Affective associative learning modifies the sensory perception of nociceptive stimuli without participant's awareness

Abstract

The present experiment examined the possibility to change the sensory and/or the affective perception of thermal stimuli by an emotional associative learning procedure known to operate without participants' awareness (evaluative conditioning). In a mixed design, an aversive conditioning procedure was compared between subjects to an appetitive conditioning procedure. Both groups were also compared within-subject to a control condition (neutral conditioning). The aversive conditioning was induced by associating non-painful and painful thermal stimuli - delivered on the right forearm - with unpleasant slides. The appetitive conditioning consisted in an association between thermal stimuli - also delivered on the right forearm - and pleasant slides. The control condition consisted in an association between thermal stimuli - delivered for all participants on the left forearm - and neutral slides. The effects of the conditioning procedures on the sensory and affective dimensions were evaluated with visual analogue scale (VAS)-intensity and VAS-unpleasantness. Startle reflex was used as a physiological index of emotional valence disposition. Results confirmed that no participants were aware of the conditioning procedure. After unpleasant slides (aversive conditioning), non-painful and painful thermal stimuli were judged more intense and more unpleasant than when preceded by neutral slides (control condition) or pleasant slides (appetitive conditioning). Despite a strong correlation between the intensity and the unpleasantness scales, effects were weaker for the affective scale and, became statistically non-significant when VAS-intensity was used as covariate. This experiment shows that it is possible to modify the perception of intensity of thermal stimuli by a non-conscious learning procedure based on the transfer of the valence of the unconditioned stimuli (pleasant or unpleasant slides) towards the conditioned stimuli (non-painful and painful thermal stimuli). These results plead for a conception of pain as a conscious output of complex informational processes all of which are not accessible to participants' awareness. Mechanisms by which affective input may influence sensory experience and clinical implications of the present study are discussed.

Emotional Modulation of Pain: Is It the Sensation or What We Recall?

“…Although this may have affected the inability of pleasant pictures to modulate pain, by making them deviate less from neutral data than unpleasant images (Fig. 1), such inability was also found in previous studies that did not eliminate sexual material (Wunsch et al, 2003). Human conditioning theories state that the transfer of affective reactions from an unconditioned to a conditioned stimulus is facilitated when both belong to the same affective category (Cook et al, 1986;Hamm et al, 1989;Ohman and Mineka, 2001).…”

“…A general effect of aversive pictures on behavioral pain responses was shown in previous studies (de Wied and Verbaten, 2001;Meagher et al, 2001;Wunsch et al, 2003). Although human pain scenes were included in these, their specific effect was never assessed.…”

“…Behavioral data indicate that seeing unpleasant pictures illustrating disgust, fear, anger, or pain increase subjective pain intensity (Wunsch et al, 2003) and decrease pain tolerance (de Wied and Verbaten, 2001;Meagher et al, 2001). Although images showing physical suffering were included in these studies, their specific effect on pain was never tested.…”

Visceral pain perception in patients with irritable bowel syndrome and healthy volunteers is affected by the MRI scanner environment

“…[14][15][16]39,40 The majority of evidence has indicated that negative mood or the expectation of increased pain significantly exacerbate pain, whereas positive mood, good coping skills or the expectation of reduced pain prominently attenuate pain. [41][42][43][44][45][46][47] These factors may explain the increased pain reports inside the scanner. Several studies also examined the effect of MR scanner-associated noise on brain activation patterns.…”

Observational Learning and Pain-Related Fear: An Experimental Study With Colored Cold Pressor Tasks

“…Awareness data of two participants were missing. However, data of all participants were included in statistical analyses as contingency awareness is not a necessary feature for differential fear conditioning in pain 52 .…”