Electroencephalography (EEG) and magnetoencephalography (MEG) are non-invasive imaging techniques that either directly or indirectly, respectively, measure electrical activity in the brain through electrodes placed on the scalp 24,25. Neuronal oscillations in the classical frequency bands as well as neuronal (de)activations in response to a specific stimulation have now been consistently related to sensory, cognitive, and affective processes 26–29. EEG and MEG are thus valuable techniques for unravelling the neurophysiology underlying nocebo hyperalgesia. Six studies to date have used these methods to examine nocebo-related resting-state or event-specific alterations. Of these 6 studies, 1 used negative suggestion alone 5 and 5 used conditioning methods to induce nocebo hyperalgesia. Conditioning was used with 21 or without 30 negative suggestions, while 2 studies examined conditioning in separate groups either with or without negative suggestions 31,32 and in 1 (MEG) study conditioning was combined with observational learning 15. Albu and Meagher (2016) investigated alterations in EEG activity in a study using negative verbal suggestions regarding inert nocebo and control creams. The nocebo manipulation resulted in a significant increase in thermal pain ratings. Moreover, a significant increase in low alpha EEG power (8-10Hz) was found in the nocebo group relative to the control group when comparing a 5-minute EEG recording during noxious heat stimulation pre- to post-acquisition of the nocebo effect. The exact topography of this finding was not specified. This change in low alpha activity, however, correlated to an increase in pain catastrophizing and not to an increase in pain ratings. Pain catastrophizing in this study was measured via the Pain Catastrophizing Scale 33 that assesses catastrophizing thoughts related to pain, or painrelated worrying 34. The authors suggested that the increase in low alpha power reflects a negative cognitive-affective state in relation to pain, in a process parallel to, or potentially involved in, nocebo hyperalgesia.
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