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Migraine is a common neurological disorder with strong links to vision. Interictal migraine is thought to be characterised by internal noise in the brain, possibly due to increased variability in neural firing, which can be estimated... more
Migraine is a common neurological disorder with strong links to vision. Interictal migraine is thought to be characterised by internal noise in the brain, possibly due to increased variability in neural firing, which can be estimated using equivalent noise tasks. High-frequency transcranial random noise stimulation (hf-tRNS) can be used to modulate levels of internal noise in the brain, and so presents a possible therapy to redress noise levels in the migraine brain. This is a case-control study using a 2-alternative forced choice (2AFC) design. hf-tRNS and Sham control stimulation were used alongside a global motion direction discrimination task and visually based equivalent noise tasks. The migraine group demonstrated increased baseline internal noise levels compared to the control group. Internal noise levels, and sampling, were reduced using hf-tRNS but not Sham stimulation. However, there were no differences in terms of coherence thresholds, slopes, and lapse rate for global motion discrimination between the two groups. This is the first demonstration of the possibility of decreasing internal noise levels in migraine using hf-tRNS. Future work could explore the possibility of neurostimulation as a therapy for migraine.
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Individuals with migraine tend to experience discomfort when viewing flickering stimuli. It has been suggested that one of the characteristics of migraine is a lack of habituation to repetitive visual stimuli, although findings can be... more
Individuals with migraine tend to experience discomfort when viewing flickering stimuli. It has been suggested that one of the characteristics of migraine is a lack of habituation to repetitive visual stimuli, although findings can be mixed. Previous work has typically used similar visual stimuli (chequerboard) and only one temporal frequency. This study systematically varied the spatial and temporal characteristics of the visual stimulus, using steady‐state visual evoked potentials to assess the differences in amplitude between migraine and control group over consecutive blocks of stimulation. Twenty individuals with migraine and 18 control observers were asked to rate their visual discomfort after viewing sequences of flickering Gabor patches with a frequency of either 3 or 9 Hz across three different spatial frequencies (low 0.5 cpd; mid‐range 3 cpd; high 12 cpd). Compared to the control group, the migraine group showed a reduction in SSVEP responses with increased exposure, suggesting habituation processes are intact at 3‐Hz stimulation. However, at 9‐Hz stimulation, there was evidence of increased responses with increasing exposure in the migraine group in particular, which might suggest a build‐up of the response over repetitive presentations. Visual discomfort varied with spatial frequency, for both 3‐ and 9‐Hz stimuli, the highest spatial frequencies were the least uncomfortable compared to the low‐ and mid‐range spatial frequencies in both groups. This difference in SSVEP response behaviour, dependent on temporal frequency, is important to consider when researching the effects of repetitive visual stimulation in migraine and could give some indication of build‐up of effects leading to aversion to visual stimuli.
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Designing a robust classification mechanism with a higher accuracy for Electroencephalogram (EEG) signals is a challenging task. In this paper, a metaheuristic based multi-objective fuzzy modelling mechanism based on the One-Against-One... more
Designing a robust classification mechanism with a higher accuracy for Electroencephalogram (EEG) signals is a challenging task. In this paper, a metaheuristic based multi-objective fuzzy modelling mechanism based on the One-Against-One (OAO) strategy has been developed for classification of multiclass steady state visual evoked potential (SSVEP) data. In this work, three different flickering frequencies in 10Hz, 14Hz and 21Hz were used to elicit the SSVEPs. The recorded EEG signals were segmented into 2.5-second long epochs and features were extracted using the Discrete Wavelet Transform (DWT) method. The proposed classification mechanism provides higher classification accuracy compared to baseline classification algorithms based on adaptive neuro fuzzy inference system (ANFIS) and artificial neural networks (ANNs), this is achieved by simultaneously improving two objectives: the prediction accuracy and interpretability of the fuzzy rule-based systems. The results highlight that by searching for both optimal parameters and structure of the classifier, the generalisation capability and interpretability are improved.
