By Emma Young
If you have healthy vision, there will be a specific region of your brain (in the visual cortex) that responds most strongly whenever you look at faces, and similar regions that are especially responsive to the sight of words or natural scenes. What’s more, in any two people, these face, word and scene regions are located in pretty much the same spot in the brain. However, there is not a specific region for every possible category of visible stimulus – there are no “car” or “shoe” regions, for example (at least, not that have been identified to date). Is that because childhood experience is critical for training the visual cortex – we spend a lot of time looking at faces, say, but not cars? And, if so, in theory, could a lot of childhood time spent looking at a different type of object generate its own dedicated, individual category region?
The answer is “yes”, at least according to an ingenious study, published in Nature Human Behaviour, of people who played a Pokémon game for years of their childhood.
Jesse Gomez led the new study while a graduate student at Stanford University. He was looking for a way to test whether there’s a critical developmental window for the formation of dedicated category regions in the human visual cortex, just as there is in macaque monkeys. He needed a kind of visual stimulus that some adults had been exposed to intensively in childhood but others had not. He thought of how, from about the age of six, he, like many other kids he knew, used to spend countless hours playing a game on his Nintendo Game Boy called Pokémon Red and Blue. It involved identifying hundreds of different Pokémon characters, which look a bit like animals or mythical beasts.
Gomez realised that if he could find other people who had also started playing the game intensively at about the same age, using the same device, he could explore whether this had influenced the organisation of their visual cortex.
He managed to recruit 11 such adults (including himself), and scanned their brains while they were shown images of Pokémon characters, as well as other things, such as faces, corridors and cartoons. Gomez and his colleagues found that within the visual cortex (in the ventral temporal region) of the Pokémon experts, there was a discrete area that was most active when looking at the Pokémon characters. There was no such region in a control group of non-players.
Other work has found that the brains of people who become experts at recognising a type of object (like cars) as an adult respond differently to those objects than the brains of novices. But these differences are not in the visual cortex; they’re more often in the prefrontal cortex, which is involved in attention and decision-making rather than basic visual processing.
Building on the work showing the plasticity of the visual cortex in young macaques, “the current finding of a Pokémon-preferring brain region really drives home just how amazing the plasticity of our developing visual system is,” write Daniel Janini and Talia Konkle of Harvard University in a news comment on the paper, published in the same issue.
Gomez and his colleagues also found that – as with face-processing or word-processing regions – the “Pokemon region” shared a similar location in all of the experts’ brains. They think that the physical size of an object’s image on the retina is important in determining where, in the brain, the category region forms. The image size of a Pokémon character viewed on an old Game Boy screen by children is consistently smaller than that of someone’s face – and a lot smaller than that of a landscape, for instance – which could have a lasting effect on the way visual representations are handled in the adult brain, the researchers think.
As well as being fascinating, the study has potentially important practical implications. “Our data raise the possibility that if people do not share common visual experiences of a stimulus during childhood, either from disease, as is the case in cataracts, or cultural differences in viewing patterns, then an atypical or unique representation of that stimulus may result in adulthood, which has important implications for learning disabilities and social disabilities,” the researchers write.
Consider autism, for example, which is associated with difficulties recognising faces and an aversion to eye contact. If kids with autism grow up looking at faces differently from how most children do, perhaps this explains the observed deficits in the function of the face-sensitive region of their visual cortex, and in turn this could contribute to the social difficulties that autistic children experience. If this account is correct, then finding out how long the window of visual cortical plasticity lasts will be critical for designing effective interventions for autism and other neurodevelopmental conditions.
Image: Pokemon’s figures are on display during the International Tokyo Toy Show 2009 (Photo by Junko Kimura/Getty Images)