“For the Elden Ring, I trained it 429 times to recognize a single activity, me imagining pushing something forward,” she says. Karyal says It takes some effort to produce enough data to effectively train the system to recognize a given behavior. While EEG signals are highly variable, common patterns within them can be recognized and decoded from repeated mental actions. “The pattern of activity my brain happened to consistently make during that task is what the software learned to recognize.”

“I was visualizing pushing something forward in my head,” says Karyal. This technique, known as motor imagery, looks for average patterns of neural activity from a person’s brain while they imagine themselves moving their body in a given repeatable pattern. To convert EEG signals into inputs that the game could recognize, Karyal trained the software to recognize brain-wave patterns she generated while imagining different physical movements. To build the Elden Ring controller, she started with an EEG headset and accompanying software offered by Emotiv, a consumer-neurotech company. When combined with a pair of headset-mounted accelerometers that replace character movement and camera controls, the headset becomes a complete, hands-free game controller. But she has since extended her homemade tech to recognize enough distinct EEG patterns to replace every input she needs to play the game. Karyal has completed the game using early versions of the system, which could produce only a small number of inputs. “I have spent more hours training the EEG than I have in the game, and I have over 250 hours in the game.” -Perri Karyal, Twitch gaming streamer This allows her to control her Elden Ring character–swinging weapons, casting spells, and dodging enemy attacks–by evoking those same patterns in brain activity. Karyal says she designed the system to recognize repeatable patterns in EEG measurements–electrical oscillations recorded from a headset placed on a person’s scalp–and to in turn simulate the act of pressing a button on a game pad or keyboard.

This month, Karyal demonstrated a fully hands-free version of the controller live on her stream. Karyal, who hosts a regular show on, has been using a custom controller that reads electroencephalogram signals (EEG) to play the popular video game Elden Ring since earlier this year. Perri Karyal, a video-game and variety streaming-video broadcaster, has created a way to play games with her brain waves.

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