In 1968 Melzack and Casey described pain in terms of its three “dimensions”:
- Sensory-discriminitive (location, intensity, quality, duration)
- Motivational-affective (suffering and urge to escape the suffering)
By cognitive-evaluation they meant that “higher” cognitive activities such as appraisal, cultural values, distraction and hypnotic suggestion all have a profound effect on the way you experience pain and may modulate the “lower” sensory-discriminative and motivational-affective dimensions (a “top-down” influence) [Melzack, 1986].
The essence of their chapter is captured in this quote:
Pain varies along both sensory-discriminative and motivational-affective dimensions. The magnitude or intensity along these dimensions, moreover, is influenced by cognitive activities such as evaluation of the seriousness of the injury.
Melzack & Casey 1968 p 434
They conclude with a call to action:
Pain can be treated not only by trying to cut down the sensory input by anesthetic block, surgical intervention and the like, but also by influencing the motivational-affective and cognitive factors as well …but the historical emphasis on sensory mechanisms has made these forms of therapy suspect, seemingly fraudulent, almost a sideshow in the mainstream of pain treatment …these methods deserve more attention than they have received.
Melzack & Casey 1968 p 435
Over the last forty years the effect of thinking and motivation on pain has been closely studied and an enormous effort has been put into devising cognitive and behavioural techniques for the amelioration of pain [Vlaeyen & Morley, 2005].
However, the reverse cognitive effect – that is, the effect of pain on cognition and motivation, the “bottom-up” effect – has been virtually ignored. Kreitler and Niv  note that 95% of the papers published on “pain and cognition” deal with the effect of cognition on pain and 5% address the impact of pain on cognition. This field, the effect of pain and other forms of suffering on cognition, is virtually terra incognita.
But Eccleston  has shown that chronic pain impairs control of attention: “… chronic pain patients suffering high intensity pain show significantly impaired performance on an attentionally demanding task when compared to low pain patients and normal controls” [p. 391]. And Astrid von Bueren and colleagues  have found that chronic pain patients exhibit marked deficiencies in alertness, vigilance, visual search and selective attention, compared to the pain free. Bruce Dick and Saifudin Rashiq, in their small recent  study, point to a specific cognitive mechanism, the maintenance of the memory trace, (an element of working memory) that is also impaired by chronic pain. So, pain diminishes working memory and control of attention. These two cognitive functions are, with self-regulation, the essential components of executive function [Royall et al, 2002].
When Harold Merskey and colleagues devised the International Association for the Study of Pain (IASP) definition, they included sensory and emotional components, but made no mention of a cognitive element:
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
Bonica 1979 p 250
The notes to this definition on the IASP website go on to say “It is unquestionably a sensation in a part or parts of the body, but it is also always unpleasant and therefore also an emotional experience” [IASP, 2007].
So, from the point of view of pain science, pain is sensation plus distress, and higher cognition can affect the intensity of the sensation and distress. But it is now becoming clear that pain impairs executive function and heightens sensitivity to affect.
Bonica, J.J. (1979) The need of a taxonomy, Pain, 6:247-252.
Dick, B.D. & Rashiq, M.B. (2007) Disruption of attention and working memory traces in individuals with chronic pain. Anesthesia and Analgesia, 104:1223 – 1229.
Eccleston, C. & Crombez, G. (1999) Pain demands attention: the cognitive-affective model of the interruptive function of pain. Psychological bulletin, 125(3), 356-366.
IASP, International Association for the Study of Pain: Definitions Accessed 9th March 2007.
Kreitler, S. & Niv, D. (2007) Cognitive impairment in chronic pain. Pain: Clinical Updates Vol. IV(4)
Melzack, R. (1986) Neurophysiological foundations of pain, in Sternbach,R.A. (Ed.) The psychology of pain 1-24 Raven Press New York.
Melzack, R. & Casey, K.L. (1968) Sensory, motivational and central control determinants of chronic pain: A new conceptual model. In: The Skin Senses, edited by D.L.Kenshalo, pp. 423 – 443. Springfield, Illinois. Thomas.
Royall, D.R., Lauterbach, E.C., Cummings, J.L., Reeve, A., Rummans, T.A., Kaufer, D.I., LaFrance, W.C. & Coffey, C.E. (2002) Executive control function: a review of its promise and challenges for clinical research. Neuropsychiatry Clin Neurosci 14 (4) 377-405.
Vlaeyen, J.W.S. & Morley, S. (2005) Cognitive-Behavioral Treatments for Chronic Pain: What Works for Whom? Clinical Journal of Pain. Special Topic Series: Cognitive Behavioral Treatment for Chronic Pain 21(1) 1-8
Von Bueren Jarchow, A., Radanov, BP & Jäncke, L. (2006) Pain influences several levels of attention. Zeitschrift fur Neuropsychologie 16 (4) 235 – 42.