So my FINAL blog of the year is inspired by a SONA experiment that I participated in this week…
Prism adaptation is used as a form of neurological rehabilitation generally used to treat hemisphere neglect in stroke patients (more commonly occurring in the right hemisphere). When a patient first looks through prism goggles, the visual field is displaced by varying degrees in the right-hand direction. Most patients typically don’t experience any difference in their normal vision whilst wearing such goggles, and from my own experience this was indeed the case. However the effect soon becomes clear as the majority of goggle wearers can’t point at a visual target accurately – instead an error occurs to the right of the target. Such effects can also occur after the goggles have been removed however, the error occurs in the opposite direction as the visual system tries to correct itself.
Rossetti et al (1998) proposed that adaptation to a distortion could provide an efficient way to stimulate the neural structures involved in sensorimotor transformation. They aimed to study the effect of prism adaptation on neglect symptoms, particularly the shift of the body midline that can occur. All participants who were exposed to the prism distortion to the right improved on their body midline demonstration. The most important finding however was that this improvement lasted for at least 2 hours after the prism goggles were removed, so could potentially be used in stroke rehabilitation programmes.
Pisella, Rode, Farne, Tilikete and Rossetti (2006) explored this effect even further. They found that neglect patients adapt to prism adaptation quicker than non-neglect patients, which can be clearly seen in the diagram below. In particular, the post-test drawings show greater after-effects in neglect patients (their attention to the left hand side of space has been captured, so they are able to attend to, and draw, an additional tree and the house).
It is clear to see that prism adaptation can help neglect patients, and is a hugely successful form of rehabilitation.
Rossetti et al (1998) = http://www.nature.com/nature/journal/v395/n6698/full/395166a0.html?free=2
Pisella, Rode, Farne, Tilikete and Rossetti (2006) = http://www.jsmf.org/meetings/2007/oct-nov/Pisella%20et%20al,%202006.pdf