Extending the Cortical Hyperexcitability Index

Extending the Cortical Hyperexcitability Index

Haydn Farrelly

27/05/2022

Anomalous perceptual experiences are associated with underlying excitation of neural activity in the cerebral cortex, known as cortical hyperexcitability (Wilkins, 1995). This can be measured behaviourally by the pattern glare test, where migraineurs consistently show greater susceptibility to anomalous visual percepts in response to grating patterns than control participants (for review see Evans & Stevenson, 2008). Based on these findings, Fong, Takahashi and Braithwaite (2019) developed a screening measure of visual cortical hyperexcitability, the Cortical Hyperexcitability Index (CHi-II), through exploratory factor analysis. This project aims to create auditory-based items for the CHi-II. We know cortical hyperexcitability in the auditory cortex is also associated with a number of auditory symptoms in migraine such as heightened auditory sensitivity and a range of anomalous auditory percepts, ranging from tinnitus-like tones to multiple conversing voices (Vingen, Pareja & Støren et al., 1998; Miller, Grosberg, Crystal & Robbins, 2015). As such we created seven auditory items through adaptation of related questionnaire items and generating unique items based on phenomenology of patient descriptions; these refer to experiences of hearing voices or unexplained sounds under various circumstances, as well as sensitivity to noise. Exploratory Factor Analysis will be conducted on the CHi-II alongside auditory items to test which factor each item best loads onto, as well as using Cronbach's Alpha to assess internal validity. Results are discussed in terms of the debate on global versus localised effects of patterns of hyperexcitability, as well as implications for our understanding of multisensory anomalous perceptual experiences.

Perceptual Aberrations, Cortical Hyperexcitability, Migraine, Aura, Tinnitus, Auditory Perception, Visual Perception, Hallucinations

Method

Participants

Forty-five participants age 18-24 (M = 19.24) took part either for research credits or without incentive. Of these, thirty-seven (82%) were female and thirty-seven (82%) were right-handed. Prior to the main questionnaire, a pre-screening survey asked participants to declare any history of neurosurgeries (8.22%), neurological conditions (2.22%), psychological conditions (17.78%), ocular conditions (15.56%), epilepsy (0%), migraine (24.44%), or tinnitus (15.56%).



Auditory Item Creation

As with the original CHi-II, items were based on previous questionnaires measuring anomalous perceptual experiences (Sierra & Berrios, 2000; Bell, Halligan & Ellis, 2006) alongside patient reports of auditory experiences in migraine (Miller, Grosberg, Crystal & Robbins, 2015; Vreeburg, Leijten, Sommer & Sommer, 2016). These items were split into two categories: voice-hearing, and noise-hearing. We distinguished between hearing a single voice in item one ‘Do you ever hear a single voice talking aloud in your head without a clear source?’, or multiple voices in item two ‘Do you ever hear 2 or more unexplained voices talking with each other?’, as these are delineated in patient reports (Miller et al., 2015; Vreebrug et al., 2016). We also distinguish between hearing instructing voices in item three ‘Do you ever hear voices telling you what to do?’, and hearing voices which comment on thoughts and actions in item four ‘Do you ever hear voices telling you what to do, or commenting on what you are thinking or doing?’, as suggested by the CAPS and CDS (Sierra & Berrios, 2000; Bell et al., 2006). The first noise item asked participants about the occurrence of anomalous sounds in item five ‘Do you ever notice sounds, such as ringing / buzzing , which other people around you cannot hear?’ as recommended by CAPS and CDS (Sierra & Berrios, 2000; Bell et al., 2006). The final noise items referred to volume of sounds in item six ‘Do you ever become annoyed or agitated by sounds that are too loud or uncomfortable for you?’, and distraction caused by sounds in item seven ‘Do you ever become distracted when surrounded by lots of noise?’ as these are common auditory complaints of migraine sufferers (Miller, Grosberg, Crystal & Robbins, 2015; Vreeburg, Leijten, Sommer & Sommer, 2016). As with the original CHi-II, participants respond to items in terms of their frequency on a zero (‘Never’) to six (‘All the time’) Likert scale, and their intensity on a zero (‘Not at all’) to six (‘Extremely intense’) Likert scale. Scores from these two scales are added to create a total score for each item. Informed consent was obtained from all participants.



Analysis

Total scores were collected from both the original CHi-II questionnaire (Braithwaite, Marchant & Takahashi et al., 2015; Fong, Takahashi & Braithwaite, 2019) and these additional auditory items to complete an EFA. Parallel analysis was also applied to statistically verify the loadings of the new items onto the underlying factor structure (Horn, 1965; Hayton, Allen & Scarpello, 2004). Cronbach’s alpha was used to test the internal consistency of each factor.

Lancaster University

Data/Excel.csv

Farrelly2021

Haydn Farrelly

Open

Braithwaite, Marchant, Takahashi, Dewe & Watson (2015)
Fong, Takahashi & Braithwaite (2019)

English

Data

LA1 4YF

Dr. Jason Braithwaite

MSc

Neuroscience

45

Factor Analysis