Evidence for distinct clusters of diverse anomalous experiences and their selective association with signs of elevated cortical hyperexcitability

Visual cortical hyperexcitability is now known to be an underlying factor for aberrant visual experience, including hallucinations, and pattern or light induced visual discomfort. Such factors have also been observed in neurological and non-clinical groups (albeit in attenuated form) – consistent with the notion of a continuum of anomalous experiences. Utilizing an exploratory factor analysis (EFA) approach (n = 300), Study 1 developed a revised proxy screening measure for visual cortical hyperexcitability – the Cortical Hyperexcitability index – II(CHi-II). The EFA revealed a stable 3-factor solution which can be characterised as; (i) Heightened Visual Sensitivity and Discomfort (HVSD); (ii) Aura-like Hallucinatory Experience (AHE); and, (iii) Distorted Visual Perception (DVP). Study 2 tested both a self-reported migraine group and a control group on the CHi-II in conjunction with a computerised pattern-glare task that is known to reflect visual cortical hyperexcitability. The migraine group produced significantly elevated scores on both the AHE and HVSD factors of the CHi-II, relative to controls. Among the non-migraine group, subjects who scored higher in the pattern-glare task also produced significantly elevated scores on the AHE factor compared to those with low pattern-glare task scores. Collectively, these findings support the utility of the CHi-II as an indirect proxy measure for signs of cortical hyperexcitability and reveal new categorical distinctions for the nature of the anomalous perceptions. These perceptions may well reflect diverse neurocognitive underpinnings leading to advancements in our understanding of aberrations in conscious experience.