Motion Processing Deficits in Migraine

Avaliação da sensibilidade ao contraste em pacientes com migrânea

O objetivo foi medir a Função de Sensibilidade ao Contraste (FSC) de pacientes com migrânea e de voluntários saudáveis sem a patologia. Participaram dos testes 12 voluntários do sexo feminino, seis com migrânea e seis sem migrânea na faixa etária de 20 a 37 anos. As medidas de FSC foram realizadas utilizando estímulos visuais estáticos de grades senoidais angulares com frequências espaciais de 2, 3, 4, 24 e 64 ciclos/360º Foi utilizado o método psicofísico da escolha forçada entre duas alternativas temporais, condições de luminância fotópica (luminância média da tela de 41 cd/m²) e visão binocular com pupila natural. Os resultados demonstram que a percepção visual de contraste dos voluntários com migrânea foi menor nas frequências de 2, 3, 4 e 64 ciclos/360º. Esses achados preliminares sugerem alterações na FSC relacionadas a essa patologia.

Migraine and motion sickness independently contribute to visual discomfort

The objective of this study was to evaluate, in patients with migraine and healthy volunteers, with and without a history of motion sickness, the degree of discomfort elicited by drifting striped patterns. Eighteen healthy volunteers (HV) and 30 migraine patients participated in the study. Discomfort was greater in migraine patients than in HV, and in individuals with a history of motion sickness than in those without, but the effect of history of migraine was independent of history of motion sickness. Generalized Estimating Equations models for binary correlated data revealed that these differences did not depend on levels of duty cycle, spatial and temporal frequencies. Visual discomfort in migraine patients was associated with worse performance. There was a significant correlation between median degree of discomfort across conditions and number of migraine attacks in the past month. Discomfort to drifting striped patterns may be related to central sensitization in migraine patients.

Differential activation of the middle-temporal complex to visual stimulation in migraineurs

Objective: Differences between people with and without migraine on various measures of visual perception have been attributed to abnormal cortical processing due to the disease. The aim of the present study was to explore the dynamics of the basic interictal state with regard to the extrastriate, motion-responsive middle temporal area (MT-complex) with functional magnetic resonance imaging (fMRI) at 3 tesla using coherent/incoherent moving dot stimuli.

Method: Twenty-four migraine patients (12 with aura [MwA], 12 without aura [MwoA]) and 12 healthy subjects participated in the study. The individual cortical folding pattern was accounted for by using a cortical matching approach.

Results: In the inferior-posterior portion of the MT-complex, most likely representing MT, control subjects showed stronger bilateral activation compared to MwA and MwoA patients. Compared with healthy controls MwoA and MwA patients showed significantly stronger activation mainly at the left side in response to visual stimulation in the superior-anterior portion of the MT-complex, representing the medial-superior temporal area (MST).

Conclusion: Our findings strengthen the hypothesis that hyperresponsiveness of the visual cortex in migraine goes beyond early visual areas, even in the interictal period.

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.

Is the development of visual contrast sensitivity impaired in children with migraine? An exploratory study

Introduction: Impairment of visual contrast sensitivity is a well-known phenomenon in adult migraineurs. Little is known, however, about whether contrast sensitivity deficits are already present in children with migraine.

Methods: We conducted an exploratory study with 18 children with migraine without aura, in which we tested our subjects’ visual contrast sensitivity. Eighteen age- and sex-matched healthy children served as controls.

Results: Among the youngest subjects (6–10 years) we found no significant differences at any of the spatial frequencies tested, as compared to the controls, whereas from the age of 10 on, migraineurs exhibited significantly poorer contrast sensitivity, especially at the lower spatial frequencies.

Conclusion: To our knowledge, we are the first to report on such a deficit in children, and we conclude that our findings might be interpreted as reflecting an increased vulnerability of the visual system to migraine attacks as part of the migrainous endophenotype.