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Research Interests: Neuroscience, Psychology, Perception, Audiology, Medicine, and 4 moreVision, Migraine, Aura, and Migraine With Aura
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Research Interests: Psychology, Perception, Visual perception, Adolescent, Medicine, and 15 moreAccommodation, Vision, Humans, Judgment, Female, Male, Contrast sensitivity, Spatial Frequency, Adult, Analysis of Variance, Harmonics, Luminance, photic stimulation, Psychology and Cognitive Sciences, and Medical and Health Sciences
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Although being one of the most common neurological disorders, migraine is commonly misunderstood and misdiagnosed. Current treatments rely on pharmacological approaches, which have been shown not to be effective for all, and so... more
Although being one of the most common neurological disorders, migraine is commonly misunderstood and misdiagnosed. Current treatments rely on pharmacological approaches, which have been shown not to be effective for all, and so alternative, non-invasive treatments are being sought. Transcranial stimulation could be a possible treatment for migraine. Transcranial electrical stimulation generally involves applying a current to the cortex via the scalp. Whilst this has previously been mostly done in clinical settings, the advance of technology means that devices intended for use in the home are becoming more readily available. However, one of the major drawbacks is that we are not sure about the mode of action of transcranial electrical neurostimulation specifically in the case of migraine. The purpose of this review is to consolidate our current understanding of how these methods are thought to work in the case of migraine, considering not only their effectiveness in attempting to tre...
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<p>This code uses a simple model of the primary visual cortex to model the responses of this area to uncomfortable visual stimuli.</p
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Migraine is associated with differences in visual perception, specifically, deficits in the perception of motion. Migraine groups commonly show poorer performance (higher thresholds) on global motion tasks compared to control groups.... more
Migraine is associated with differences in visual perception, specifically, deficits in the perception of motion. Migraine groups commonly show poorer performance (higher thresholds) on global motion tasks compared to control groups. Successful performance on a global motion task depends on several factors, including integrating signals over time. A “motion streak” task was used to investigate specifically integration over time in migraine and control groups. The motion streak effect depends on the integration of a moving point over time to create the illusion of a line, or “streak”. There was evidence of a slower optimum speed for eliciting the motion streak effect in migraine compared to control groups, suggesting temporal integration is different in migraine. In addition, performance on the motion streak task showed a relationship with headache frequency.
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Rapid, continuous gambling formats are associated with higher risks for gambling-related harm in terms of excessive monetary and time expenditure. The current study investigated the effect on gambling response latency and persistence, of... more
Rapid, continuous gambling formats are associated with higher risks for gambling-related harm in terms of excessive monetary and time expenditure. The current study investigated the effect on gambling response latency and persistence, of a new form of within-game intervention that required players to actively engage in response inhibition via monitoring for stop signals. Seventy-four experienced electronic gaming machine gamblers, with a mean age of 35.28 years, were recruited to participate in a rapid, continuous gambling task where real money could be won and lost. Participants were randomly allocated to either the control condition where no intervention was presented, or either a condition with a passive three minute break in play or a condition with a three minute intervention that required participants to engage in response inhibition. Although there was no main effect for experimental condition on gambling persistence, both interventions were effective in elevating response la...
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Action video game players (AVGPs) show enhanced visual perceptual functions compared to their non-video game playing peers (NVGPs). Whether AVGPs are more susceptible towards static contrast motion illusions, such as Fraser Wilcox... more
Action video game players (AVGPs) show enhanced visual perceptual functions compared to their non-video game playing peers (NVGPs). Whether AVGPs are more susceptible towards static contrast motion illusions, such as Fraser Wilcox illusions, has not been addressed so far. Based on their improved perceptual skills, AVGPs are expected to be more susceptible to the illusions and perceive more motion in them. The experience of illusory self-motion (vection) is believed to be dependent on top-down attentional processes; AVGPs should therefore experience stronger vection compared to NVGPs based on their improved attentional skills. Lastly, due to their extensive prior experience with virtual environments, AVGPs should experience less discomfort in VR compared to NVGPs. We presented rotating and expanding motion illusions in a virtual environment and asked 22 AVGPs and 21 NVGPs to indicate the strength of illusory motion, as well as the level of discomfort and vection experienced when expo...
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The limited luminance range of traditional displays means that their visibility is compromised under bright ambient lighting conditions. One solution has been to increase the contrast range and overall luminance of displays. We... more
The limited luminance range of traditional displays means that their visibility is compromised under bright ambient lighting conditions. One solution has been to increase the contrast range and overall luminance of displays. We investigated the effect of exploiting the increased available luminance range in high-bright displays on the viewing experience, in terms of both clarity and comfort. Participants were asked to rate the clarity and comfort of photographs, text, and square- wave gratings, under a range of luminance levels and contrasts. Increasing contrast increased the comfort and clarity of photographs and text. For square-wave gratings increasing contrast increased clarity but decreased comfort. These results suggest that exploiting the full dynamic range of high-bright displays creates clearer and more comfortable results, provided that the images are designed so as not to be inherently uncomfortable.
