Several studies have linked voluntary and excessive online use to depression, poor school performance, increased irritability and more impulsiveness to go online (confounding addicts' efforts, if they want to at all, to stop pouring excessive time into online games). To study the effects of possible Internet addiction on the brain, researchers began with the Young Diagnostic Questionnaire for Internet addiction.
This self-assessment test, created in 1998 by psychiatrist Kimberly Young of Saint Bonaventure University in New York State, is an unofficial standard among Internet addiction researchers, and it consists of eight yes-or-no questions designed to separate online addicts from those who can manage their Internet use. (Questions range from, "Do you use the Internet as a way of escaping from problems or of relieving an anxious mood?" to "Have you taken the risk of losing a significant relationship, job, educational or career opportunity because of the Internet?".)
The China-based research team picked 18 college-age students who satisfied addict criteria, and these subjects said they spent about 10 hours a day, six days a week playing online games. The researchers also selected 18 healthy controls who spent less than two hours a day online (an unusually low number, says von Deneen). All of the subjects were then plopped into an MRI machine to undergo two types of brain scans.
One set of images focused on gray matter at the brain's wrinkled surface, or cortex, where processing of speech, memory, motor control, emotion, sensory and other information occurs. The research team simplified this data using voxel-based morphometry, or VBM—a technique that breaks the brain into 3-D pixels and permits rigorous statistical comparison of brain tissue density among people.
The researchers discovered several small regions in online addicts' brains shrunk, in some cases as much as a 10 to 20 percent. The affected regions included the dorsolateral prefrontal cortex, rostral anterior cingulate cortex, supplementary motor area and parts of the cerebellum.
What's more, the longer the addiction's duration, the more pronounced the tissue reduction. The study's authors suggest this shrinkage could lead to negative effects, such as reduced inhibition of inappropriate behavior and diminished goal orientation.
But imaging neuroscientist Karl Friston of University College London, who helped pioneer the VBM technique, says gray matter shrinkage is not necessarily a bad thing. "The effect is quite extreme, but it's not surprising when you think of the brain as a muscle," says Friston, who was not involved in the study. "Our brains grow wildly until our early teens, then we start pruning and toning areas to work more efficiently. So these areas may just be relevant to being a good online gamer, and were optimized for that."
(Friston says London taxi drivers provide a telling comparative example of the brain's ability to reshape itself with experience. In the 2006 study, researchers compared taxi drivers' brains with those of bus drivers. The former showed increased gray matter density in their posterior hippocampi—a region linked to maplike spatial navigation and memory. That probably comes as no surprise to London cabbies, who spend years memorizing a labyrinthine system of 25,000 streets, whereas bus drivers have set routes.)
As another crucial part of the new study on Internet addiction, the research team zeroed in on tissue deep in the brain called white matter, which links together its various regions. The scans showed increased white matter density in the right parahippocampal gyrus, a spot also tied to memory formation and retrieval. In another spot called the left posterior limb of the internal capsule, which is linked to cognitive and executive functions, white matter density dropped relative to the rest of the brain.