Different learning disabilities do not correspond to specific regions of the brain, as previously thought, say researchers at the University of Cambridge. Instead poor connectivity between ‘hubs’ within the brain is much more strongly related to children’s difficulties.
Between 14-30% of children and adolescents worldwide have learning difficulties severe enough to require additional support. These difficulties are often associated with cognitive and/or behavioural problems. In some cases, children who are struggling at school receive a formal diagnosis of a specific learning difficulty or disability, such as dyslexia, dyscalculia or developmental language disability, or of a developmental disability such as attention deficit and hyperactivity disorder (ADHD), dyspraxia, or autism.
Scientists have struggled to identify specific areas of the brain that might give rise to these difficulties, with studies implicating myriad brain regions. ADHD, for example, has been linked to the anterior cingulate cortex, caudate nucleus, pallidum, striatum, cerebellum, prefrontal cortex, the premotor cortex and most parts of the parietal lobe.
One potential explanation is that each diagnosis differs so much between one individual and the next, that each involves different combinations of brain regions. However, a more provocative explanation has been proposed by a team of scientists at the MRC Cognition and Brain Sciences Unit, University of Cambridge: there are, in fact, no specific brain areas that cause these difficulties.
To test their hypothesis, the researchers used machine learning to map the brain differences across a group of almost 479 children, 337 of whom had been referred with learning-related cognitive problems and 142 from a comparison sample. The algorithm interpreted data taken from a large battery of cognitive, learning, and behavioural measures, as well as from brain scans taken using magnetic resonance imaging (MRI). The results are published today in Current Biology.
The researchers found that the brain differences did not map onto any labels the children had been given — in other words, there were no brain regions that predicted having ASD or ADHD, for example. More surprisingly, they found that the different brain regions did not even predict specific cognitive difficulties — there was no specific brain deficit for language problems or memory difficulties, for example.
