MIAMI--New findings support the notion that people with dyslexia have problems in a brain region called the cerebellum, psychologists reported here yesterday at the Society for Neuroscience's annual meeting. And for the first time, researchers may now have a simple test that could screen for dyslexia early in life, when alternative teaching methods can help kids overcome dyslexia's obstacles.
Roughly 4% to 10% of children are diagnosed with dyslexia, a failure to learn to read, write, and spell well despite normal intelligence. Some researchers have speculated that the condition might arise from a malfunctioning cerebellum, which guides movement: Many dyslexic children are clumsy and have balance problems, much like people stricken by a cerebellar stroke or tumor. The cerebellum also supports some simple motor learning. Psychologist Rod Nicolson of the University of Sheffield, United Kingdom, has found mild motor problems and reduced blood flow in the cerebellums of dyslexic kids. He suggests that a failure to automatize tasks--to learn to do them quickly and effortlessly--underlies dyslexia's symptoms.
A gauge for cerebellar health is a classical conditioning task, in which subjects--whether humans or rabbits--hear a tone shortly before a puff of air hits their eye. They quickly learn to blink upon hearing the tone--unless certain areas of the cerebellum have been damaged. To see if this could diagnose dyslexia, psychologist Joan Coffin and undergrad Brian L. Jones of King's College in Wilkes-Barre, Pennsylvania, tested 10 college students with dyslexia, five with another learning disorder, and 15 normal readers on the eyeblink task. Normal readers and the learning disabled students made involuntary, anticipatory blinks before the airpuff about 65% of the time. The dyslexic students, however, blinked appropriately only 10% of the time.
The study supports the idea that the cerebellum is involved in dyslexia, says neuropsychologist Markus Schugens of the University of Bochum in Germany. But the neurological underpinnings of dyslexia are still controversial, he notes: Other researchers suspect that sluggish processing of auditory or visual information may lead to dyslexia.
If the eyeblink conditioning task turns out to predict dyslexia reliably, says Coffin, people could easily screen young kids who are having trouble learning to read. The test takes about 30 minutes and the equipment is portable. "This may be a diagnostic method," says Coffin. "And children with dyslexia respond well to early management."