No Evidence That Working Memory Modulates the Plasticity of the Nociceptive System, as Measured by Secondary Mechanical Hypersensitivity

Abstract

The effect of cognition on the plasticity of the nociceptive system remains controversial. In this study, we examined whether working memory can buffer against the development of secondary hypersensitivity. Thirty-five healthy women participated in 3 experimental conditions. In each condition, they underwent electrical stimulation of the skin for 2 minutes (middle-frequency electrical stimulation [MFS]), which induces secondary hypersensitivity. During MFS, participants executed either an individually tailored and rewarded n-back task (working memory condition), a rewarded reaction-time task (non-working memory condition), or no task at all (control condition). Before and after MFS, participants rated the self-reported intensity and unpleasantness of mechanical pinprick stimuli. Fear of MFS was also assessed. Heart rate variability was measured to examine potential differences between the 3 conditions and steady-state evoked potentials to the electrical stimulation were recorded to investigate differences in cortical responses. We report no significant difference in hypersensitivity between the 3 conditions. Moreover, engaging in the cognitive tasks did not affect the heart rate variability or the steady-state evoked potentials. Interestingly, higher fear of MFS predicted greater hypersensitivity. In conclusion, we found no evidence that working memory affects the plasticity of the nociceptive system, yet pain-related fear plays a role. PerspectiveThis study shows that the execution of a cognitive task, irrespective of cognitive load or working memory, does not significantly modulate the development of secondary hypersensitivity, heart rate variability, or steady-state evoked potentials. However, higher pain-related fear seems to contribute to greater hypersensitivity.