Perceptive aspects of visual aura

Visual aura is the most common feature associated with migraine, though it can occur separately. In both cases it often represents a dramatic event, especially for patients who experience it for the first time. Besides, its subjective characteristics may illuminate on the functional architecture of the visual cortex. Repetitive events of migraine and visual aura have been suggested to affect the visual system in the long run, both on the cortical and precortical level. In effect, objective investigation of visual functions in patients support the idea that a selective damage does occur, so that more attention to visual examination seems to be justified. In this paper, subjective and psychophysical aspects of visual aura are examined, lastly highlighting and discussing the interesting correlations found between this condition and normal-tension glaucoma.

Global visual processing and self-rated autistic-like traits

The current research investigated, firstly, whether individuals with high levels of mild autistic-like traits display a similar profile of embedded figures test (EFT) and global motion performance to that seen in autism. Secondly, whether differences in EFT performance are related to enhanced local processing or reduced global processing in the ventral visual stream was also examined. Results indicated that people who scored high on the Autism-spectrum Quotient (AQ) were faster to identify embedded figures, and had poorer global motion and global form thresholds than low AQ scorers. However, the two groups did not differ on a task assessing lower-level input to the ventral stream. Overall the results indicate that individuals with high levels of autistic-like traits have difficulties with global integration in the visual pathways, which may at least partly explain their superior EFT performance.

Low spatial frequency contrast sensitivity deficits in migraine are not visual pathway selective

Some people who experience migraine demonstrate reduced visual contrast sensitivity that is measurable between migraines. Contrast sensitivity loss to low spatial frequency gratings has been previously attributed to possible impairment of magnocellular pathway function. This study measured contrast sensitivity using low spatial frequency targets (0.25-4 c/deg) where the adaptation aspects of the stimuli were designed to preferentially assess either magnocellular or parvocellular pathway function (steady and pulsed pedestal technique). Twelve people with migraine with measured visual field abnormalities and 17 controls participated. Subjects were tested foveally and at 10 degrees eccentricity. Foveally, there was no significant difference in group mean contrast sensitivity. At 10 degrees , the migraine group demonstrated reduced contrast sensitivity for both the stimuli designed to assess magnocellular and parvocellular function (P < 0.05). The functional deficits measured in this study infer that abnormalities of the low spatial frequency sensitive channels of both pathways contribute to contrast sensitivity deficits in people with migraine.

Binocular rivalry in migraine

Cortical hyperexcitability in migraine could arise from abnormally weak inhibition or from strengthened intracortical excitatory mechanisms. The present study employed binocular rivalry to differentiate between these possibilities. Rivalry between static oriented grating patterns was examined in migraine with aura (MA), migraine without aura (MoA) and headache-free control participants. A non-significant trend toward elevated mean dominance intervals (monocular percepts, in seconds) was seen in both migraine groups at all contrasts. Second, significant interocular differences in rivalry dominance durations were seen in the MoA group compared with controls; this difference also approached significance in the MA group. Finally, both MA and MoA exhibited significantly greater visual discomfort than the control group in the presence of both static stripes and flickering visual stimuli. The rivalry results provide no support for weakened intracortical inhibition in migraine. Optical or neural precortical differences in the eyes' input strengths paired with enhanced recurrent cortical excitation can explain these findings.

Triggers of Motion Sickness in Migraine Sufferers

OBJECTIVE

To determine whether susceptibility to motion sickness provoked by unexpected movement is associated with susceptibility to visually induced motion sickness in migraine sufferers.

BACKGROUND

Migraine sufferers are unusually susceptible to motion sickness, but the mechanism of this susceptibility is not well understood. Possibilities include vestibular dysfunction secondary to vasomotor disturbances during migraine attacks, hyperexcitability of brainstem circuits that produce symptoms of motion sickness and migraine, and heightened susceptibility to visual illusions of movement.

METHOD

A motion sickness susceptibility questionnaire that listed common triggers of motion sickness was filled out by 42 migraine sufferers and 39 headache-free controls of similar age and sex distribution to migraine sufferers.

