Compassion - Bridging Practice and Science - page 256

(ACC). Finally, the PFC is a large region involved in higher cognitive functions such as volition,
attention and memory[7],which, in terms of pain, is thought to underlie evaluation, appraisal or
memory related to the stimulus[8].Together, a typical neural response to pain generally involves
increased activity of the so-called pain neuro-matrix: SI, SII Thal and INS (reflecting felt intensity),
ACC and INS (reflecting felt unpleasantness) and PFC, thought to reflect memory or stimulus
evaluation. Additional brain regions are involved in modulating painful experience. The so-called
descending modulatory system involves the PFC and deeper brain structures such as the
periaqueductal gray and the rostroventral medulla[9].These areas reduce incoming pain signals by
releasing opioids in the brain. We turn now to the question of how meditative practice might
influence pain perception.
The Basics: How Concentration-Based Meditation May Influence Pain
There are many formulations of Buddhism and a great number of meditative practices. Common to
most lineages is a form of basic training where one learns to wrangle the mind. Such practices are
aimed at calming the often overactive mind by teaching one, among other things, to sustain
attention. Scientifically these practices are referred to as “concentrative” or “focused attention”
meditation techniques [10](seebox VIIandchapter 11). Given that attention alters the way we
perceive things, even these early stages of training may influence pain perception. For example, if
attention is firmly directed to one stimulus it can cause others to go unnoticed. Brain imaging
studies have shown that stimulus-related brain activity is stronger if one is focused on the stimulus.
This holds for pain. Directing one’s attention to a painful stimulus increases brain activity in areas
that process these inputs and importantly also increases the experience of pain[11].Conversely,
distraction can effectively reduce pain, but this depends on how strong and persistent the stimulus
is[12]. A fascinating case study was published in 2005 of a Yogi who claimed to experience no
pain while meditating [13].Researchers applied painful (but safe) laser stimulation to his hand in a
normal waking state and scanned his brain. The procedure was repeated during meditation. Pain-
related regions that were active in the normal state were absent in the meditation scans and,
fittingly, he reported not having felt the stimulation. The meditation practice employed was not
reported but Yogic techniques tend to focus on concentration. One possibility is that he had
learned to deploy his attention so fully in his practice that he cut off conscious perception of other
events; a kind of volitional distraction. While intriguing, too much weight cannot be given to a case
study until it is replicated with a larger sample. Luckily, more modest amounts of practice also
seem to influence pain.
Our work suggests that practicing meditation for several years leads to changes in pain
perception[14], [15], [16].In a preliminary study we recruited a group of Zen meditators and an
age/gender-matched control group[16].During the thresholding procedure prior to the experiment
it became evident that the meditators were much less sensitive to thermal pain (applied to the leg)
than control subjects, requiring much hotter stimuli than controls to report moderate pain. This
finding is consistent with a previous study[17]that showed that learning to meditate increases
tolerance for cold-induced pain. During the experiment, participants were asked to attend to pain in
different ways. The conditions of interest were concentration: try to sustain your attention on the
stimulus at all times, and mindfulness : try to attend moment by moment, without automatic
judgment of the experience as negative or painful. As expected, pain reports were significantly
increased for control subjects during the concentration condition, whereas meditators showed no
change from their own baseline. We speculated that the Zen practitioners may have learned to be
more attentive towards their ongoing experiences in general and therefore, when asked explicitly
to focus, showed no change. This would be consistent with research showing that people perform
attention-demanding tasks with more proficiency after meditative training[18],[19]. However, this
would not explain why they were more tolerant of pain to begin with. In fact, one might expect the
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