When she finished playing a video game for the afternoon, she did not remember the activity - but when she closed her eyes that night, she observed small shapes that moved down a screen and settled into positions.
A Game That Shouldn't Linger
In a study by Robert Stickgold, who investigates sleep at Harvard Medical School, this event occurred. For this experiment, his team instructed college students and multiple individuals with amnesia to play Tetris - this video game requires players to fit falling blocks into horizontal rows. By waking the participants many times during their first hour of sleep, the researchers asked them what they had just experienced. To the researchers, most people described the same visual events regardless of their ability to retain recent information. They saw small geometric pieces that fell and rotated as they attempted to finish a line. And yet no one talked about the keyboard. There were no mentions of the game score, the seating or the scientist who stood nearby to record data. Only the shapes were present in their reports.
The common assumption is that dreaming about an event requires remembering it. If there is no memory, there is no content for dreams. Three out of the five patients with amnesia in the study reported the same images of falling shapes - those individuals had verified damage to the hippocampus, which is the brain region that allows for the creation of new conscious memories. Because of this condition, Tetris should not have remained in their thoughts while they were awake or asleep. On account of those findings, researchers concluded that the hippocampus is not the source of the images that appear at the beginning of sleep.
Two Systems, One Mind
In the cortex those patterns exist in a location that is separate from the areas for daily recall. As the outer layer of the brain, the cortex is where long-term storage and sensory processing are active, rather than the systems for remembering recent meals.
To the researchers, the brain appears to operate at least two distinct systems simultaneously. For one system the primary function is the management of memories that individuals can describe with words, like names, events or the activity of moving blocks into rows. By contrast the other system repeats raw sensory data in an automatic way. It connects this data into unusual images that lack words and appear when a person is close to sleep. There is no requirement for the first system to receive a copy of this information for the images to occur.
A Mountain, Not a Motive
Due to a couple of accounts describing how this research began, it is noted that Stickgold first observed this result after he climbed a mountain. When he was falling asleep that night, he felt the physical sensation of rock beneath his fingers and he was apparently able to create this sensation again through intentional effort. If an ethics board reviewed a study about mountain climbing, they would not provide approval for the risks involved. To solve this, someone proposed that Tetris was a better option because it is a repetitive task that scientists can monitor in a laboratory. Because this information is from later recollections instead of the primary published study, it is necessary to treat the detail as uncertain.
Hijacking the Replay
On later occasions, some researchers investigated whether it was possible to direct this replay system for specific goals. They used games like Tetris to stop the development of memories that cause distress after difficult events. And they attempted to lower strong desires - filling the visual processing areas that the desires require to function.
To describe the concept, both situations share a common goal - if the brain repeats events that are recent and clear in a cycle, researchers might direct that cycle toward productive outcomes rather than allowing it to function without intervention.
Watching Was Enough
In a separate study involving a different video game, investigators observed a result that is difficult to clarify. People who did not interact with the input device but only observed another individual participate experienced visual patterns from the simulation during the transition to sleep - those individuals reported the images at almost the same rate as active participants. As of now there is no complete explanation for this result. For the brain to repeat experiences during the onset of rest, physical interaction is not a requirement. It is only necessary for the visual system to receive the information.