Accessing Cortical Hyperexcitatbility and Its Predisposition Using Two Types of Measurements

Accessing Cortical Hyperexcitatbility and Its Predisposition Using Two Types of Measurements

Flora Zuo

2015

This study aimed to explore in depth about the cortex hyperexcitability. In order to do so, the study will use the pattern glare task and three questionnaires. These three questionnaires include the Cortex Hyperexcitability Index II, Cardiff Anomalous Perceptions scale, and the Multi-Modality Unusual Sensory Experiences Questionnaire. The pattern glare task induces on-spot hallucinations and distortions, while the questionnaires measure the long-term daily unusual sensory experiences one may have experienced. In this study, both the questionnaires and the task measured the same underlying factor, the cortex hyperexcitability. In the sense that it was hypothesized that the predisposition of seizure-like hallucinations and distortions and of daily-based hallucinations and anomalous experiences should be associated in a particular way. The pattern glare task had two blocks in the experiment, one with a blindfold and the other without. They were presented to participants in different orders to counterbalance the order effect. In between the two blocks, the participants answered the three questionnaires. The result of the study showed no significant effect of the blindfold, suggesting that wearing the blindfold for five minutes neither increased the sensitivity of the eyes nor the visual cortex. Most of the relationships between the pattern glare and questionnaires failed to be significant. The investigation on the association between the predispositions of the two types of hallucinations also failed to show any significance, only MUSEQ and pattern glare has a significant correlation. The migraine and migraine with aura groups appeared to be more sensitive to the phosphene phenomena. Their sensitivity, though the results were not significant, could be clearly observed through descriptive statistics. Although the results and findings failed to prove the research hypothesis, probably due to the main limitation of the poorly presented stimuli, the current study to some extent was able to expand the current understanding of cortex hyperexcitability demonstrated by the previous works, and further offered more possibilities for future studies.

