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Removal of epileptogenic sequences from video material

The role of color

From Dutch Epilepsy Clinics Foundation (Drs. Parra and Kalitzin, and E. Dekker and C. de Wit), "Meer en Bosch," Heemstede; Department of Neurology (Dr. Stroink), St. Elisabeth Hospital, Tilburg; and Section Neurobiology (Dr. Lopes da Silva), Swammerdam Institute for Life Sciences, University of Amsterdam, The Netherlands.

Address correspondence and reprint requests to Dr. Jaime Parra, Dept. of Clinical Neurophysiology, SEIN, "Meer en Bosch," Achterweg 5, 2103 SW Heemstede, The Netherlands; e-mail: jparra{at}sein.nl

Background: After Pokémon viewing triggered an epidemic of seizures in Japan, many efforts have been made to design safety guidelines and systems to protect subjects with photosensitivity. The authors developed a new method based upon nonlinear diffusion techniques capable of filtering the epileptogenic content of a video sequence related to color without altering its spatial and luminance content.

Methods: The authors showed to 25 photosensitive patients (18 women, mean age: 22 years) the original Pokémon sequence and a modified one in an ABBA protocol using two television (TV) sets (100 and 50 Hz).

Results: Twenty-three patients had a photoparoxysmal response (PPR) according to Waltz classification with at least one of the scenes. The modified sequence triggered fewer and less severe PPRs than the original version in both TVs (p < 0.001). Original sequences elicited generalized PPRs in 56.5% of the trials for the 50 Hz TV and in 41.3% for the 100 Hz TV, whereas modified sequences elicited these responses in only 8.7% (50 Hz) and 4.3% (100 Hz TV) of the trials (p < 0.001). Sensitivity to the modified version on the 50 Hz TV correlated with pattern sensitivity (p < 0.05).

Conclusion: Specific manipulations of the color modulation-depth could be enough to decrease dramatically the risk of triggering seizures in susceptible subjects exposed to provocative visual scenes. This new method can be implemented in protective devices able to filter out the epileptogenic video sequences in which color plays a fundamental role while leaving intact the spatial content, frequency, and average luminance.

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