Thanks to our colleague, Dr. Curt Baxstrom, for resurrecting an article from the journal Neuropsychologia that remains timely nine years after it’s publication: Prisms throw light on developmental disorders, by Brookes, Nicolson, and Fawcett. I can’t post a PDF of the paper due to copyright issues, and couldn’t find an open source hyperlink to the article online, but here is the gist of the experiment:
Participants were instructed to perform 30 trials, throwing clay balls underarm at a target board 2 m wide by 0.8 m high while wearing clear goggles and with their arms occluded by a plastic screen. The target was placed at shoulder height, 2 meters (6 feet) away from the participant. Following the baseline performance condition, subjects donned 30 diopter fresnel yoked prism goggles bases right. The initial aim wearing prisms is theoretically displaced by 60 cm to the left, and adaptation takes place as participants’ throws move in the direction of the target. Immediately post-adaptation, the removal of the prisms causes the participant’s throw to deviate in the opposite direction, the negative after effect.
The researchers discovered that the subjects, all of whom had neurodevelopmental delays including developmental coordination disorder (DCD) and dyslexia, exhibited significantly slower prism adaptation. The slower prism adaptation data are consistent with the cerebellar deficit hypothesis of dyslexia and are difficult to accommodate in any other framework.
A working model based on this research, Dyslexia, Learning, and Pedagogical Neuroscience, was authored by Fawcett and Nicolson. More recently (2012) Nicolson elaborated on this model at the 5th annual Colloque Bourguignon in Dijon, France. And here’s the piece de resistance from that presentation which should be plastered all over the place:
- Forcing automatisation of one subskill (phonics) before the other subskills have matured (executive function, inner speech, eye control, attention) can be disastrous
Nicolson considers “eye control” to consist of eye movements, eye focusing, binocular vision, and the vestibulo-ocular reflex. What role might prismatic Rxing and/or training play in improving cerebellar deficits?