Along with the pattern glare task, there were three more questionnaires used in the study, these are MUSEQ (Mitchell et al., 2017), CAPS (Bell et al., 2006), and CHI II (Fong et al., in press). This study has been ethically approved by the Department of Psychology in Lancaster University on 11th May 2018.
Participants
The current study screened participants before they could take part in the experiment, the screening standard is whether they have been diagnosed with photosensitive epilepsy, epilepsy, or that they recently had a brain or eye surgery. This criterion was created as the viewing of the striped pattern of particular spatial frequencies may induce seizures in patients with photosensitive epilepsy (Wilkins et al., 1984).
It turned out none were excluded due to disease or had a history of diseases. There was a total of 43 participants who took part in the study. Among them, 15 were males and 28 were females. The age ranged from 19 to 36, with a standard deviation of 2.92, and around half of the participants were native English speakers. The six participants who self-reported having a migraine or a migraine with aura were noted before the study, as the pattern glare task may induce or intensify their symptoms, which can cause visual discomfort, visual distortions, or a headache. Among the six participants who reported they had migraineur, three of them were migraineurs with aura.
Stimuli and Procedure
The current study used stimuli that were printed onto cards, and the stimuli were presented to the participants from around 50 cm away at eye level. The patterns were the same size at 20mm * 15 mm, all in black and white, and with the shape of the ellipse. According to the given conditions, the visual angle was calculated to be 12.84 degrees. The three questionnaires were all printed on paper, and the participants were asked to read aloud their answers instead of writing it down. The plain black blindfold which participants were asked to wear during the study was bought from the drugstore.
Material
There were three different patterns used in this study, the spatial frequency gratings for these patterns are 11 cpd (cycles-per-degree), 3 cpd, and 0.7 cpd respectively. All the patterns were achromatic, with a fixation dot in the centre of them. After each of the stimulus was presented, there were 17 questions which the participants had to answer. The questions asked about the intensity of the anomalous visual phenomena, the types of visual hallucinations, and whether they have a headache or dizziness after the experiment. The materials were adapted from the previous works of Braithwaite et al. (2014). The three questionnaires in between the two blocks of stimuli presentations were MUSEQ, CAPS, and CHI II. MUSEQ (Mitchell et al., 2017) has 43 items of six factors, including Auditory, Visual, Olfactory, Gustatory, Bodily sensations, and Sensed presence; the measurement is a five-point Likert scale which targets the frequency of USE. CAPS (Bell et al., 2006) has 32 items, also addressing the anomalous experiences from different modalities. For each item, if the participants confirmed that they have had related experiences, they then rated their experiences out of three five-point scales on distress, intrusiveness, and frequency. CHI II has 30 items, and each one will be questioned about its frequency and intensity. The measurement is a seven-point Likert scale, with zero as never or not intense and six as all the time or extremely intense. The questionnaire is the recently updated version of the original CHI, and the 30 items in it can be loaded onto three non-overlapping factors, includes heightened visual sensitivity and discomfort (HVSD), aura-like hallucinatory experience (AHE), and distorted visual perception (DVP).
For the MUSEQ and CAPS, the original unrevised questionnaire was used during the experiments, however, only parts of the answers given was used in the analysis. This decision was made as the data analysis would be too complicated to take all the factors into consideration, especially when they are just partially related to the research question. Therefore, for the MUSEQ questionnaire, only Visual, Auditory, and Bodily modality were analysed, and for CAPs, the primary concern is exclusively about the temporal lobe experience factor.
For the non-blindfold block, all three stimuli were presented; but for the blindfold block, only the medium and high CPD stimuli were included. The low frequency stimulus is excluded because it was too mild to induce any hallucination on the participants. Including it in the blindfold condition is more for its suggestibility; participants who have given a high rating for the low frequency stimulus may produce unreliable scores on the other measures as well (Wilkins et al., 1984). Therefore, participants with too high low PG value would be excluded from the analysis.
Procedure
Prior to the experiment, the participants were asked to sit in a specific spot where the distance between them and the stimuli was fixed at around 50cm. Then they were given the information sheet and consent form, which contained the information they needed to know in order to proceed with the study. On the consent form, there was a list of questions asking about specific medical conditions including epilepsy, photosensitive epilepsy, neuro and eye surgery, and migraine and migraine with aura. The researchers then confirmed that the participants did not suffer or had suffered from those conditions before the experiment could take place.
The first phase of the experiment was the pattern glare test that comprised of two blocks, one with the blindfold and the other without. Participants were labelled with a number which was used as their order of participation. Participants with odd numbers had non-blindfold block first, and the ones with even numbers had blindfold block first. The numbering and manipulation of the block presentation were kept unknown from the participants. The blindfold block contained two stimuli presentation, one was the medium spatial frequency (SF), and the other was the high SF. The reason why the low SF one was not included is that it worked as a control in the non-blindfold block, as there is minor to no effect of this stimulus (Braithwaite et al., 2013, 2015). The blindfold wearing was prior to the presentation of the stimuli; thus, participants wore the blindfold for five minutes before the blindfold block.
After the participants finished viewing each pattern, they would answer the 17 questions about the associated visual distortions. They were asked to read aloud the answers and the answers would be immediately recorded using a computer. There was no break in between each trial, and the participants would keep on viewing the next one once they finished all the questions.
In between the two stimuli present blocks, the participants were asked to finish the three questionnaires: MUSEQ (Mitchell et al., 2017), CAPS (Bell et al., 2006) and CHI II (Braithwaite et al., in press). It takes approximately 20 minutes to complete the three questionnaires. After the questionnaires are completed, the next block of stimuli was presented with a blindfold or no blindfold respectively. After both of the blocks and the three questionnaires were completed, the debrief sheet was given to participants at the end of the experiment.
The entire process took about 30 minutes for a native English speaker, for participants who speak English as their second language, the duration took slightly longer, at around 35 to 40 minutes.

Lancaster University

data/SPSS.sav
data/.JASP

Zuo2015

Ellie Ball

Open

None

English

Data

LA1 4YF

Jason Braithwaite

MSc

Neuropsychology

43 Participants (15 males and 28 females)

ANOVA
Bayesian Analysis
Correlation
t-test