A growing body of research calls into question the idea that most brain areas are tied to specific sensory inputs.
Whether reading the word "orange" in Braille or in English, the same brain area identifies it. The idea that different sensory inputs are necessarily processed in disparate regions may be obsolete.
Does a blind person reading Braille process words in the brain differently than a person who reads by sight? Mainstream neuroscience thinking implies that the answer is yes because different senses take in the information. But a recent study in Current Biology finds that the processing is the same, adding to mounting evidence that using sensory inputs as the basis for understanding the brain may paint an incomplete picture.
Researchers in Israel, Canada and France used brain imaging to observe the neural activity of eight blind subjects as they read Braille. They found that although the blind subjects were using their sense of touch, their brains showed activity in the same so-called visual region that sighted people use when they read.
The finding runs counter to the long-held belief that the functions of areas of the brain are determined by the senses that feed them information. Instead it suggests that at least some areas developed primarily to perform a specific job. “The brain will use any information it can get to achieve this task,” says lead author Amir Amedi of the Hebrew University of Jerusalem. Although his study only dealt with reading, Amedi thinks many areas of the brain are similarly task-oriented. He points to a 2005 study in which researchers found that participants who inspected an object with either their hands or their eyes used the same brain region to ultimately identify it. “When we look at a dog or a hammer and we recognize it, we have a very specific center that is activated,” he says. “It’s the exact same for touching it.”
According to Mary Helen Immordino-Yang, a neuroscientist at the University of Southern California not associated with the reading or touch studies, this task-based view of the brain is becoming widely accepted by cognitive neuroscientists but almost completely ignored by their hard-neuroscience colleagues. Neuroscientists who work on the biology of the brain tend to believe that humans are driven “by how the world pokes us,” she says—in other words, sensory stimuli. They fail to see that “the hallmark of humanity is the ability to move beyond sensory inputs.”
One criticism hard neuroscientists have of this task-based view is that certain cognitive processes are simply too new for humans to have evolved a specific brain area to process them. Reading, for example, has been around for only about 5,000 years. Its invention is much too recent to have had an effect on the evolution of the human brain. So how, then, could there be a part of the brain designated for reading?
Both Immordino-Yang and Amedi agree this is an important question. Immordino-Yang sees the evidence as a testament to the brain’s ability to accommodate human inventions in the modern world. “It’s amazing how plastic our brain is,” she says. Parts of the brain are constantly being co-opted to process technological innovations. Amedi concurs: “We use the best networks that already did something most similar to this task. This is what allows us to evolve.”