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Designing a robust classification mechanism with a higher accuracy for Electroencephalogram (EEG) signals is a challenging task. In this paper, a metaheuristic based multi-objective fuzzy modelling mechanism based on the One-Against-One... more
Designing a robust classification mechanism with a higher accuracy for Electroencephalogram (EEG) signals is a challenging task. In this paper, a metaheuristic based multi-objective fuzzy modelling mechanism based on the One-Against-One (OAO) strategy has been developed for classification of multiclass steady state visual evoked potential (SSVEP) data. In this work, three different flickering frequencies in 10Hz, 14Hz and 21Hz were used to elicit the SSVEPs. The recorded EEG signals were segmented into 2.5-second long epochs and features were extracted using the Discrete Wavelet Transform (DWT) method. The proposed classification mechanism provides higher classification accuracy compared to baseline classification algorithms based on adaptive neuro fuzzy inference system (ANFIS) and artificial neural networks (ANNs), this is achieved by simultaneously improving two objectives: the prediction accuracy and interpretability of the fuzzy rule-based systems. The results highlight that by...
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Individuals with migraine show differences in visual perception compared to control groups. It has been suggested that differences in lateral interactions between neurons might account for some of these differences. This study seeks to... more
Individuals with migraine show differences in visual perception compared to control groups. It has been suggested that differences in lateral interactions between neurons might account for some of these differences. This study seeks to further establish the strength and spatial extent of excitatory and inhibitory interactions in migraine-with-aura using a classic lateral masking task. Observers indicated which of two intervals contained a centrally presented, vertical Gabor target of varying contrast. In separate blocks of trials, the target was presented alone or was flanked by two additional collinear, high contrast Gabors. Flanker distances varied between 1 and 12 wavelengths of the Gabor stimuli. Overall, contrast thresholds for the migraine group were lower than those in the control group. There was no difference in the degree of lateral interaction in the migraine group. These results are consistent with the previous work showing enhanced contrast sensitivity in migraine-with-...
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Visual discomfort is the adverse sensations, such as headaches and eyestrain, encountered on viewing certain stimuli. These sensations can arise under certain viewing conditions, such as stereoscopic viewing and prolonged reading of text... more
Visual discomfort is the adverse sensations, such as headaches and eyestrain, encountered on viewing certain stimuli. These sensations can arise under certain viewing conditions, such as stereoscopic viewing and prolonged reading of text patterns. Also, discomfort can occur as a result of viewing stimuli with certain spatial properties, including stripes and filtered noise patterns of particular spatial frequency. This thesis is an exploration of the stimulus properties causing discomfort, within the framework of two theoretical explanations. Both of the explanations relate to the stimuli being difficult for the visual system to process. The first is concerned with discomfort being the result of inefficient neural processing. Neural activity requires energy to process information, and stimuli that demand a lot of energy to be processed might be uncomfortable. The second explanation revolves around uncomfortable stimuli not being effective in driving the accommodative (focussing) res...
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Individuals with migraine aura show differences in visual perception compared to control groups. Measures of contrast sensitivity have suggested that people with migraine aura are less able to exclude external visual noise, and that this... more
Individuals with migraine aura show differences in visual perception compared to control groups. Measures of contrast sensitivity have suggested that people with migraine aura are less able to exclude external visual noise, and that this relates to higher variability in neural processing. The current study compared contrast sensitivity in migraine with aura and control groups for narrow-band grating stimuli at 2 and 8 cycles/degree, masked by Gaussian white noise. We predicted that contrast sensitivity would be lower in the migraine with aura group at high noise levels. Contrast sensitivity was higher for the low spatial frequency stimuli, and decreased with the strength of the masking noise. We did not, however, find any evidence of reduced contrast sensitivity associated with migraine with aura. We propose alternative methods as a more targeted assessment of the role of neural noise and excitability as contributing factors to migraine aura.