RESULTS

A greater proportion of migraine sufferers than controls reported that traveling in cars and buses, reading in the car, using playground equipment, watching wide-screen movies and movement simulators, induced motion sickness. However, visually induced motion sickness appeared to be independent of motion sickness to most movement-related stimuli in migraine sufferers.

CONCLUSIONS

The lack of association between susceptibility to movement-induced and visually induced motion sickness implies that more than one mechanism increases susceptibility to motion sickness in migraine sufferers.

Abnormal visual processing in migraine with aura: a study of steady-state visual evoked potentials

BACKGROUND

Although a number of studies reported different interictal findings between migraine with aura (MA) and migraine without aura (MO), the pathophysiology of the visual aura in migraine remains unclear.

OBJECTIVE

To investigate the visual processing in patients who experience MA between attacks using steady-state visual evoked potentials (SSVEPs).

METHODS

SSVEPs to high (98%) and low (29%) contrast black and white checkerboard gratings with two spatial frequencies (0.5 and 2.0 cpd) at 5 and 10 Hz (10 and 20 reversal/s) were recorded binocularly from 10 patients with MA, 10 patients with MO between attacks and 20 healthy controls (HC). The SSVEPs were Fourier analyzed to obtain the amplitude and phase of the second (2F) and fourth (4F) harmonic response.

RESULTS

In the amplitude of 2F, at 0.5 cpd, there was significant increased amplitude in both MA and MO in comparison to HC at 5 Hz in high and low contrast. However, no significant differences were detected at 2.0 cpd in both 5 and 10 Hz in high and low contrast. In the amplitude of 4F, at 2.0 cpd, there was significant increased amplitude in MA in comparison to MO and HC at 10 Hz in high contrast. However, there were no significant differences at 0.5 cpd at both 5 and 10 Hz in high and low contrast. There were no significant phase differences between MA, MO, and HC.

CONCLUSION

The high amplitude of the SSVEPs suggests that interictally migraine patients have abnormal excitability in the primary visual cortex, and this change in excitability may exist, at least partially, in the visual association cortex in MA.

Spreading Depression Enhances Human Neocortical Excitability in vitro

Cortical spreading depression (CSD) plays a role in migraine with aura. However, studies of the neuronal effects of CSD in human cortex are scarce. Therefore, in the present study, the effects of CSD on the field excitatory postsynaptic potentials (fEPSP) and the induction of long-term potentiation (LTP) were investigated in human neocortical slices obtained during epilepsy surgery. CSD significantly enhanced the amplitude of fEPSP following a transient suppressive period and increased the induction of LTP in the third layer of neocortical tissues. These results indicate that CSD facilitates synaptic excitability and efficacy in human neocortical tissues, which can be assumed to contribute to hyperexcitability of neocortical tissues in patients suffering from migraine.

The brain is hyperexcitable in migraine

Migraine is a very common disorder occurring in 20% of women and 6% of men. Central neuronal hyperexcitability is proposed to be the putative basis for the physiological disturbances in migraine. Since there are no consistent structural disturbances in migraine, physiological and psychophysical studies have provided insight into the underlying mechanisms. This is a review of the neurophysiological studies which have provided an insight to migraine pathogenesis supporting the theory of hyperexcitability.

The cerebellum and migraine

Clinical and pathophysiological evidences connect migraine and the cerebellum. Literature on documented cerebellar abnormalities in migraine, however, is relatively sparse. Cerebellar involvement may be observed in 4 types of migraines: in the widespread migraine with aura (MWA) and migraine without aura (MWoA) forms; in particular subtypes of migraine such as basilar-type migraine (BTM); and in the genetically driven autosomal dominant familial hemiplegic migraine (FHM) forms. Cerebellar dysfunction in migraineurs varies largely in severity, and may be subclinical. Purkinje cells express calcium channels that are related to the pathophysiology of both inherited forms of migraine and primary ataxias, mostly spinal cerebellar ataxia type 6 (SCA-6) and episodic ataxia type 2 (EA-2). Genetically driven ion channels dysfunction leads to hyperexcitability in the brain and cerebellum, possibly facilitating spreading depression waves in both locations. This review focuses on the cerebellar involvement in migraine, the relevant ataxias and their association with this primary headache, and discusses some of the pathophysiological processes putatively underlying these diseases.

