It’s too soon to load Tetris onto the equipment that soldiers carry into battle, but there’s an intriguing hint that playing that geometric game might act as what scientists are calling a “cognitive vaccine” against the horrible flashbacks that characterize post-traumatic stress disorder (PTSD), which more and more of those returning home from Iraq and Afghanistan are suffering.

The idea of using Tetris to vaccinate soldiers against PTSD rests on two facts. One, the brain has a finite processing capacity for each of two kinds of information: sensory/visual/spatial and narrative/meaning. Two, there is a window of about 6 hours to disrupt memory consolidation. What this implies, scientists led by Emily Holmes of the University of Oxford write in a new paper in the open-access journal PLoS One, is that a sufficiently demanding visuospatial task will keep the brain from retaining other spatial/visual information--that is, images, including traumatic ones. Tetris should be such a task, since recognizing the shapes and moving the blocks around places demands on the brain’s spatial-processing channel.

“Visuospatial tasks post-trauma, performed within the time window for memory consolidation,” write the scientists, should “reduce subsequent flashbacks.” But importantly, the narrative and meaning of the events should be unaffected, since that is a separate processing channel: people should remember that they witnessed or experienced a trauma, but should not be besieged by vivid visual images of it.

To test their idea, the scientists had 40 volunteers, aged 18 to 47, watch a 12-minute film showing such traumatic events as graphic scenes of actual surgery, fatal road traffic accidents and drowning. After a 30-minute break, half the volunteers played Tetris for 10 minutes and half did not. The scientists then had them keep a daily diary, noting when they had a flashback to any of the awful images in the film.

The initial results were promising. Playing Tetris soon after viewing the gory film clips reduced the number of flashbacks the volunteers had from just over 6 to about 3. It really did look as if the visuospatial demands of Tetris blocked the consolidation of the traumatic visuospatial memories. (Tetris should not interfere with memories for new facts, but you should probably think twice before playing it right after you tried to memorize a map or something else with a lot of visual or spatial content.)

“This is only a first step in showing that this might be a viable approach to preventing PTSD,” said Holmes. “We wanted to find a way to dampen down flashbacks—that is, the raw sensory images of trauma that are over-represented in the memories of those with PTSD. Tetris may work by competing for the brain’s resources for sensory information. We suggest it specifically interferes with the way sensory memories are laid down in the period after trauma and thus reduces the number of flashbacks.”