Current Study
A simple behavioral tool to identify sensoryhyperexcitability is the Pattern Glare Test (PGT; Wilkins &
Evans, 2001). Participants report visual illusions and sensationsdetected in static spatial gratings. Typical reports include illusory
colors, stripes bending, moving, disappearing, blurring, andsensations of visual discomfort, such as pain and nausea (Evans
& Stevenson, 2008; Wilkins et al., 1984). Higher numbers of
illusions are reported when viewing the mid-range spatial frequency
grating pattern, compared to the lower or high spatial frequency
pattern, due to our visual systems being maximally sensitive between
1-5cpd (Campbell & Robson, 1968). Mid-range spatial frequencies tend to
evoke a large metabolic response in the visual cortex that is even
larger in those who are visually sensitive (Coutts et al., 2012; Huang
et al., 2003). Certain clinical conditions such as those with migraine,
stroke, autism, or synesthesia report higher numbers of illusions in the
PGT and are all associated with a hyper-excitable cortex (Beasley &
Davies, 2012; Fong et al., 2019, 2020; Harle et al., 2006; Ward et al.,
2017). As a result, the illusions (i.e., visual perceptual distortions
and sensations) induced by the PGT are thought to be due to excess
cortical excitation in early visual cortex that spreads to neighboring
parts of the cortex, creating the perception of illusions (Bargary et
al., 2015; Evans & Stevenson, 2008). The relationship between the PGT
and cortical hyperexcitability is so strong that the PGT is now being
used to identify cortical hyperexcitability in other conditions such as
major depressive disorder (Qi et al., 2019) and out-of-body experiences
(Braithwaite et al., 2013). These illusions are not to be confused with
visual hallucinations that manifest in the absence of external stimuli
(Spencer & McCarley, 2005; Teeple et al., 2009).
Here, we used the PGT to test for behavioral evidence ofhyperexcitability as a function of schizotypy symptomatology in thenon-clinical population. Schizotypy refers to individuals
in the general population that vary in schizotypal traits (Broyd et
al., 2016; González-RodrĂguez et al., 2021; Kwapil & Barrantes-Vidal,
2015). The non-clinical population is appealing because it avoids
concerns related to the effects of antipsychotic medications (see
Ettinger et al., 2015 for review; Kelemen et al., 2013), high schizotypy
individuals have similar sensory profiles to SSD (Broyd et al., 2016;
Moussa-Tooks et al., 2021; Myles et al., 2017; Nelson et al., 2013), and
they are accessible.
Hyperexcitability predicts that individuals with higher schizotypy
scores should report more illusions. If so, we can then examine whetherthe number of reported illusions loads on one or more factors of
schizotypy symptomatology (e.g., cognitive perceptual, interpersonal,
disorganization). Alternatively, hypore activity would be
associated with reduced reports of illusions as a function of higher
symptomatology. The value of clearer understanding of the pattern of
behavior is to uncover links between anomalous sensory
experiences and potential neural mechanisms in the pursuit of
meaningful biomarkers in the SSD population.