Visual stimuli are common triggers of migraine and are associated with pattern glare

OBJECTIVE

To investigate the associations between interictal pattern glare, visual stress, and visual triggers of migraine.

BACKGROUND

There has been relatively little research on the visual stimuli that can trigger migraine episodes. This is surprising, since if practitioners can obviate such triggers, then some attacks may be prevented. The existing literature suggests that patients who are prone to visually triggered migraines report more illusions on viewing striped patterns ("pattern glare") and that colored filters may be an effective intervention for these people.

METHODS

Headache symptoms and headache triggers were investigated in migraine and control groups in 2 separate experiments. In one experiment, we also determined, for each participant, pattern glare, whether it was reduced by colored filters and, if so, what the optimum color of filter was. Color vision was also assessed with the D15 test.

RESULTS

People with migraine saw significantly more illusions on viewing each striped pattern and experienced greater pattern glare. They were also more likely to select a colored filter to aid visual comfort, particularly colors in the blue-to-green sector of the spectrum. Color vision was impaired subtly but significantly in migraine. Principal component analyses grouped common headache triggers into 5 broadly equal components: food, visual triggers, alcohol, stress and tiredness, and the environment. In a second analysis, the overall number of illusions seen in striped patterns was associated with visual triggers while pattern glare, use of colored filters, and interictal light sensitivity together formed a sixth component interpreted as visual stress.

CONCLUSIONS

It is suggested that clinicians should ask migraine patients whether visual stimuli trigger their migraine, about interictal visual symptoms, and use the pattern glare test to ensure that those who may benefit from optometric interventions are appropriately managed.

Anatomical alterations of the visual motion processing network in migraine with and without aura

BACKGROUND

Patients suffering from migraine with aura (MWA) and migraine without aura (MWoA) show abnormalities in visual motion perception during and between attacks. Whether this represents the consequences of structural changes in motion-processing networks in migraineurs is unknown. Moreover, the diagnosis of migraine relies on patient's history, and finding differences in the brain of migraineurs might help to contribute to basic research aimed at better understanding the pathophysiology of migraine.

METHODS AND FINDINGS

To investigate a common potential anatomical basis for these disturbances, we used high-resolution cortical thickness measurement and diffusion tensor imaging (DTI) to examine the motion-processing network in 24 migraine patients (12 with MWA and 12 MWoA) and 15 age-matched healthy controls (HCs). We found increased cortical thickness of motion-processing visual areas MT+ and V3A in migraineurs compared to HCs. Cortical thickness increases were accompanied by abnormalities of the subjacent white matter. In addition, DTI revealed that migraineurs have alterations in superior colliculus and the lateral geniculate nucleus, which are also involved in visual processing.

CONCLUSIONS

A structural abnormality in the network of motion-processing areas could account for, or be the result of, the cortical hyperexcitability observed in migraineurs. The finding in patients with both MWA and MWoA of thickness abnormalities in area V3A, previously described as a source in spreading changes involved in visual aura, raises the question as to whether a "silent" cortical spreading depression develops as well in MWoA. In addition, these experimental data may provide clinicians and researchers with a noninvasively acquirable migraine biomarker.

Do migraineurs have difficulty judging direction of simulated heading?

