Tetris Blocks Fell Behind the Eyelids of Patients Who Forgot Playing
The Tetris effect is the replay of a recent activity as images at sleep onset, and in a 2000 Science study it survived even in amnesia.
Picture a patient with severe damage to the brain’s memory machinery, drifting off in a lab bed. Hours earlier she played a game she cannot remember playing. Now, in this composite of what the study’s amnesic patients reported, she sees blocks falling.
The study (Stickgold, Malia, Maguire, Roddenberry and O’Connor) had 27 participants: 12 novices, 10 experts and 5 amnesic patients with extensive damage to the medial temporal lobes. Nine of the 12 novices reported Tetris imagery. So did three of the five amnesic patients, who could not recall playing.
The Tetris effect is the replay of a recently practiced activity as vivid images at sleep onset, one kind of hypnagogia (its waking-side mirror is explained here). Stickgold and colleagues showed in Science in 2000 that it happens even in people who cannot recall the practice.
Three of five is 60 percent, against 75 percent for novices (9 divided by 12). With groups this small, the gap could be noise.
What does the amnesic result imply?
The usual assumption was that these images were a readout of episodic memory: you remember playing, so you see playing. The patients broke that. They could not retrieve the afternoon, yet something that does not need retrieval kept the afternoon moving.
Read plainly, whatever produces the images does not depend on recall.
Why the blocks, and not the table or the lab coat? Nobody knows. The authors concluded only that such imagery can arise without much help from declarative memory, the kind that stores facts and events you can recall.
The falling-asleep window is also when a sudden full-body jolt tends to strike. The images suggest the practice is still being processed even when the memory of it is gone.