Dr. Rex Jung and Dr. Richard Haier, co-investigators in the Tetris study, made use of brain imaging and Tetris to see if practice makes the brain efficient because it increases gray matter.
Jung, a clinical neuropsychologist, said: "One of the most surprising findings of brain research in the last five years was that juggling practice increased gray matter in the motor areas of the brain.
"We did our Tetris study to see if mental practice increased cortical thickness, a sign of more gray matter. If it did, it could be an explanation for why previous studies have shown that mental practice increases brain efficiency.
"More gray matter in an area could mean that the area would not need to work as hard during Tetris play."
Haier, lead author of a 1992 research that discovered practicing Tetris led to greater brain efficiency, also added: "We were excited to see cortical thickness differences between the girls that practiced Tetris and those that did not.
"But, it was surprising that these changes were not where we saw more efficiency. How a thicker cortex and increased brain efficiency are related remains a mystery."
The study has been published in the open access journal BMC Research Notes.