Abundant Research Conducted on Humans

Abundant research conducted on humans and animals indicates selective attention as being helpful in reducing pain. Wall and Melzack's (1965) gate control theory implicates cognitive ability in controlling nocicieption. Since Melzack maintained that "specialized systems are involved in the sensory-discriminative, motivational-affective, and evaluative dimensions of pain" (Melzack, 1993, p. 21), Hackett and Horan (1980) attempted to isolate each of these three psychological dimensions: the sensory discriminative (SD), the motivational affective (MA), and the cognitive evaluative (CE) in an experiment conducted on eighy-one undergraduate females. They discovered that the sensory discriminative (SD) as well as the motivational affective (MA) were the most effective, whilst cognitive evaluative showed negligible results. Replicating parts of this experiment on twelve female adolescents using a hot tub, this study showed opposite results to that of Hackett and Horan (1980) in that the sensory-discriminative approach was more effectively able to subsume pain threshold but less effective in dealing with tolerance, whilst the reverse was the case with the motivational. The motivational approach seemed to be more affective in inhibiting pain.

An Experiment on Pain

The earliest well-known proposed theory to pain is that of Descartes who posited that pain traveled through a single channel from the skin to the brain, namely you touched something painful and, instantly, your brain, registering that fact, made you feel an instinctive response. Descartes' theory lingered on until comparatively recently, and, is in fact accepted by the naive layperson as reality; after all, it seems to cohere to experience.

In the 1960s, however, Wall and Melzack's gate control theory (1965), showed that matters can run both ways: the brain registers the pain, but in a downward-spiral of effects, the brain can eliminate that pain too (Ornstein & Swencions, 1990).

Gate Control Theory

Gate control theory proposes that pain processing occurs in an integrated from throughout the neuroaxis and runs through three fundamental regions: the peripheral, spinal, and supraspinal sites. Peripheral pain processing centers around the dorsal horns, supraspinal modulation involves a site called the reticular formation in the medulla and the periaqueductal gray (PAG) area in the midbrain, whilst supraspinal modulation includes areas of the frontal cortex (specifically and most prominently, the amygdala, cingulate cortex, hypothalamus, somatosensory cortex, thalamus, and insular cortex).

Gate control theory, essentially, asserts that basic strategies of pain control can block pain through intervention at the periphery (e.g. with nonsteroidal anti-inflammatory drugs and aspirin), activate inhibitory processes that gate pain at the spinal cord and brain (e.g. By transcutaneous electrical nerve stimulation (TENS), acupuncture, or spinal-cord stimulation), and interfere with the perception of pain at the supraspinal level (e.g. with psychotherapy). These pain interferences, in other words, consists of a combination of mental and physical (i.e., surgical or medical) interventions. Just as afferent draws pain up to mind, so, too, efferent channels can deflect these pain sensations using the same neuro-ability to do so.

At the peripheral level, the myelinated a-delta and beta fibres (two types of afferent axons) conduct cold and well-localized pain sensations, whilst the unmyelinated C. fibres transmit pain that is poorly localized or that is caused by heat or mechanical stimuli.

The a-delta and C. fibres synapse in the dorsal horn of the spinal cord where their neural signals will increase or decrease the flow of impulses to higher processing centers in the central nervous system. Descending inhibitory pathways that are mainly noradrenergic and serotonergic modulated, inhibit the release of substance P. In the substantia gleatinosa (SG). (Substance P. is a pain-relieving neurotransmitter). This is accomplished either directly by the interneurons and/or indirectly by the release of endogenous opiods.

At the same time, synaptic transmission between nociceptors and the dorsal horn neurons is mediated by chemical neurotransmitters that emenate from central sensory nerve endings. This phenomenon depends on the release of glutamate, which produces hyperexcitability throughout the neuroaxis. The ascending pathways -- the spinothalamic, spinoreticular, and spinomesencephalic tracts -- carry messages to supraspinal modulatory centers, where neurons in several regions of the cerebral cortex respond selectively to nociceptive input. The brain's subsequent interpretation of pain is based on the physical pain stimulus and on psychological aspects such as prior experiences with pain, cultural aspects of pain perception and pain expression, and personal attitudes towards pain. The interpretation of pain is then relayed back, in a continuous loop, through the efferent pathways consisting of fibres that connect the reticular formation, midbrain, and SG. In short, Melzack and Wall (*) theorized that nociceptive signals ascending to the upper regions of the brain also elicit signals descending from these same regions and that these could activate neural gating circuits in the spinal cord that may block incoming pain signals (2).

