Pavlovian conditioning of muscular responses in chronic pain patients: central and peripheral correlates

Abstract

A differential conditioning design using an aversive slide as conditioned stimulus (CS(+)) that was followed by an intracutaneous electric stimulus to the left index finger as unconditioned stimulus (US) and a pleasant slide that was not followed by shock (CS(-)) were used to test the hypothesis of enhanced aversive conditioning of muscular responses in chronic back pain patients (CBP). Heart rate, skin conductance levels, and integrated surface electromyograms (EMG) from the left and right m. flexor digitorum, the right m. trapezius, and bilaterally from the m. orbicularis oculi were recorded. The electroencephalogram (EEG) was measured from nine electrode positions. The CBP patients showed an enhanced muscular response of the left forearm (where the US was applied) to the CS(+) already in the preconditioning phase. During acquisition both the left forearm and the right trapezius of the patients but not the controls displayed enhanced muscular responding to the CS(+). During extinction the CBP patients' muscular responses to both CS(+) and CS(-) were elevated. The contingent negative variation of the EEG differentiated between CS(+) and CS(-) in the healthy controls but not the chronic pain patients. These data confirm the hypothesis of enhanced muscular responding in chronic pain patients and suggest a dissociation of muscular and central processes during aversive conditioning in the patients that might contribute to the chronicity problem.

New Insights into the Pathophysiology and Treatment of Fibromyalgia

“…In a typical aversive Pavlovian differential delay conditioning procedure, aversive pictures were paired with painful electric stimulation, whereas positive pictures were paired with the absence of shock [32]. CBP patients showed an enhanced muscular response of the left forearm (where the unconditioned stimulus (US) was applied) to the reinforced conditioned stimulus (CS) already in the pre-conditioning phase, indicative of more anticipatory anxiety towards the painful stimulus.…”

Differences in pain-related fear acquisition and generalization

“…Patients with FM were recruited from pain clinics in the regions Flemish-Brabant and Limburg (Belgium) and through a call for participants on the Web site of the Flemish League for FM Patients. Following the procedure of Schneider et al, 51 patients were asked to bring a physically and mentally healthy friend of their own age (range) to the study. The experimental protocol was approved by the Ethical Committee of the Faculty of Psychology and Educational Sciences of the University of Leuven (registration number: S-55100) and the Medical Ethical Committee of the University Hospital of the University of Leuven (registration number: ML9402).…”

Low back pain associates with altered activity of the cerebral cortex prior to arm movements that require postural adjustment

“…With regard to the altered neural functions hypothesized by the kinesiopathologic model, altered cerebrocortical processing of sensory input has been demonstrated, such that people with LBP exhibit an altered amplitude and spatial topography of cerebrocortical somatosensory-evoked potentials to painful or non-painful stimuli (Flor et al, 1997; Wiech et al, 2000; Schneider et al, 2004; Siddall et al, 2006; Diers et al, 2007). Somatosensory-evoked potentials in response to pain stimuli are also modified by background muscle activation in participants with LBP, but not in participants without LBP, suggesting a change with LBP in the neural interactions of pain perception and motor output (Knost et al, 1999).…”