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This review describes the subjective experience of visual aura in migraine, outlines theoretical models of this phenomenon, and explores how these may be linked to neurochemical, electrophysiological, and psychophysical differences in... more
This review describes the subjective experience of visual aura in migraine, outlines theoretical models of this phenomenon, and explores how these may be linked to neurochemical, electrophysiological, and psychophysical differences in sensory processing that have been reported in migraine with aura. Reaction–diffusion models have been used to model the hallucinations thought to arise from cortical spreading depolarisation and depression in migraine aura. One aim of this review is to make the underlying principles of these models accessible to a general readership. Cortical spreading depolarisation and depression in these models depends on the balance of the diffusion rate between excitation and inhibition and the occurrence of a large spike in activity to initiate spontaneous pattern formation. We review experimental evidence, including recordings of brain activity made during the aura and attack phase, self-reported triggers of migraine, and psychophysical studies of visual process...
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There is evidence that high-frequency transcranial random noise stimulation (hf-tRNS) is effective in improving behavioural performance in several visual tasks. However, so far there has been limited research into the spatial and temporal... more
There is evidence that high-frequency transcranial random noise stimulation (hf-tRNS) is effective in improving behavioural performance in several visual tasks. However, so far there has been limited research into the spatial and temporal characteristics of hf-tRNS-induced facilitatory effects. In the present study, electroencephalogram (EEG) was used to investigate the spatial and temporal dynamics of cortical activity modulated by offline hf-tRNS on performance on a motion direction discrimination task. We used EEG to measure the amplitude of motion-related VEPs over the parieto-occipital cortex, as well as oscillatory power spectral density (PSD) at rest. A time–frequency decomposition analysis was also performed to investigate the shift in event-related spectral perturbation (ERSP) in response to the motion stimuli between the pre- and post-stimulation period. The results showed that the accuracy of the motion direction discrimination task was not modulated by offline hf-tRNS. A...
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Gaming using VR headsets is becoming increasingly popular; however, these displays can cause VR sickness. To investigate the effects of gender and gamer type on VR sickness motion illusions are used as stimuli, being a novel method of... more
Gaming using VR headsets is becoming increasingly popular; however, these displays can cause VR sickness. To investigate the effects of gender and gamer type on VR sickness motion illusions are used as stimuli, being a novel method of inducing the perception of motion whilst minimising the "accommodation vergence conflict". Females and those who do not play action games experienced more severe VR sickness symptoms compared to males and experienced action gamers. The interaction of the gender and gamer type revealed that prior video gaming experience was beneficial for females, however, for males, it did not show the same positive effects.
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Virtual Reality (VR) experienced through head-mounted displays often leads to vection, discomfort and sway in the user. This study investigated the effect of motion direction and eccentricity on these three phenomena using optic flow... more
Virtual Reality (VR) experienced through head-mounted displays often leads to vection, discomfort and sway in the user. This study investigated the effect of motion direction and eccentricity on these three phenomena using optic flow patterns displayed using the Valve Index. Visual motion stimuli were presented in the centre, periphery or far periphery and moved either in depth (back and forth) or laterally (left and right). Overall vection was stronger for motion in depth compared to lateral motion. Additionally, eccentricity primarily affected stimuli moving in depth with stronger vection for more peripherally presented motion patterns compared to more central ones. Motion direction affected the various aspects of VR sickness differently and modulated the effect of eccentricity on VR sickness. For stimuli moving in depth far peripheral presentation caused more discomfort, whereas for lateral motion the central stimuli caused more discomfort. Stimuli moving in depth led to more hea...
Research Interests: Medicine and Multisensory
It has been suggested that aesthetically pleasing stimuli are processed efficiently by the visual system, whereas uncomfortable stimuli are processed inefficiently. This study consists of a series of three experiments investigating this... more
It has been suggested that aesthetically pleasing stimuli are processed efficiently by the visual system, whereas uncomfortable stimuli are processed inefficiently. This study consists of a series of three experiments investigating this idea using a range of images of abstract artworks, photographs of natural scenes, and computer-generated stimuli previously shown to be uncomfortable. Subjective judgements, and neural correlates were measured using EEG (steady-state visual evoked potentials, SSVEPs). In addition, global image statistics (contrast, Fourier amplitude spectral slope and fractal dimension) were taken into account. When effects of physical image contrast were controlled, fractal dimension predicted discomfort judgements, suggesting the SSVEP response is more likely to be influenced by distribution of edges than the spectral slope. Importantly, when effects of physical contrast and fractal dimension were accounted for using linear mixed effects modelling, SSVEP responses predicted subjective judgements of images. Specifically, when stimuli were not matched for perceived contrast, there was a positive relationship between SSVEP responses and how pleasing a stimulus was judged to be, and conversely a negative relationship between discomfort and SSVEP response. This is significant as it shows that the neural responses in early visual areas contribute to the subjective (un)pleasantness of images, although the results of this study do not provide clear support for the theory of efficient coding as the cause of perceived pleasantness or discomfort of images, and so other explanations need to be considered.