To illustrate, Melzack and Wall (*) quote an experiment by Hilgrad (1973) that shows how 'mind' can subsume pain:

In the normal non-hypnotic state, she [the subject] found the experience of the circulating ice water very painful and distressing. In the hypnotic analgesic state, she reported that she felt no pain and was totally unaware of her hand and arm in the ice water; she was calm throughout. All the while that she was insisting verbally that she felt no pain… the disassociated part of herself was reporting through automatic writing that she felt the pain just as in the normal non-hypnotic state. (p. 46)

This is a very interesting account that signifies that even though the physical representation of pain was obviously present, the subject had transcended that through a unique mental state of mind.

Nowadays, the theory that 'mind' can control pain is popularly accepted. Nonetheless, countless modalities exist, all of which assert themselves to be the most helpful and optimal way to conquer pain.

Since Melzack (1993) had maintained that these "specialized systems are involved in the sensory-discriminative, motivational-affective, and evaluative dimensions of pain" (p. 21), Hackett and Horan (1980) attempted to isolate each of these three psychological dimensions: the sensory discriminative (SD), the motivational affective (MA), and the cognitive evaluative (CE).

In an attempt to investigate which, if any of these pain-inhibiting interventions, were the most helpful, Hackett and Horan (1980) selected the most popular of these pain-control methodologies and divided them into three categories: sensory-discriminative, motivational-affective, and cognitive-evaluative dimensions of pain. Sensory discrimination refers to relaxation training, with an emphasis on the breathing; motivational-affective refers to using the will in exercises such as distraction, visualization, or imaginative transformation, whilst cognitive-emotional consists of cognitive therapy where the person cognitively transmutes the pain in a format of coping statements.

Hacket and Horan (1980) tested the efficacy of each of these interventions by randomly assigning eighty-one undergraduate females to one of the nine treatment conditions, pretesting and then posttesting the participants on the cold pressor. They discovered that cognitive training was less effective in inhibiting the pain as well as in decreasing pain threshold; that sensory training assisted tolerance level but not pain threshold; whilst the motivational approach inhibited pain threshold.

Interested in simulating Hackett and Horan's experiment and interested in seeing which method -- the cognitive or the motivation -- were more effective in mitigating pain, I conducted the following study.

Method

Participants: I randomly selected 12 female acquaintances, all of them adolescents (aged 15-18).

Design: I randomly distributed participants into two groups; each group consisting of 6 members, and randomly assigned each group a different approach: one sensory-discriminative, the other motivational-affective. To each group (separated in a different room), I gave a 15 minutes demonstration of the involved exercises and had them revise their particular exercise. Certain that they knew what to do, I filled the bathroom tub with hot water, so that the temperature reached the highest level, then pre-tested each group by asking them to plunge their hands in whilst focusing on their specific intervention. I observed and timed the maximum amount of time that one or more participants could keep their hands in without removing. I then repeated this experiment in a post trial manner.

Ethics: Participants were warned beforehand about the temperature of the water, and were told that they could withdraw if they wished. Aide from the water temperature, I do not see any other troubling ethical components.

Results

By the pretrial session, most of the participants (with the exception of two) instinctively withdrew their hands, some several times. At the post trial, more were able to keep their hands in at the first try, although all shook their hands violently when removed. Three participants by the sensory discriminative, and four participants by the motivational, removed their hands instinctively by the second try. The motivational group (2 individuals), however, kept their hands in for longer than did those by the sensory-discriminative group. In short, therefore, the average reaction by both approaches showed instinctive removal. Sustained endurance of pain seems to be indicated by the motivational approach.

Discussion

This experiment showed opposite results to that of Hackett and Horan (1980) in that the sensory-discriminative approach was more effectively able to subsume pain threshold but less effective in dealing with tolerance, whilst the reverse was the case with the motivational group. From the fact that two individuals were able to keep their hands in for 5 seconds longer than that of the other participants it seems as though the motivational approach may be more effective than sensory discriminative in quelling pain. Nonetheless, this study is severely limited in that the sample was extremely small, and that I was a biased facilitator (ideally such a study should be conducted with at least three other experimenters who are unaware of the purpose and hypothesis of the study), as well as in the fact that it was conducted in limiting circumstances (the bathroom near a bathtub).

Also to be considered is the fact that other confounding circumstances may have induced the resilient individual to have kept her hands in for longer. She may, for instance, be thicker-skinned than the others, or have some other physiological characteristic that may make her naturally more resilient to pain. Altogether, this experiment would have to be conducted in a far more scientific manner for authoritative and reliable results to be deduced.