The cortical hyperexcitability index (CHi): a new measure for quantifying correlates of visually driven cortical hyperexcitability

Introduction
Aberrations of visual experience, including visual hallucinations and visual distortions are known to be associated with increased cortical hyperexcitability. As a consequence, the presence, intensity and frequency of certain experiences may well be indicative of an underlying increase in cortical hyperexcitability.

Method
The current study presents a new proxy measure of cortical hyperexcitability, the Cortical Hyperexcitability Index (CHi). Two-hundred and fifty healthy participants completed the CHi with the results subjected to Exploratory Factor Analysis (EFA).

Results
The EFA revealed a 3-factor model as the most parsimonious solution. The 3 factors were defined as; (i) heightened visual sensitivity and discomfort; (ii) negative aura-type visual aberrations; and, (iii) positive aura-type visual aberrations. The identification of 3-factors suggests that multiple mechanisms underlie the notion of cortical hyperexcitability, providing researchers with new and greater precision in delineating these underlying features.

Conclusion
The factorial structure of the CHi, and the increased precision could aid the interpretation of findings from neuroscientific (i.e., brain-imaging / stimulation) examinations of cortical processes underlying aberrant perceptions across a host of clinical, neurological, and pathological conditions. As a consequence, the CHi is a useful and comprehensive proxy measure of cortical hyperexcitability with considerable scientific and clinical utility.