Rd. Treede et al., Cortical representation of pain: functional characterization of nociceptive areas near the lateral sulcus, PAIN, 87(2), 2000, pp. 113-119
Many lines of evidence implicate the somatosensory areas near the lateral s
ulcus (Sylvian fissure) in the cortical representation of pain. Anatomical
tracing studies in the monkey show nociceptive projection pathways to the v
icinity of the secondary somatosensory cortex in the parietal operculum, an
d to anterior parts of insular cortex deep inside the Sylvian fissure. Clin
ical observations demonstrate alterations in pain sensation following lesio
ns in these two areas in human parasylvian cortex. Imaging studies in human
s reveal increased blood flow in parasylvian cortex, both contralaterally a
nd ipsilaterally, in response to painful stimuli. Painful stimuli (such as
laser radiant heat) evoke potentials with a scalp maximum at anterior tempo
ral positions (T3 and T4). Several dipole source analyses as well as subdur
al recordings have confirmed that the earliest evoked potential following p
ainful laser stimulation of the skin derives from sources in the parietal o
perculum. Thus, imaging and electrophysiological studies in humans suggest
that parasylvian cortex is activated by painful stimuli, and is one of the
first cortical relay stations in the central processing of these stimuli. T
here is mounting evidence for closely located but separate representations
of pain (deep parietal operculum and anterior insula) and touch (secondary
somatosensory cortex and posterior insula) in parasylvian cortex. This anat
omical separation may be one of the reasons why single unit recordings of n
ociceptive neurons are scarce within regions comprising low-threshold mecha
noreceptive neurons. The functional significance (sensory-discriminative, a
ffective-motivational, cognitive-evaluative) of the closely spaced parasylv
ian cortical areas in acute and chronic pain is only poorly understood. It
is likely that some of these areas are involved in sensory-limbic projectio
n pathways that may subserve the recognition of potentially tissue damaging
stimuli as well as pain memory. (C) 2000 International Association for the
Study of Pain. Published by Elsevier Science B.V. All rights reserved.