Researched by Haydn Farrelly, Dr Helen Nuttall
and Dr Jason Braithwaite
Click here to participate in this study!
The various regions and circuits in our brains are busy all the time, generating billions of action potentials per second. However, there are meaningful differences in just how active each of our brains are at any given moment dependent on a range of things such as hormonal fluctuations, prescribed medications, and even how much sleep we’ve had the night before. Part of this is also due to our brain’s individual level of cortical hyperexcitability, which can be thought of as the level of ‘background chatter’ going on within the neurons.
When cortical hyperexcitability becomes elevated to an unusual degree in the areas of our brains related to the senses (sight, hearing), this has been attributed to the occurrence of aberrant sensory experiences such as hallucinations. This is particularly important area of study for conditions such as schizophrenia, migraine, and temporal lobe epilepsy, where these experiences can be debilitating.
We have begun to investigate whether part of this may be due to an excess of ‘sensory cross-talk’. This means that in people who have this property of cortical hyperexcitability, the part of the brain related to processing sounds might be more connected to the area of the brain related to processing vision (and vice versa). Therefore, they create a loop where they amplify each other’s level of ‘background chatter’.
To investigate this, we have created an adaptation of the Pattern Glare test. Here, irritating visual stimuli cause an increase of cortical hyperexcitability in visual areas of the brain, leading to hallucinations of shapes and colours which aren’t really there. We have combined our adapted Pattern Glare test with irritating auditory stimuli to see whether the addition of sound can increase the intensity of hallucinations people report due to this sensory cross-talk. The results of this study will advance our understanding of how hallucinations occur in the brain, and inform future studies on the underlying pathology of conditions where these hallucinations can be debilitating.