OR=2.58; 95% CI=0.90-7.40) impairment.

CONCLUSIONS

In this cross-sectional, population-based study on sensory functioning in migraine participants, colour vision was impaired interictally in MA compared to MwoA and controls.

Is the migrainous brain normal outside of acute attacks? Lessons learned from psychophysical, neurochemical and functional neuroimaging studies

Migraine is a largely inherited disorder of the brain with recurrent head pain attacks. There is an increasing awareness, however, that the manifestation of migrainous biology is not restricted to such acute head pain attacks, but that migraine is rather a disorder with a continuous complex and broad sensory processing dysfunction in which normal sensory stimuli (somatosensory, visual, auditory and olfactory) are misinterpreted by the brain. This dysfunction is most prominent during attacks, but there are more and more evidences that the processing and perception of stimuli is abnormal also outside of attacks to a varying degree. In this topical review, we will summarize and discuss the current clinical, neurochemical and functional neuroimaging literature on this paradigm shift from a strictly episodic head pain disorder to migraine as a more general dysfunction of sensory processing.

Methods for studying naturally occurring human pain and their analogues

Methods for investigating human pain have been developed over the last 100years. Typically, researchers focus on people with clinical pain, or on healthy participants undergoing laboratory-controlled pain-induction techniques focussed mostly on exogenously generated skin nociception. Less commonly investigated are acute pain experiences that emerge naturally. Six common painful complaints were identified: headache, muscular pain, visceral pain, menstrual pain, dental pain, and pain associated with upper respiratory tract infection. Methods used to recruit participants with the natural occurrence of each pain complaint were identified, and features of their use reviewed. Also reviewed were experimental analogues designed to mimic these pains, with the exception of menstrual pain. Headache and menstrual pain appear to be most effectively researched in their naturally occurring form, whereas muscle and dental pain may be more easily induced. Upper respiratory tract infection and abdominal pain provide further challenges for researchers. Summary guidance is offered, and directions for methods development outlined.

Reflexive attentional orienting in migraineurs: The behavioral implications of hyperexcitable visual cortex

Introduction: Although migraine is classified as a headache disorder, a key part of migraine pathophysiology is a heightened excitability of visual cortices in between headache events. The goal of our study was to examine the behavioral impact of this visuocortical hyperexcitability, in terms of its effect on reflexive visual attentional orienting.

Methods and results: In Experiment 1, using a non-predictive spatial cuing task that relied on sensory-evoked responses in the visual cortex for triggering attentional orienting, we found that migraineurs had greater attentional enhancement of manual target responses, relative to non-migraine controls. In two control experiments we confirmed that this heightened attention effect in migraineurs is not due to exaggerated reflexive orienting responses in general, but rather, it appears to be specifically associated with sensory-evoked attentional triggers.

Discussion: Taken together, this confirms that the functional consequences of hyperexcitable visual cortex in migraineurs are not just purely sensory in nature, but directly impact at least some forms of reflexive attention. This provides evidence of at least one cognitive implication of hyperexcitable visual cortical responses in migraineurs, namely heightened reflexive visual-spatial orienting specific to sudden-onset peripheral events.

Visual metacontrast masking in migraine

Background: In visual metacontrast masking, the visibility of a brief target stimulus can be reduced substantially if it is preceded (forward masking) or followed (backward masking) by a non-overlapping mask. These effects have been attributed to inhibitory processes within the visual system. Two previous studies have used metacontrast masking to assess inhibitory function in migraine and control groups, however, each used different types of masking and obtained different results.

Subjects and Methods: Forward, backward and combined forward and backward masking were compared in migraine (15 with visual aura, 15 without) and control ( n = 15) groups. Baseline trials were also included (target only).

Results: For all types of masking, both migraine groups were more accurate than the control group. When performance for the masking trials was expressed relative to baseline, however, there were no significant group differences. Performance in certain conditions nevertheless correlated significantly with migraine frequency and with the recency of the last attack.

Conclusions: The inhibitory processes involved in the masking tasks employed in this study do not appear to be impaired in migraine. Their better overall performance may reflect a sensitivity difference, perhaps as a consequence of a heightened neuronal response, which varies with the migraine cycle.

Asymmetry of visual function in migraine with aura: Correlation with lateralisation of headache and aura

Background: Asymmetry of visual phenomena and headache is an important feature of migraine with aura.

Methods: This asymmetry was explored by assessment of visual illusions, hemifield spatial contrast detection (HCD) and hemifield pattern reversal visual evoked potentials (HVEPs) in 47 migraineurs with aura (MA), who were not taking prophylactic medications, and 62 controls with the same age range (16–59).

Results: Illusions were greater and HCD was poorer in MA than in controls. There were no group differences with respect to P100 amplitude. The longer the duration of migraine the poorer the HCD. When the aura was consistently unilateral it was associated with greater illusions, reduced HCD and reduced hemifield P100 amplitude. These findings were not related to the side of headache.

Conclusion: The lateralised changes suggest that the visual dysfunction occurs at a cortical level, and the correlation with the side of the aura suggests that dysfunction is most likely to occur in an area of preexisting anomaly of neural function.