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Migraine is a common neurological disorder with strong links to vision. Interictal migraine is thought to be characterised by internal noise in the brain, possibly due to increased variability in neural firing, which can be estimated... more
Migraine is a common neurological disorder with strong links to vision. Interictal migraine is thought to be characterised by internal noise in the brain, possibly due to increased variability in neural firing, which can be estimated using equivalent noise tasks. High-frequency transcranial random noise stimulation (hf-tRNS) can be used to modulate levels of internal noise in the brain, and so presents a possible therapy to redress noise levels in the migraine brain. This is a case-control study using a 2-alternative forced choice (2AFC) design. hf-tRNS and Sham control stimulation were used alongside a global motion direction discrimination task and visually based equivalent noise tasks. The migraine group demonstrated increased baseline internal noise levels compared to the control group. Internal noise levels, and sampling, were reduced using hf-tRNS but not Sham stimulation. However, there were no differences in terms of coherence thresholds, slopes, and lapse rate for global motion discrimination between the two groups. This is the first demonstration of the possibility of decreasing internal noise levels in migraine using hf-tRNS. Future work could explore the possibility of neurostimulation as a therapy for migraine.
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ABSTRACT The idea of efficient coding in the visual brain allows for predictions for the processing of various types of images, including certain artworks, natural images and uncomfortable images. Efficient processing is thought to result... more
ABSTRACT The idea of efficient coding in the visual brain allows for predictions for the processing of various types of images, including certain artworks, natural images and uncomfortable images. Efficient processing is thought to result in lower responses compared to less efficient processing. The efficiency of the processing is suggested to depend on the architecture of the visual system and the properties of the input image. In this study, neural responses were estimated using EEG across the categories of a set of five images of abstract artworks, a set of five photographs of natural images and a set of five computer-generated uncomfortable images. EEG responses to contrast-matched images were found to be lower for the set of five abstract artworks used in the study compared to the set of photographs of natural images, lending preliminary support for the idea that certain abstract artworks, for example the work of Pollock, may be processed efficiently.
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Certain striped patterns can induce illusory motion, such as those used in op-art. The visual system and the vestibular system work together closely, and so it is possible that illusory motion from a visual stimulus can result in... more
Certain striped patterns can induce illusory motion, such as those used in op-art. The visual system and the vestibular system work together closely, and so it is possible that illusory motion from a visual stimulus can result in uncertainty in the vestibular system. This increased uncertainty may be measureable in terms of the magnitude of head movements. Head movements were measured using a head-mounted visual display. Results showed that stimuli associated with illusory motion also seem to induce greater head movements when compared to similar stimuli. Individuals with migraine are more susceptible to visual discomfort, and this includes illusory motion from striped stimuli. However, there was no evidence of increased effect of illusory motion on those with migraine compared to those without, suggesting that while motion illusions may affect discomfort judgements, this is not limited to only those with migraine.
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Migraine groups show differences in motion perception compared with controls, when tested in between migraine attacks (interictally). This is thought to be due to an increased susceptibility to stimulus degradation (multiplicative... more
Migraine groups show differences in motion perception compared with controls, when tested in between migraine attacks (interictally). This is thought to be due to an increased susceptibility to stimulus degradation (multiplicative internal noise). Fluctuations in alpha-band oscillations are thought to regulate visual perception, and so differences could provide a mechanism for the increased multiplicative noise seen in migraine. The aim of this article was to characterise resting-state alpha-band oscillations (between 8 and 12 Hz) in the visual areas of the brain in migraine and control groups. Alpha-band activity in the resting state (with eyes closed) was recorded before and after a visual psychophysics task to estimate equivalent noise, specifically a contrast detection task. The lower alpha-band (8 to 10 Hz) resting-state alpha-band power was increased in the migraine compared with the control group, which may provide a mechanism for increased multiplicative noise. In agreement ...