Can Hand Disownership in the Rubber Hand Illusion Reduce Pain?

Simon van RysewykPost-Doctoral Fellow

Graduate Institute of Medical Humanities Taipei Medical University

Pain

‘An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.’ (IASP)

What does this pain definition imply?

Are there other important features of pain?

2RHI Pain

Pain

The multiple components of pain can separate:

• Nociception is not pain

– phantom pain, allodynia, SIA

• Pain sensation is not always painful

– frontal lobotomy, opiate analgesics

The link between pain components is not always strong.

RHI Pain 3

Types of Nociceptive Pain: Superficial

Fast (‘first pain’)

• sharp, pricking

• acute

• skin, muscles, peripheral nerves

• Aδ III fibers

• neospinothalamic

4RHI Pain

Types of Nociceptive Pain: Superficial

Burning

• burning, sore

• acute, chronic

• skin, muscles

• C IV fibers

• archispinothalamic,paleospinothalamic

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Types of Nociceptive Pain: Deep

Slow (‘second pain’)

• dull, aching

• chronic

• viscera, joints, tendons

• C IV fibers

• paleospinothalamic

6RHI Pain

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Nociceptive Pain and the RHI

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Can pain be felt in a rubber hand?

Capelari et al. (2009)

Aim: To study the interaction between vision, touch, proprioception, and pain.

Hypothesis: Nociceptive pain will inhibit the RHI because illusory localization of noxious stimuli may lead to actual tissue damage.

RHI Pain 9

Capelari et al. 2009

Conditions: synchronous, asynchronous (tactile ± nociceptive)

Materials: paint brush, sharp pin

Measures: VAS (0-10 cm, RHI magnitude), Drift, 2 questionnaires (Botvinick & Cohen (1998)

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Capelari et al. 2009

Procedure:

4 min. stroking right index fingers both hands

randomized conditions

questionnaires were completed after the experiment.

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Capelari et al. 2009

Main Results:

80% tactile RHI

77% tactile-nociceptive RHI

Subject RHI sensation mostly in response to visible stimuli.

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Mean VAS and SE per stimulus mode

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Mean VAS and SE for drift per condition

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*p ˂ 0.001

Capelari et al. (2009)

Implications for Pain:

Standard RHI does not inhibit nociceptive pain.

RHI can alter pain-location.

Pain localization involves similar mechanisms to those for innocuous touch.

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Pain Reduction and RHI: Hypothesis

RHI disrupts thermoregulation: ↓ in skin temperature (Moseley et al. 2008)

RHI disrupts immunoregulation: ↑ reactivity to intradermal histamine (Barnsley et al. 2012)

Hypothesis: Since tissue damage threatens homeostasis, RHI may reduce pain.

RHI Pain 16

Mohan et al. 2013

Aim: To study if RHI can reduce pain.

Hypothesis: RHI will have an analgesic effect on pain evoked by noxious stimuli given on the real right hand.

RHI Pain 17

Mohan et al. 2013

Conditions: synchronous, asynchronous (tactile ± noxious or innocuous temperature)

Materials: paint brush, heat probe

Measures: VAS (0-10 cm), de-briefing questionnaire (Botvinick & Cohen, 1998)

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Mohan et al. 2013

Procedure:

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Mohan et al. 2013

Main Results:

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Mean & SE for questionnaire

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Mean & SE for pain ratings

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Mohan et al. 2013

Implications for Pain:

Standard RHI does not reduce nociceptive pain.

Pain components can be independently manipulated.

Pain localization involves similar mechanisms to those for innocuous touch.

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Can Left-Hand RHI Reduce Pain?

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