[ExI] putting the qual into qualia

[Eugen Leitl]

(beware of VOMIT, tho)

http://www.nejm.org/doi/full/10.1056/NEJMoa1204471

An fMRI-Based Neurologic Signature of Physical Pain

Tor D. Wager, Ph.D., Lauren Y. Atlas, Ph.D., Martin A. Lindquist, Ph.D.,
Mathieu Roy, Ph.D., Choong-Wan Woo, M.A., and Ethan Kross, Ph.D.

N Engl J Med 2013; 368:1388-1397April 11, 2013DOI: 10.1056/NEJMoa1204471

BACKGROUND

Persistent pain is measured by means of self-report, the sole reliance on
which hampers diagnosis and treatment. Functional magnetic resonance imaging
(fMRI) holds promise for identifying objective measures of pain, but brain
measures that are sensitive and specific to physical pain have not yet been
identified.

METHODS

In four studies involving a total of 114 participants, we developed an
fMRI-based measure that predicts pain intensity at the level of the
individual person. In study 1, we used machine-learning analyses to identify
a pattern of fMRI activity across brain regions — a neurologic signature —
that was associated with heat-induced pain. The pattern included the
thalamus, the posterior and anterior insulae, the secondary somatosensory
cortex, the anterior cingulate cortex, the periaqueductal gray matter, and
other regions. In study 2, we tested the sensitivity and specificity of the
signature to pain versus warmth in a new sample. In study 3, we assessed
specificity relative to social pain, which activates many of the same brain
regions as physical pain. In study 4, we assessed the responsiveness of the
measure to the analgesic agent remifentanil.

RESULTS

In study 1, the neurologic signature showed sensitivity and specificity of
94% or more (95% confidence interval [CI], 89 to 98) in discriminating
painful heat from nonpainful warmth, pain anticipation, and pain recall. In
study 2, the signature discriminated between painful heat and nonpainful
warmth with 93% sensitivity and specificity (95% CI, 84 to 100). In study 3,
it discriminated between physical pain and social pain with 85% sensitivity
(95% CI, 76 to 94) and 73% specificity (95% CI, 61 to 84) and with 95%
sensitivity and specificity in a forced-choice test of which of two
conditions was more painful. In study 4, the strength of the signature
response was substantially reduced when remifentanil was administered.

CONCLUSIONS

It is possible to use fMRI to assess pain elicited by noxious heat in healthy
persons. Future studies are needed to assess whether the signature predicts
clinical pain. (Funded by the National Institute on Drug Abuse and others.)