杏吧原创

DISTORTING spectacles can help stroke patients with posture problems to
recover their balance, say researchers in France. They think that the spectacles
reset the patient鈥檚 mental map, and they hope the effect will lead to a
long-lasting cure for some postural problems.

People who have a stroke affecting the brain鈥檚 right hemisphere may suffer
paralysis down their left side and can lean to the right. They may also ignore
things they see or hear on the right. Caroline Tilikete and her colleagues at
the Lyon neurological laboratory of INSERM, the French medical research agency,
gave patients with postural problems spectacles with wedge-shaped prismatic
lenses. These made objects appear 10 degrees farther to the right or the left
than they were.

As expected, when the patients were asked to point to objects they pointed
too far to the left or right, depending on the lens. But when they took the
spectacles off, the researchers found that patients who had been wearing the
right-shifting lenses had lost their postural imbalance. The effect lasted for
several minutes.

The team had previously found that wearing right-shifting lenses for a short
time can correct the tendency of people with right-hemisphere damage to ignore
things on their right. This effect of the lenses can last for days or even
months. 鈥淪urprisingly, this also generalises to the postural system,鈥� says
Tilikete. 鈥淭he speed of the change was impressive.鈥� She hopes the lenses may
lead to lasting improvements in posture.

A clue as to what is going on, she says, lies in the fact that ignoring
sensory inputs or a sense of imbalance are rare in patients with left-hemisphere
damage. The right side of the brain is thought to be the location of our
internal maps of our position in space. Damage to that side of the brain
disturbs the map, says Tilikete. She thinks that distorting the visual input to
the right may recalibrate the map.