Neuroscience

I Feel Your Pain, I REALLY Do: Synaesthesia for Another's Pain

"I feel your pain"

Empathy for another person's pain is a hot topic of study in the glamorous field of social cognitive neuroscience. The capacity for empathy supposedly involves mirror neurons, those media darlings of The Young, [The Not-So-Young], and The Neuro:

A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another. Thus, the neuron "mirrors" the behavior of the other, as though the observer were itself acting.

These magical cells have even inspired famous neuroscientists to utter ridiculous hyperbole:

The mirror neurons, it would seem, dissolve the barrier between self and others. I call them "empathy neurons" or "Dalai Llama neurons".

-- MIRROR EURONS AND THE BRAIN IN THE VAT
by V.S. Ramachandran

Synesthesia for pain, a newly described syndrome, goes one step further (Fitzgibbon et al., 2009):

In synaesthesia for pain a person not only empathises with another's pain but experiences the observed or imagined pain as if it was their own. Neural mechanisms potentially involved in synaesthesia for pain include “mirror systems”: neural systems active both when observing an action, or experiencing an emotion or sensation and when executing the same action, or personally experiencing the same emotion or sensation. For example, we may know that someone is in pain in part because observation activates similar neural networks as if we were experiencing that pain ourselves. We propose that synaesthesia for pain may be the result of painful and/or traumatic experiences causing disinhibition in the mirror system underlying empathy for pain.

And what is synesthesia, exactly? According to Edward M. Hubbard's website, SYNESTHESIA can be defined as

...an unusual conscious experience, in which stimulation of one sensory modality leads to a sensory experience in a second, unstimulated sensory modality. For example, seeing letters might lead some people to see colors. Others report that the days of the week or months of the year are arranged like a map in space. Still others report that hearing voices or music cause them to see colors, or that hearing words makes them taste foods...in fact, almost any sensory modality can be involved in synesthesia.

One of the more common forms of synesthesia (illustrated above) is grapheme-color synesthesia, where numbers and letters are consistently associated with specific colors (Ward et al., 2005). A more unusual form is lexical-gustatory synesthesia, in which spoken and written words elicit specific taste sensations that remain constant (Ward & Simner, 2003). For instance, Tony Blair tastes like desiccated coconut.

According to the recent review of the literature by Fitzgibbon et al. (2009), amputees with phantom limb pain comprise the vast majority of those with synaesthesia for pain:

Known Characteristics of Synaesthesia for Pain in a Sample of Amputees with Phantom Pain

Brought on by viewing others in pain and/or observing pain on the television and in movies.
Brought on both when observed pain matches that of the amputated site and/or any general pain
Brought on regardless of the identity of the observed person in pain, i.e. can be a loved one or a stranger.
The experience is similar to the experiences of phantom pain, for example, described as a short sudden ‘electric shock’.
Experienced in the phantom limb and/or stump.

The researchers propose that:

pain experiences may cause disinhibition of mechanisms underlying empathy for pain, resulting in synaesthesia for pain. This proposal is supported by studies that have found mirror activity to be involved in the pain matrix (e.g. Ochsner et al., 2008 and Singer et al., 2004); however, the specific processes that weaken these inhibitory mechanisms are unclear...

Ultimately, in synaesthesia for pain, "there is no self–other distinction in the observation of pain in another person."

References

Fitzgibbon, B., Giummarra, M., Georgiou-Karistianis, N., Enticott, P., & Bradshaw, J. (2009). Shared pain: From empathy to synaesthesia. Neuroscience & Biobehavioral Reviews DOI: 10.1016/j.neubiorev.2009.10.007

Ward J, Simner J. (2003). Lexical-gustatory synaesthesia: linguistic and conceptual factors. Cognition 89:237-61.

Ward J, Simner J, Auyeung V. (2005). A comparison of lexical-gustatory and grapheme-colour synaesthesia. Cognitive Neuropsychology 22:28-41.

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