Wednesday, 9 May 2007

The woman who sees the world back to front

Imagine if your whole world suddenly went back to front, so that the left-hand side of things appeared on the right and vice versa. That's what happened to a 33-year-old woman, known by psychologists as PR, after a pneumonia-induced coma led her to suffer widespread brain damage.

As PR gradually recovered from her illness, many of her faculties returned to normal, but still she could not read. But then her son noticed that she was able to read perfectly well if he held text up against a mirror. Now Tobias Pflugshaupt and colleagues have observed PR's performance on a number of tests, and found her world appears to be entirely mirror-reversed.

Not only does PR read and write in mirror-reversed fashion, with both letters and whole words reversed, she also finds it easier to tell the time from mirror-reversed clocks, and when asked to draw objects, she portrays them back-to-front. She even reaches for everyday objects such as doors as if they were positioned the other way around from reality. Intriguingly, PR's problem disappears if stimuli are presented to her only very briefly (less than 200ms) – something she had noticed at a nightclub under flashing lights.

The researchers said the case shows how unstable our sense of left and right is – a notion reinforced by the fact young children often confuse left and right and sometimes produce mirror-reversed righting when learning to write. “Generally, mirrored vision can be regarded as an extreme clinical manifestation of this instability”, they said.
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Pflugshaupt, T., Nyffeler, T., von Wartburg, R., Wurtz, P., Luthi, M., Hubl, D., Gutbrod, K., Juengling, F.D., Hess, C.W. & Muri, R.M. (2007). When left becomes right and vice versa: Mirrored vision after cerebral hypoxia. Neuropsychologia, 45, 2078-2091.

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