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So How Exactly Does a GIF Cause a Seizure?

Scientists can identify the triggers of photosensitive epileptic seizures, like strobes, but working out why these seizures happen is a little harder.
dierk schaefer/Flickr

Very few people will ever have to suffer the terrible effects that strobes and flashing lights have on those diagnosed with photosensitive epilepsy.

But for Newsweek journalist Kurt Eichenwald, who last year suffered from a debilitating photosensitive seizure after viewing a strobing GIF sent by a Twitter troll, the dangers of flashing lights are all too real. "You deserve a seizure for your post," the suspect, John Rayne Rivello, said to Eichenwald, just before he sent the GIF.


This isn't the first time that people diagnosed with photosensitive epilepsy have been maliciously targeted over the internet, though. In 2008 the Epilepsy Foundation had to temporarily shut down its website after hackers plastered the Foundation's forums with flashing images.

In the vast majority of cases, photosensitive epilepsy is a genetic condition that affects just three percent of all of those diagnosed with some form of epilepsy. Recent research, led by scientists at Imperial College London, suggested that an 'epileptic network' of some 320 genes, dubbed M30, is responsible for the condition. When this network malfunctions, epilepsy is triggered, concluded the paper.

But what's the science behind photosensitive seizures? While many of the triggers have been identified and can be avoided, such as the frequency of the flashing lights or the intensity of a light source (two factors that were prominent in the Eichenwald attack), doctors and scientists still poorly understand the actual mechanics of a seizure, according to the Epilepsy Society.

A number of recent medical journals do paint a clearer picture of the effects of light on the brain, however.

In a 2014 study published by the Austin Journal of Clinical Neurology, three Japanese researchers linked strobe lights to eliciting peak regional cerebral blood flow in the visual cortex, which then has a knock on effect on the central nervous system.


"High-temporal-frequency visual stimuli can yield hazardous responses in the central nervous system," explained Masaaki Tanaka, Akira Ishii, and Yasuyoshi Watanabe. The three researchers also linked the increase of oxygenated blood in the cerebral cortex to certain frequencies of flashing light, another contributing factor to seizures.

At the heart of this current research in determining exactly why the brain reacts as it does is a process called Magnetoencephalography (MEG).

Read more: Neuroscientists Uncover More Evidence Linking Epileptic Seizures and Music

MEG works in much the same way as MRI, scanning the brain for electrical currents firing off inside neurons. These electrical currents create magnetic fields that can give researchers valuable information about neural activity, especially when it comes studying the process of a seizure, and for localizing areas of the brain that can benefit from epilepsy surgery.

Using MEG techniques, the Japanese researchers behind the 2014 paper even suggested that seizures may be linked to a system in the central nervous system that is susceptible to certain frequency of vibrations ultimately caused by strobe lighting.

"The existence of a fundamental frequency suggests the presence of a periodic system in the central nervous system," said the researchers. "Every periodic system exhibits some degree of sympathetic vibration. The wind induced structural collapse of Tacoma Narrows Bridge in WA in 1940 is a famous example of the hazardous nature of this type of vibration."

The researchers concluded that strobe light stimuli may indeed affect such a periodic system in the brain, with seizures and other neuropsychological abnormalities acting as the results to such systems being compromised.

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