Posts tagged parietal lobe
Articles and news from the latest research reports.
Centers throughout the brain work together to make reading possible
A combination of brain scans and reading tests has revealed that several regions in the brain are responsible for allowing humans to read.
The findings open up the possibility that individuals who have difficulty reading may only need additional training for specific parts of the brain — targeted therapies that could more directly address their individual weaknesses.
“Reading is a complex task. No single part of the brain can do all the work,” said Qinghua He, postdoctoral research associate at the USC Brain and Creativity Institute, based at the USC Dornsife College of Letters, Arts and Sciences, and first author of a study on this research that was published in The Journal of Neuroscience on July 31.
The study looked at the correlation between reading ability and brain structure revealed by high-resolution magnetic resonance imaging (MRI) scans of more than 200 participants.
To control for external factors, the participants were about the same age and education level (college students); right-handed (lefties use the opposite hemisphere of their brain for reading); and all had about the same language skills (Chinese-speaking, with English as a second language for more than nine years). Their IQ, response speed and memory were also tested.
The study first collected data for seven different reading tests of a sample of more than 400 participants. These tests were intended to explore three aspects of their reading ability: phonological decoding ability (the ability to sound out printed words); form-sound association (how well participants could make connections between a new word and sound); and naming speed (how quickly participants were able to read out loud).
Each of these aspects, it turned out, was related to the gray matter volume — the amount of neurons — in different parts of the brain.
The MRI analysis showed that phonological decoding ability was strongly connected with gray matter volume in the left superior parietal lobe (around the top/rear of the brain); form-sound association was strongly connected with the hippocampus and cerebellum; and naming speed lit up a variety of locations around the brain.
“Our results strongly suggest that reading consists of unique capacities and is supported by distinct neural systems that are relatively independent of general cognitive abilities,” said Gui Xue, corresponding author of the study. Xue was formerly a research assistant professor at USC and now is a professor and director of the Center for Brain and Learning Sciences at Beijing Normal University.
“Although there is no doubt that reading has to build up existing neural systems due to the short history of written language in human evolution, years of reading experiences might have finely tuned the system to accommodate the specific requirement of a given written system,” Xue said.
He and Xue collaborated with Chunhui Chen and Qi Dong of Beijing Normal University; Chuansheng Chen of the University of California, Irvine; and Zhong-Lin Lu of Ohio State University.
One of the top features of this study was its unusually wide sample size, according to researchers. Typically, MRI studies test a relatively small sample of individuals — perhaps around 20 to 30 — because of the high cost of using the MRI machine. Testing a single individual can cost about $500, depending on the nature of the research.
The team had the good fortune of receiving access to Beijing Normal University’s new MRI center — the BNU Imaging Center for Brain Research — just before it opened to the public. With support from several grants, the researchers were able to conduct MRI tests on 233 individuals.
Next, the group will explore how to combine data from other factors, such as white matter, resting and task functional MRI, as well as more powerful machine-learning techniques, to improve the accuracy of individuals’ reading abilities.
“Research along this line will enable the early diagnosis of reading difficulties and the development of more targeted therapies,” Xue said.
The man who needs to paralyse himself
"I have attempted to break my back, but I missed. I need to be paraplegic, paralysed from the waist down."
Sean O’Connor is a very rational man. But he also tried, unsuccessfully, to sever his spine, and still feels a need to be paralysed.
Sean has body integrity identity disorder (BIID), which causes him to feel that his limbs just don’t belong to his body.
Sean’s legs function correctly and he has full sensation in them, but they feel disconnected from him. “I don’t hate my limbs – they just feel wrong,” he says. “I’m aware that they are as nature designed them to be, but there is an intense discomfort at being able to feel my legs and move them.”
The cause of his disorder has yet to be pinpointed, but it almost certainly stems from a problem in the early development of his brain. “My earliest memories of feeling I should be paralysed go back to when I was 4 or 5 years old,” says Sean.
The first case of BIID was reported in the 18th century, when a French surgeon was held at gunpoint by an Englishman who demanded that one of his legs be removed. The surgeon, against his will, performed the operation. Later, he received a handsome payment from the Englishman, with an accompanying letter of thanks for removing “a limb which put an invincible obstacle to my happiness” (Experimental Brain Research).
We now think that there are at least two forms of BIID. In one, people wish that part of their body were paralysed. Another form causes people to want to have a limb removed. BIID doesn’t have to affect limbs either – there have been anecdotal accounts of people wishing they were blind or deaf.
DIY operations
There are many reported cases of people with BIID attempting to break their back, like Sean, or perform a DIY operation to alleviate their discomfort. Some even pay for surgeons to amputate their healthy limbs. Now the first study of this desperate form of treatment, by Peter Brugger at the University of Zurich, Switzerland, and colleagues, suggests that chopping off a healthy limb “cures” people of this form of BIID. Brugger says they interviewed about 20 people with BIID, many of whom have had an illegal amputation. All said they were satisfied with the outcome.
But the findings, so far unpublished, are tentative and do not justify such a treatment, says Brugger. “We don’t have enough scientific evidence to propose amputation or paralysis. Before we have an understanding of something, we can’t think of developing a treatment.”
Brugger disagrees with the suggestion that the disorder is psychological. “The neurological side of the data is too convincing,” he says. “Why would a vague desire to be handicapped show itself as a precise need to be amputated two centimetres above the knee, for example? I certainly think it’s more a representational deficit in the brain in all cases, than a psychological need for attention.”
The parietal lobe, situated at the top of the brain, is almost certainly involved. It is here that a complex set of brain networks enable us to attach a sense of self to our limbs. In 2011, V. S. Ramachandran, at the University of California, San Diego, and his colleagues examined the brain activity of four people with BIID.
Confusion in the brain
They found significantly reduced activation in the right superior parietal lobe when researchers touched the part of the leg that people wanted amputated, compared with when they touched the part people wanted to keep. The researchers say that this area of the brain is key to creating a “coherent sense of having a body” (Journal of Neurological Neurosurgery and Psychiatry).
The brain hates to be confused, says Ramachandran. So when people with BIID feel the sensation of touch, they can’t incorporate this message into the regions of the brain that identify the limb as being part of themselves. In an attempt to remove the confusion, it seems the brain rejects the limb altogether.
Brugger hypothesises that some people are born with a relative weakness in brain networks which enable us to accept all our limbs as our own. This is usually naturally corrected as they grow up, he says, but in some people, the sight of an amputee at a very young age may have reinforce the alterations in the brain. About half of people with BIID – itself a condition so rare there aren’t proper estimates of its prevalence – recall having a fascination or close relationship with an amputee while they were a child.
Would Sean contemplate having his limbs amputated? “I would, if it was available,” he says, “but there are no surgeons currently offering the treatment openly.”
"But I am who and what I am in part because of having BIID and my lived experiences. Take away BIID, and I will be a different person. Not necessarily better, nor worse, but different. But the idea of making all my pain go away? It’s definitely appealing."