Researchers have discovered that epileptic brains are more ordered than non-epileptic ones and also that certain flicking colors seem more likely to cause fits.
In 1997, more than seven hundred children in Japan reportedly suffered an epileptic attack while watching an episode of a popular cartoon. This was later diagnosed as a case of photosensitive epilepsy (a kind of epilepsy caused by visual stimulus) triggered by a specific segment of the cartoon containing a colorful flickering stimulus. Recently in 2007, the animated video footage promoting the 2012 London Olympics faced similar complaint from some viewers.
Because of the widespread usages of television and video games, it is important to detect the crucial visual parameters in triggering an epileptic attack. Common guidelines are available on specific visual parameters of the stimuli like spatial/temporal frequency, stimulus contrast, patterns etc. However, despite the ubiquitous presence of colorful displays and materials, very little is known about the relationship between color-combinations (chromaticity) and photosensitivity. Further it is also not precisely known how the patients' brain responses differ from healthy brains against such colorful stimuli.
In a study published in the journal PLoS ONE on September 25, researchers led by Joydeep Bhattacharya at Goldsmiths, University of London, investigated brain rhythms of photosensitivity against combinational chromatic flickering in nine adult controls, an unmedicated patient suffering from photosensitive epilepsy, two age-matched controls, and another medicated patient.
Their results show that when perturbed by potentially epileptic-triggering stimulus, healthy human brain manages to maintain a non-deterministic, possibly a chaotic state with a high degree of disorder, but an epileptic brain represents a highly ordered state which making it prone to hyper-excitation. Further their study has found how complexities underlying brain dynamics could be modulated by certain color combinations more than the other, for example, red-blue flickering stimulus causes larger cortical excitation than red-green or blue-green stimulus.
Dr. Bhattacharya said, "These findings support the 'decomplexification hypothesis': a healthy brain is more 'complex' than a pathological brain."
However, he added, "It is important to extend the research with larger number of patients to find at what extent these statistical and complexity measures applied in the present paper would have diagnostic potential."
Other researchers in the team are Mayank Bhagat, Chitresh Bhushan, Goutam Saha from the Indian Institute of Technology (Kharagpur, India), Katsumi Watanabe from the University of Tokyo, and Shinsuke Shimojo from the California Institute of Technology.
- Bhagat M, Bhushan C, Saha G, Shimjo S, Watanabe K, et al. Investigating Neuromagnetic Brain Responses against Chromatic Flickering Stimuli by Wavelet Entropies. PLoS ONE, 2009; 4(9): e7173 DOI: 10.1371/journal.pone.0007173
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