Imagining missing limbs helps pain, reorganises brain

Neurology journal Brain has just published an elegant open-access study on how just six weeks of mental imagery training can help reduce phantom limb pain as well as reorganising the sensory and motor maps in the brain.

Phantom limbs are when amputees feel sensations that seem to be coming from the missing limb. Sometimes this can include pain which can either be constant or transitory.

Sensations from the nonexistent limb are thought to be due to the brain reorganising the areas which represent the body.

In the case of a phantom arm, for example, the area is no longer receiving sensations from the limb and so stops being so carefully defined. Areas serving other body areas (like the face) start to creep in and facial stimulation can be felt in the missing arm due to the fuzzy neurological boundaries.

This new study, led by neuroscientist Kate McIver, decided to test whether mental imagery can help keep these areas active and prevent the fuzziness creeping in, potentially reducing the phantom pain.

This is based on extensive research to show that imagining something activates similar brain areas to actually perceiving the sensation or executing the action. For example, imagining the sensation of a cool breeze across your arm actually increases activity in the brain areas responsible for arm sensations, while imaging picking something up activates arm-related motor areas.

The research team asked participants to rate their phantom limb pain and used fMRI to look at which brain areas were most active during some movement-related tasks. While in the scanner, the participants were asked to imagine actions with either the existing or phantom hand, to move the existing hand or were asked to purse (push together) their lips.

This last action tends to activate what was previously the hand area in the brain in people with phantom limbs, but doesn’t in people with intact limbs. Indeed, this is exactly what the initial brain scans reported, indicating that their brains had reorganised sensory boundaries.

The researchers then invited each participant for six weekly sessions that involved a mental ‘body scan’ technique that involved imagining free and comfortable movement in their phantom limb such as they could “stretch away the pain” and “allow the fingers, hand and arm to rest in a comfortable position”. Participants also practised in their own time.

After six weeks, pain ratings were taken again and the brain scanning was re-run. The painful sensations had significantly reduced and lip pursing no longer activated the hand area.

The mental imagery seemed to have ‘simulated’ arm actions and sensations well enough so that the neurological boundaries remained sharp and cross-area fuzziness didn’t encourage phantom pain.

Link to full text article in Brain.
Link to PubMed entry.

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