Research into Prism Adaptation…

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

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2 Responses to Research into Prism Adaptation…

  1. psucd8 says:

    Although prism adaption (PA) is used a lot to treat patients from strokes, and can result in a reduction in left bias, it is not always the case. Sarri et al (2009) found that there are specific conditions under which prism adaption does and does not impact on neglect. They found that when using chimeric faces (half with neutral expression, half smiling), presented laterally (one above the other), prism adaption had no impact on the patients’ choice of which faces appeared happiest, as they continued to choose the faces with the smiling half on the right half of the face for the same percentage of trials before and after the PA. However, when the patients had to discriminate between chimeric and nonchimeric faces they performed poorly initially, but some greatly improved at the task after PA. These results suggest that PA does not always work and is not necessarily spatially based as it has no impact on lateral preference tasks.

    Sarri (2009) http://ukpmc.ac.uk/articles/PMC3034025/

  2. Pingback: The final set of comments for year 2! « psucd8

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