Abstract
Mental imagery has the potential to influence perception by directly altering sensory, cognitive, and affective brain activity associated with imagined content. While it is well established that mental imagery can both exacerbate and alleviate acute and chronic pain, it is currently unknown how imagery mechanisms regulate pain perception. For example, studies to date have been unable to determine whether imagery effects depend upon a general redirection of attention away from pain or focused attentional mechanisms. To address these issues, we recorded subjective, behavioral and ERP responses using 64-channel EEG while healthy human participants applied a mental imagery strategy to decrease or increase pain sensations. When imagining a glove covering the forearm, participants reported decreased perceived intensity and unpleasantness, classified fewer high-intensity stimuli as painful, and showed a more conservative response bias. In contrast, when imagining a lesion on the forearm, participants reported increased pain intensity and unpleasantness, classified more low-intensity stimuli as painful, and displayed a more liberal response bias. Using a mass-univariate approach, we further showed differential modulation of the N2 potentials across conditions, with inhibition and facilitation respectively increasing and decreasing N2 amplitudes between 122 and 180ms. Within this time window, source localization associated inhibiting vs. facilitating pain with neural activity in cortical regions involved in cognitive inhibitory control and in the retrieval of semantic information (i.e., right inferior frontal and temporal regions). In contrast, the main sources of neural activity associated with facilitating vs. inhibiting pain were identified in cortical regions typically implicated in salience processing and emotion regulation (i.e., left insular, inferior-middle frontal, supplementary motor and precentral regions). Overall, these findings suggest that the content of a mental image directly alters pain-related decision and evaluative processing to flexibly produce hypoalgesic and hyperalgesic outcomes.
Highlights
Mental imagery – the ability to generate internal representations that preserve the core features of a perceptual experience – relies on similar neural mechanisms as those of actual perception (Kosslyn et al, 2001; McNorgan, 2012)
The present study investigated the neural mechanisms by which mental imagery produces hypoalgesia and hyperalgesia in pain perception
Our results converge towards an interpretation of mental imagery as a flexible tool to alter pain and somatosensory sensations according to specific contextual expectations
Summary
Mental imagery – the ability to generate internal representations that preserve the core features of a perceptual experience – relies on similar neural mechanisms as those of actual perception (Kosslyn et al, 2001; McNorgan, 2012). While the relevance of mental imagery as either a strategy for pain reduction or therapeutic target (as in the case of spontaneous negative images) is well established (Berna et al, 2011), the cognitive and neural mechanisms responsible for imagery-driven modulatory effects on pain perception remain unclear. It is presently unknown whether pain-related mental images influence perception by merely redirecting attention away from the source of pain towards an internal mental image or rather by acting on sensory or affective pain-related processing. We tested whether pain imagery produces specific directional (e.g., hypoalgesic and hyperalgesic) effects, or rather only interferes with pain processing regardless the imagined content
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