Some migraineurs have increased thresholds for the detection of global dot motion. We investigated whether migraineurs show consequential abnormalities in the determination of direction of self-motion (heading) from simulated optic flow. The ability to determine heading from optic flow is likely to be necessary for optimal determination of self-motion through the environment. Twenty-five migraineurs and 25 controls participated. Global dot motion coherence thresholds were assessed, in addition to performance on two simulated heading tasks: one with a symmetrical flow field, and the second with differing velocity of optic flow on the left and right sides of the participant. While some migraineurs demonstrated abnormal global motion coherence thresholds, there was no difference in performance on the heading tasks at either simulated walking (5 km/h) or driving (50 km/h) speeds. Increased global motion coherence thresholds in migraineurs do not result in abnormal judgements of heading from 100% coherent optic flow.

Ocular motor measures in migraine with and without aura

The purpose of this study was to examine basic ocular motor function in individuals with migraine. We used an infrared eye-tracking system to measure horizontal smooth pursuit to a sinusoidal target, saccades to horizontal target displacements of 5-20 degrees , and the stability of fixation in 19 migraine without aura (MoA), 19 migraine with aura (MA) and 19 headache-free control (C) subjects. Eye movement measurements were made at two target displacement rates and against both homogeneous grey and patterned backgrounds. We found no statistically significant differences between migraine and control subjects in any of the eye movement parameters measured, but did find highly significant effects of both target speed and background pattern in all groups. Our results do not provide support for subclinical cerebellar impairment in migraineurs, and do provide evidence that previously described visual abnormalities in migraine are not artefacts of abnormal fixation or eye movements.

Altered motion perception in migraineurs: evidence for interictal cortical hyperexcitability

Much research on visual functions in migraine has pinpointed the existence of abnormal visual processing between attacks. However, it is not clear if this is due to cortical hyper- or hypoexcitability. We aimed to clarify this issue by comparing motion perception thresholds of subjects with migraine with (MA) or without aura (MoA) and control subjects. Two types of dot kinetograms were used: in the first experiment coherently moving dots were presented in an incoherent environment, while in the second only coherent motion was seen. Subjects with migraine displayed significantly impaired motion perception compared with controls when they had to detect the direction of the coherently moving dots in an incoherent environment, while they were slightly better in a direction discrimination task, where only coherent motion was presented. This pattern of results is comparable to those achieved by an external excitability enhancement of V5 induced in healthy human subjects in a former study of our group. According to this, a cortical excitability enhancement can result in an impaired focusing on a given signal against a noisy background, but improves perception of non-ambiguous stimuli. Thus we conclude that migraineurs display enhanced visual cortical excitability between attacks in V5.

Processing of global form and motion in migraineurs

Previous studies have identified anomalies of cortical visual processing in migraineurs that appear to extend beyond V1. Migraineurs respond differently than controls to transcranial magnetic stimulation of V5, and can demonstrate impairments of global motion processing. This study was designed to assess the integrity of intermediate stages of both motion and form processing in people with migraine. We measured the ability to integrate local orientation information into a global form percept, and to integrate local motion information into a global motion percept. Control subjects performed significantly better than migraineurs on both tasks, suggesting a diffuse visual cortical processing anomaly in migraine.

Frequency doubling technology perimetry and standard automated perimetry in migraine

The literature suggests that visual field defects may be more common in people who experience migraine. The Humphrey frequency doubling (FDT) visual field instrument selectively examines the magnocellular visual pathway, but has not previously been used to investigate visual function in migraine. In a masked controlled study we compared Humphrey FDT and Humphrey Swedish Interactive Threshold Algorithm fields of 25 migraine sufferers with 25 age- and gender-matched controls. Although both mean deviation and pattern standard deviation were a little worse in the migraine group, these differences did not reach statistical significance. There were no inter-eye visual field differences in the migraine group compared with controls. Comparing the mean of all the contrast thresholds in each hemisphere, there were no more inter-hemifield visual field differences in the migraine group compared with controls. There was no significant difference between the migraine and control groups in intra-ocular pressures. The visual field parameters were not correlated with the interval since the last migraine headache, the severity of migraine headache, the duration of migraine headache or the number of migraine headaches per annum. In our data, there was no evidence of visual field deficits, a magnocellular deficit, or indications of glaucomatous pathology.